Blend2d 1.2 - 2024-03-12

• Blend2d-core aligned with Blend2d 0.10.6 (Patch 10-Mar-2024)
• Breaking changes
  • the "contour" method has been extended - for some corner cases, output format has changed.
• New Features
  • Starting with tcltk 8.6.14, a tk-core bug has been fixed
    • "Aqua: XPutImage() swaps red and blue channels"
    • Therefore, from that tcltk release, blend2d works on MacOS, too.
  • BL::Path: added method "reverse"
  • BL::Path: added method "contours"
  • BL::Path: extended method "contour"
    • - length of contours and length of single b-curves
    • - subdivision of contours (uniform length and uniform-t)
    • - curvature
    • - possible incompatibility with previous API
  • Added HSL<-->RGB color conversion.
  • Mtx: added fixed point for xreflection and yreflection,
  • Mtx: added xreflect
• BUG FIX
  • readFromTkphoto & writeToTkPhoto
    • - In some corner cases, incorrect result for the destination region
    • - it MUST have always the same size of the (clipped) source region.
  • readFromTkphoto:
    • - tkphoto with transparencies were not properly handled:
    • - transparent (or semi transparent) pixels MUST be *blended* with the surface
    • - Previously all pixels from tkphoto were simply copied, including the transparent pixels).
• DOCUMENTATION
  • Updated with a full description of the new features.
  • more detailed documentation for methods "readFromTkphoto", "writeToTkphoto"
• TEST-SUITE
  • Updated to cover all new features
• DEMOS
  • Added a lot of new demos.

Blend2d 1.1.1 - 2023-10-31

• Blend2d-core aligned with Blend2d 0.10.5 (Patch 28-Oct-2023)
• Breaking changes
  • gradients: CONICAL renamed as CONIC.
  • Method "BL::Font::textmetrics no more provide the boundingBox details. See the new method "textbox".
• New Features
  • Added new geometry BL::spline
  • Added new geometry BL::textbox
  • Enhanced BL::text with -anchor option
  • Added method BL::Font::textbox
  • Added method BL::font::metrics
  • Added method BL::font::textmetrics
  • Added method BL::Surface::applyTransform
  • Added option "-transformation" to the fill/stroke methods.
  • Added filter "bw" (black&white)
• BUG FIX
  • Removed memory leaks in method "add" of BLPath
• DOCUMENTATION
  • Updated with a full description of the new features.
  • .. plus a lot of corrections.
• TEST-SUITE
  • Updated to cover all new features

Blend2d 1.0.1 - 2023-06-12

• Version 1.0.1 (based on the core Blend2d library ver 0.10.0)
• BUGFIX
  • Shadow filter: temporary surface too large in some cases.
  • FIXED: DirtyArea should be clipped against the base surface.
• FIX
  • Added stackblur.c /.h in SVN repository
• Added demos:
  • sample111.tcl (updated, enhanced)
  • sample112 (new)
  • sample113 (new)
  • sample114 (new)

Blend2d 1.0 - 2023-04-15

• Version bumped to 1.0 (based on the core Blend2d library ver. 0.8)
• New BL::Surface methods:
  • dup
  • rawcopy
  • blur
  • filter (blur, shadow)
• New BL::Path methods:
  • newStrokedPath
• BL::Path enhancements
  • method "add" now accepts also BL::text ... geometries.
  • Text is automatically converted in a set of curves and added to BL::Path. This can be used for transforming a text in a SVG path ..
• BUGFIX
  • option -stroke.dashArray does not accept empty array. Now FIXED
  • option -stroke.join does not accept ROUND as value. Now FIXED
  • method "addSVGpath" not working with the "a" command. Now FIXED
  • method "addSVGpath": type-error for internal method "smoothQuaTO. Now FIXED

Blend2d 1.0b2 - 2020-09-03

• BugFix in Blend2d core (smoothCubicTo)
• DocFix: method "BL::Path lineTo" accepts a sequence of points.
• Extensions: method "BL::Path quadTo" accepts a sequence of 2*N of points.
• Extensions: method "BL::Path cubicTo" accepts a sequence of 3*N of points.
• Extensions: method "BL::Path smoothQuadTo" accepts a sequence of points
• Extensions: method "BL::Path smoothCubicTo" accepts a sequence of 2*N of points
• Added method "BL::Path addSVGpath"
• updated docs and tests
• Added demos
  • sample104-handmade lines
  • sample105-SVGmoby

Blend2d 1.0b1 - 2020-08-12

• First beta release

TclBlend2d is a Tcl package for working with the Blend2d graphics engine.
Blend2d is an open source, high quality, high-performance vector graphics engine

TclBlend2d is a multiplatform binary package including Blend2d library for Windows and Linux; MacOS support is planned.

Images created with TclBlend2d can be saved as BMP files, or exchanged with the tk-photo images.

TclBlend2s provides also a new type of tk-image (named "blend2d") you can embed in your widgets much like a tk-photo image.
You can draw on a "blend2d" tk-image and instantly see the changes in the widgets that have this image attached.

TclBlend2d closely matches the Blend2d C++ API with the exception of cases where a more Tcl-ish way is more appropriate.

DEFINITIONS and CONCEPTS

SURFACES

The main concept of TclBlend2d is the Surface.

A Surface comes with an internal pixmap (32bit depth, with alpha support) and holds all of the graphics state parameters that describe how drawing is to be done. This includes parameters like the current line width, the current color (or gradient), a 2D transformation matrix and many other things.
It allows the actual drawing function to take fewer arguments to simplify the interface.

A Surface implements an immediate-mode rendering; there's no concept of 'scene' or display-list like in the tk-canvas widget; if you want to delete or move a part of the pixmap, you should erase everything and restart drawing from the beginning.

The whole graphic-state can be saved on an internal Surface stack. Any subsequent changes to the graphics state can then be undone quickly by simply restoring the previous graphics-state.

TclBlend2d provides support for simple and complex geometrical entities.
Among the simple geometrical entities, you can find lines, arcs, (rounded) rectangles and many others.
A Path is a complex geometrical entity made of lines and curves (quadratics and cubics Bezier's curves).

A Surface provides just two methods for drawing the geometrical entities: fill and stroke. A geometrical entity can be stroked or filled with a style, i.e a solid color, a gradient, or a pattern.

COLORS, STYLES, and COMPOSITION-OPS

When you stroke/fill a geometrical entity, you are not limited to use an uniform color; when you do a stroke/fill, you apply a style. A style can be

• a uniform color (with alpha transparency)
• a gradient
• a pattern (i.e. a bitmap)

Styles may have their own alpha-transparency, and when you do a fill/stroke, pixels are blended with the pixels already stored in the internal pixmap.

You can set a composition op to control how the new colors are blended with the destination.

MORE on STROKING

TclBlend2d provides support for controlling how a (complex) stroke is rendered: caps, joins, miter, dashes, ...

COORDINATE SYSTEMS and TRANSFORMATIONS

By default the coordinates you specify (user-coords) coincide with the coords of the internal pixmap (pixmap-coords), being (0.0 0.0) the top-left corner.
You can set and combine a transformation matrix (translation, rotation,scale,...), then all the following coordinates you specify with the fill/stroke methods are accordingly multiplied.
These transformations are part of the whole Surface's graphics-state and then they can be pushed on the Surface's stack.

TEXT

TclBlend2d provides support for simple text layout. It can also parse and extract glyphs from the most common font-files.
Glyphs can also be transformed in Path (i.e. set of curves) and then analytically manipulated in terms of contours and single curves.

IMAGES

TClBlend2d has builtin support for reading BMP, PNG and JPG files.
Currently, support for writing is limited to BMP, but you can save the generated image in a tk-photo and then save it in any other format ...

Note that you can import/save just a part of an image (a tk-photo or another Surface), and when you import an image in a Surface, the image is transformed based on the current transformation matrix, i.e. it is properly scaled/rotated.

This concludes this short introduction to the basic features and concepts for working with TclBlend2d.
For further details, read the Getting-started section, look at the demos included with the package, an read the reference manual...

How to create and view an image generated with blend2d ?

Let's create a very simple image with Blend2d

    package require Blend2d
    BL::Surface create mySfc
    mySfc clear
    mySfc fill [BL::circle {200 200} 50] -style [BL::color orange]
    ... you got the idea ...

then we could:

• save it in a file (currently only .BMP is supported)

   mySfc save "./image01.bmp"

• copy the image in a tk-photo

    image create photo photo1
    mySfc writeToTkphoto photo1

... and then embed photo1 in a widget, or save it in a file ...

But we could also create a totally new kind of image that can be embedded in a widget and manipulated in real-time...

You already know how to display a tk-photo in a widget like a canvas or a label. tclBlend2d provides a new type of image named "blend2d".

    image create blend2d mySrf1

"mySrf1" is both a new image and a BL::Surface object (i.e. a command). So, you can embed this image in a widget

    label .a -image mySrf1
    pack .a

and then draw on "mySrf1" ...

    mySrf1 clean
    mySrf1 fill [BL::circle {100 100} 80] -style [BL::color red]
    ...`

You can continue to draw in mySrf1, and instantly see the results in the label-widget.

tclBlend2d 1.2 tclBlend2d Tcl meets Blend2d

Tcl meets Blend2d

SYNOPSIS

package require Tcl 8.6

package require Blend2d ?1.2?

• BL::Surface create sfcName ?options?
• BL::Surface new ?options?
• sfcName destroy
• sfcName dup
• BL::Surface names
• sfcName configure
• sfcName cget optionName
• sfcName configure optionName
• sfcName configure optionName optionValue ?optionName optionValue ...?
• sfcName push
• sfcName pop
• sfcName stacksize
• sfcName reset
• BL::rgb RR GG BB ?alpha?
• BL::color colorName ?alpha?
• HSB hue sat brightness ?alpha?
• HSL hue sat lightness ?alpha?
• BL::gradient type values stopList ?options?
• BL::pattern sfcName|filename ?options?
• BL::line {x0 y0} {x1 y1}
• BL::polyline {x0 y0} {x1 y1} ?{x2 y2} ....?
• BL::polygon {x0 y0} {x1 y1} ?{x2 y2} ....?
• BL::box {x0 y0} {x1 y1}
• BL::rect x y w h
• BL::roundrect x y w h rx ?ry?
• BL::circle {cx cy} r
• BL::ellipse {cx cy} rx ry
• BL::arc {cx cy} rx ry start sweep
• BL::pie {cx cy} rx ry start sweep
• BL::chord {cx cy} rx ry start sweep
• BL::text {x y} font text ?-anchor anchor?
• BL::textbox {x y} font text ?-anchor anchor?
• BL::spline ?mode? {x0 y0} {x1 y1} ?{x2 y2} ....?
• sfcName stroke geometry ?options?
• sfcName fill all|geometry ?options?
• sfcName clear ?options?
• sfcName flush
• sfcName size
• sfcName applyTransform mtx
• sfcName userToMeta
• BL::Path create pathName
• BL::Path new
• pathName destroy
• pathName dup
• BL::Path names
• pathName add geometry ?geometry ...? ?options?
• pathName newStrokedPath ?stroke-options?
• pathName addSVGpath dataString
• pathName apply matrix
• pathName fitTo x y w h
• pathName moveTo point0
• pathName lineTo point ?point ...?
• pathName quadTo p1 p2 ?p1 p2...?
• pathName cubicTo p1 p2 p3 ?p1 p2 p3...?
• pathName smoothQuadTo p2 ?p2...?
• pathName smoothCubicTo p2 p3 ?p2 p3...?
• pathName arcQuadrantTo point1 point2
• pathName arcTo pointC pointR start sweep ?-moveto boolean?
• pathName ellipticArcTo point1 pointR rotation largeArcFlag sweepFlag point1
• pathName close
• pathName reset
• pathName shrink
• pathName bbox
• pathName reverse
• pathName view
• pathName contours ?count?
• pathName contour tolerance ?value?
• pathName contours reset
• pathName contour i|* ?count?
• pathName contour i|* length
• pathName contour i|* isclosed
• pathName contour i|* atlength rLen curveOP
• pathName contour i|* t-subdivision N curveOP
• pathName contour i|* l-subdivision N curveOP
• pathName contour i|* j|* length
• pathName contour i|* j|* atlength rLen curveOP
• pathName contour i|* j|* curveOP t
• pathName contour i|* j|* t-subdivision N curveOP
• pathName contour i|* j|* l-subdivision N curveOP
• BL::FontFace create faceName fontfile ?faceIdx?
• BL::FontFace new fontfile ?faceIdx?
• faceName destroy
• BL::FontFace names
• faceName details
• BL::Font create fontName faceName fontsize
• BL::Font new faceName fontsize
• fontName destroy
• BL::Font names
• fontName metrics
• fontName textmetrics string
• fontName textbox xy text ?-anchor anchor?
• fontName glyphs someText
• fontName glyph glyphIdx
• sfcName blur radius ?-rect {x y w h}?
• sfcName bw ?-luma {r g b}? ?-rect {x y w h}?
• sfcName filter filterType ?filter-args? script
• sfcName load filename
• sfcName save filename ?-format file-format?
• sfcName copy srcSurface ?-from {x0 y0 w h}? ?-to {xp yp}? ?-compop op? ?-globalalpha alpha?
• sfcName copy srcSurface ?-from {x0 y0 w h}? ?-to {x y w h}? ?-compop op? ?-globalalpha alpha?
• sfcName rawcopy srcSurface ?-from {x0 y0 w h}? ?-to {x y w h}? ?-compop op? ?-globalalpha alpha?
• sfcName readFromTkphoto tkphoto ?-from {x0 y0 w h}? ?-to {x0 y0}?
• sfcName writeToTkphoto tkphoto ?-from {x0 y0 w h}? ?-to {x0 y0}?
• image create blend2d ?name? ?options?
• BL::classes
• BL::classinfo objectName
• BL::codecs
• BL::enum
• BL::enum category
• BL::libinfo
• BL::platform
• Mtx::identity
• Mtx::MxM M1 M2
• Mtx::determinant M
• Mtx::invert M
• Mtx::PxM P M
• Mtx::multiPxM Points M
• Mtx::P-P P1 P2
• Mtx::VxM V M
• Mtx::translation dx dy
• Mtx::scale sx ?sx? ?C?
• Mtx::rotation angle radians|degrees ?C?
• Mtx::skew sx sy
• Mtx::xreflection ?x0?
• Mtx::yreflection ?y0?
• Mtx::translate M dx dy
• Mtx::post_translate M dx dy
• Mtx::scaling M sx sy ?C?
• Mtx::post_scaling M sx sy ?C?
• Mtx::rotate M angle radians|degrees ?C?
• Mtx::post_rotate M angle radians|degrees ?C?
• Mtx::xreflect M ?x0?
• Mtx::yreflect M ?y0?
• HSB h s b ?alpha?
• HSL h s l ?alpha?
• RGB2HSB 0xAARRGGBB
• RGB2HSL 0xAARRGGBB

DESCRIPTION

Package Blend2d integrates the Blend2d vector engine in Tcl/Tk. Blend2d is an open source, high-quality, high-performance vector graphics engine. Blend2d is a binary package, distributed in a multi-platform bundle, i.e. it can be used on

• Windows 64 bit
• Linux 64 bit
• MacOS 64 bit (... some limitations ...)

Just an example to get the flavor of how to use Blend2d:

    # draw a circle ...

    package require Blend2d
    set sfc [BL::Surface new]
    $sfc clear
    $sfc configure -fill.style [BL::color orange]
    $sfc fill [BL::circle {150 150} 100]
    $sfc save "./image01.bmp"
    $sfc destroy

Blend2d with and without Tk

You can run Blend2d from a tclsh interpreter, without loading Tk. The following command

package require tclBlend2d

can be used in a tclsh interpreter to load the package without requiring Tk support. You will be still able to generate and save images, but of course, some subcommands related to Tk won't be available. The command

package require tkBlend2d

loads the full package (and requires Tk). Note that

package require Blend2d

is equivalent to

package require tkBlend2d

BL::Surface and the graphics state parameters

The main concept of Tcl-Blend2d is the Surface. A Surface comes with an internal framebuffer (32bit depth, with alpha support) and holds all of the graphics state parameters that describe how drawing is to be done. This includes parameters like the current line width, the current color (or gradient), a 2D transformation matrix and many other things. A Surface can be created with the following commands

BL::Surface create sfcName ?options?

creates a new instance of the class BL::Surface called sfcName. Options can be set at creation time, or later with the configure method.

BL::Surface new ?options?

creates a new instance of the class BL::Surface returning a new unique sfcName. Options can be set at creation time, or later with the configure method.

sfcName destroy

destroys sfcName. Note that in general any oo-object like sfcName should be explicitly destroyed

sfcName dup

duplicates sfcName. Return a new BL::Surface.

Note: the full stack of options is not duplicated; only the current options are duplicated.

BL::Surface names

returns the list of all the currently allocated surfaces. The whole set of Surface's options is also called the drawing state.

A drawing state consists of

• the 2D transformations that have been applied (i.e. translate, rotate, and scale ... see below),
• the current values of various attributes controlling how to fill and how to stroke all the basic and complex geometric entities, and it can be manipulated with the cget/configure methods.

sfcName configure

returns a list with all the valid options and their values.

sfcName cget optionName

returns the current value of the option optionName. Raise an error if optionName is not a valid option.

sfcName configure optionName

returns a list with two values: the named option and its value. Raise an error if optionName is not a valid option.

sfcName configure optionName optionValue ?optionName optionValue ...?

modifies all the named options with the specified values. Raise an error if any optionName is not recognized or its optionValue is not valid; in this case, no option is modified.

Surface options are:

-threads count

If count is >=1 then all the rendering commands are queued and executed by worker-threads when needed (i.e. before exporting an image or, if the surface is a Tkimage, in the event-loop) Default is 0 (i.e all the rendering commands are run immediately (synchronous mode)).

-format {dx dy {?PRGB32 | XRGB32?}}

sets the size (in pixels) and type of the internal framebuffer.

WARNING: When user sets a new -format, the previous content of the framebuffer is lost, and the new framebuffer is uninitialized (it contains garbage). It is user's responsibility to clean it or to properly restore the previous contents. Default is {400 400 PRGB32}

-matrix matrix

matrix defines the affine transformations that will be applied to the next geometric entities specified with the "fill" or "stroke" operations See the section "Affine Matrix" for more details. Default is {1.0 0.0 0.0 1.0 0.0 0.0} (Identity matrix)

-metamatrix

This is a readonly option.

Meta matrix is a core transformation matrix that is normally not changed by transformations applied to the context. Instead, it acts as a secondary matrix used to create the final transformation matrix from meta and user matrices. Meta matrix can be used to scale the whole context for HI-DPI rendering or to change the orientation of the image being rendered, however, the number of use-cases is unlimited. To change the meta-matrix you must first change user-matrix and then call the userToMeta method, which would update meta-matrix and clear user-matrix.

-compop compositionOp

defines how colors should be blended. For further details try googling "Porter-Duff composition" or "Alpha composition". Default value is SRC_OVER.

-globalalpha alphaValue

defines a global alpha value. alphaValue should be between 0.0 (transparent) and 1.0 (opaque). Default value is 1.0

-fill.style style

defines the style to be used for filling. style can be a solid-color (with alpha transparency), a gradient, or a pattern ... Default is 0xFF000000 (Opaque Black).

See the "Setting a style" section below.

-fill.alpha alphaValue

defines the alpha value for fill operations. alphaValue should be between 0.0 (transparent) and 1.0 (opaque). Default value is 1.0

-fill.rule mode

defines how to fill intersecting curves. Default is NON_ZERO

-stroke.style style

defines the style to be used for stroking. style can be a solid-color (with alpha transparency), a gradient, or a pattern. Default is 0xFF000000 (Opaque Black) See above notes for -fill.style

-stroke.alpha alphaValue

defines the alpha value for stroke operations. alphaValue should be between 0.0 (transparent) and 1.0 (opaque). Default value is 1.0

-stroke.width width

defines the width of the strokes (outlines). Default value is 1.0. Note that the stroke width is scaled according to the current matrix transformation. If you want a constant width, independent of the current scale factor, you should set the option -stroke.transformorder to BEFORE.

-stroke.dashoffset offset

defines the offset on the rendering of the associated dash array. Default is 0.0

stroke.join mode

defines how the junction point of two consecutive segments will be stroked. Default is MITER_CLIP

-stroke.miterlimit value

defines the limit on the ratio of the miter length to the stroke-width used to draw a miter join. When the limit is exceeded, the join is converted from a miter to a bevel. Default is 4.0.

-stroke.cap capMode

-stroke.cap {startCap endCap}

capMode specifies how to render the extremities of the stroke. capMode may be a list of two values to specify the startCap and the endCap separately. Default is {BUTT BUTT}

-stroke.transformorder mode

With the default mode AFTER the stroke width will be scaled according to the current transformation matrix. If mode is set to BEFORE, the stroke width won't be scaled. The whole drawing-state can be stored on an internal stack, and you can inspect, save, and restore the whole drawing state (i.e. all the options) with just the following commands:

sfcName push

saves the current graphic-state on an internal stack.

sfcName pop

pops the graphic-state from the stack. Raise an error if stack is empty.

sfcName stacksize

returns the size of the internal stack (i.e. number of saved graphic-states)

sfcName reset

sets the whole surface's graphic-state, including the internal stack. All the options (but -format and -threads) are reset to their default values.

Setting a style

There are 3 types of styles you can set for strokes and fills: SOLID, GRADIENT, PATTERN

• A SOLID style is a uniform color (with optional alpha transparency). It can be specified as a simple hex number in 0xAARRGGBB format, 0xFFFF0000 is red 0xFF0000FF is blue or through the following utilities:

BL::rgb RR GG BB ?alpha?

returns a 0xAARRGGBB color by combining the RR GG BB and the (optional) alpha arguments.

RR, GG, BB are integers 0..255 (best expressed as 0x00..0xFF), alpha is an optional parameter ranging from 0.0 (transparent) to 1.0 (opaque). Default alpha is 1.0

BL::color colorName ?alpha?

returns a 0xAARRGGBB color by combining the colorName and the (optional) alpha arguments.

colorName is a color name (e.g "lightblue") or a numeric-color like #rrggbb, alpha is an optional parameter ranging from 0.0 (transparent) to 1.0 (opaque). Default alpha is 1.0

HSB hue sat brightness ?alpha?

This is an alternative way of specifying a color (HSB model).

HSL hue sat lightness ?alpha?

This is an alternative way of specifying a color (HSL model).

See the "HSB/HSL color models" section at the end for more details.

• A GRADIENT can be specified with the following syntax:

BL::gradient type values stopList ?options?

• type should be one of the following values: LINEAR, RADIAL, CONIC
• values is a list of parameters (depending on type)
• BL::gradient LINEAR {x0 y0 x1 y1} _stopList_ ?_options_?
• BL::gradient RADIAL {x0 y0 x1 y1 radius} _stopList_ ?_options_?
• BL::gradient CONIC {x0 y0 angle} _stopList_ ?_options_?
• stopList is a list of offset and colors (at least two pairs of offset colors)
• offset is a number between 0.0 and 1.0
• color can be expressed as an hex number (0xAARRGGBB) or with the above cited BL::rgb , BL::color, HSB, HSL commands.
• options are:

-mode extendMode

defines how to extend or repeat the style outside the defined region. Default is PAD. See command "BL::enum EXTEND_MODE" for valid values.

-matrix mtx

defines an auxiliary 2D transformation that should be combined with the current transformation matrix. Gradient example:

    # define an oblique LINEAR gradient
    set gr1 [BL::gradient LINEAR  {0 0 400 400} \ 
        [list  0.0 [BL::color lightblue]  0.8 [BL::color blue] 1.0 [BL::rgb 0 0 0 0.1]] \ 
        ]
    $sfc fill [BL::circle {200 200} 100] -style $gr1

• A PATTERN can be specified with the following syntax:

BL::pattern sfcName|filename ?options?

defines a pattern based on another source bitmap, i.e a SfcName, or an external JPEG,PNG,BMP filename.

Valid options are:

-mode extendMode

same as for BL::gradient

-matrix mtx

same as for BL::gradient

-from {x y w h}

defines the pattern based on a rectangular subregion of the srcBitmap. x, y, w,h are pixel coords (integer coords)

Geometric types

Blend2D provides both simple geometric types ( line, rectangle, circle ....) and complex geometric types (Path). The main difference between simple and complex geometry types derives from their implementation. Although all the geometric types could be implemented as oo-classes, this will tend to develop programs difficult to maintain, since in Tcl oo-objects should be explicitly destroyed. Therefore most of the following commands for building geometric types don't return oo-objects but simple tcl-lists/dictionaries, that are automatically disposed when they go out of scope. Currently, just one complex geometry-types (BL::Path) is implemented as oo-class, (and then it's programmers's responsibility to explicitly destroy it). A simple example for drawing a simple geometry is

$sfcName fill [BL::box {0 0} {120 175.8}]

The supported simple-geometries are:

BL::line {x0 y0} {x1 y1}

BL::polyline {x0 y0} {x1 y1} ?{x2 y2} ....?

BL::polygon {x0 y0} {x1 y1} ?{x2 y2} ....?

BL::box {x0 y0} {x1 y1}

BL::rect x y w h

BL::roundrect x y w h rx ?ry?

BL::circle {cx cy} r

BL::ellipse {cx cy} rx ry

BL::arc {cx cy} rx ry start sweep

BL::pie {cx cy} rx ry start sweep

BL::chord {cx cy} rx ry start sweep

BL::text {x y} font text ?-anchor anchor?

The string text, is rendered using font and by default, its anchor-point x y denotes the left-extremity of the text baseline.

It's possible to align the text differently, using the -anchor option, whose possible values are: alignment on the text baseline

• LEFT - anchor the left-extremity of the baseline to xy (DEFAULT)
• MID - anchor the mid-point of the baseline to xy
• RIGHT - anchor the right-extremity of the baseline to xy alignment on the 8 cardinal points of the textbox
• N - anchor the North side of the textbox to xy
• S - anchor the South side of the textbox to xy
• W - anchor the West side of the textbox to xy
• E - anchor the East side of the textbox to xy
• NW - anchor the North-West corner of the textbox to xy
• SW - anchor the South-West corner of the textbox to xy
• NE - anchor the North-East corner of the textbox to xy
• SE - anchor the South-East corner of the textbox to xy
• CENTER - anchor the center of the textbox to xy

BL::textbox {x y} font text ?-anchor anchor?

This geometry simply returns the BL::box of the text. Arguments and options are the same of the above BL::text geometry.

BL::spline ?mode? {x0 y0} {x1 y1} ?{x2 y2} ....?

A spline in its canonical form is a curve going through all its control points, but the first and the last. The first and the last points are just used for defining the tangent of the first interpolated point (i.e. the second control point) and the tangent of the last interpolated point (i.e. the second to last control point). If mode is not specified, then this is a canonical representation and it requires at least 4 points.

If mode is extend, then the control points are implicitly extended by adding a first and last point. In this way, the spline goes through all its explicit control points. Even if mode is closed, then some control points are implicitly added, so that the spline becomes a closed curve. Note that if mode is closed, then the last explicit control point should not be equal to the first explicit control point.

  ...
  $sfc configure -stroke.style [BL::color yellow]
 
   # a minimal canonical spline (4 points): the first and the last point are not drawn
  $sfc stroke [BL::spline {0 0} {100 100} {300 100} {200 200}]
 
   # an extended spline (3 points): all the 3 control points are interpolated
  $sfc stroke [BL::spline extend {100 100} {300 100} {200 200}] 
 
   # a minimal close spline (3 points)
  $sfc stroke [BL::spline close {100 100} {300 100} {200 200}]
   

Note: these splines are C1 cubic Catmull-Rom centripetal splines. Note that all these commands defining simple geometry types start with a lowercase letter. These commands do not create oo-objects; they simply return a specially crafted list that should be passed to the fill/stroke methods. These objects (lists/dictionaries!) don't require an explicit "destroy" method. Other than simple geometries there are complex geometries like BL::Path and they will be described in the following sections.

Drawing on a surface

sfcName stroke geometry ?options?

draws the outline of the specified geometry, according to the current drawing-state. Extra options listed after geometry are temporarily set just for this operation. Note that some options like -stroke.width, -stroke.style, can be abbreviated as -width, -style, and so on.

This method also accepts the option -transformation.

-transformation mtx

applies a temporary transformation to the current coordinate system. Note that this is different from option -matrix; option -transformation applies a transformation mtx to the current coord-sys, whilst options -matrix resets the current coord-sys and sets the mtx transformation.

sfcName fill all|geometry ?options?

draws (fills) the specified geometry, according to the current drawing-state. The special geometry all means "the whole framebuffer". Extra options listed after geometry are temporarily set just for this operation. Note that within this fill operation, the option -fill.style can be abbreviated as -fill.

This method also accepts the option -transformation as for the stroke method.

sfcName clear ?options?

This is a shorthand for "sfcName fill all ?options?"

Other Surface commands

sfcName flush

flushes the internal rendering command queue and waits for its completion (will block). (only useful in Multi-Thread contexts). This command is normally unnecessary, since a flush() is automatically performed before the image is copied/exported/displayed.

sfcName size

returns a list of two values: width and height of the surface (in pixels)

sfcName applyTransform mtx

applies the transformation mtx to the current context's matrix. As a side effect, the context's matrix is changed.

        set M1 [$sfc cget -matrix]
        set M2 [Mtx::rotation 30 degrees]
        $sfc applyTransform $M2
        set M3 [$sfc cget -matrix]
        # -->  M3 == M2*M1

sfcName userToMeta

sets the surface MetaMatrix and resets the UserMatrix

        MetaxMtx <-- UserMtx * MetaMtx
        UserMtx  <-- IdentityMtx

BL::Path

A Path is a complex shape made of b-curves (Bezier curves, including straight lines). The following commands can be used for creating and manipulating a Path:

BL::Path create pathName

creates a new instance of the class BL::Path called pathName.

BL::Path new

creates a new instance of the class BL::Path returning a new unique pathName.

pathName destroy

destroys pathName.

pathName dup

duplicates pathName. Return a new path

BL::Path names

returns the list of the currently available paths

pathName add geometry ?geometry ...? ?options?

adds one or more geometry to pathName. geometry is any geometric type above defined, including the same pathName.

Valid options are:

-direction value

value can be one of NONE, CW, CCW. Default is CW.

Hint: Use CCW for adding holes in a path

-matrix matrix

applies a 2D transformation to the added geometries.

   # starting from Blend2d 1.0, the "add" method also accepts a "BL::text" as a geometry.
   # All the glyphs are converted and added to a BLPath using a simple layout algorithm
  set fontFace [BL::FontFace new "./Arial.ttf"]
  set fontName [BL::Font $fontFace 12.0]
  set blPath [BL::Path new]
  $blPath add [BL::text {100 100} $font "ABC .. Z"]
   # then you can get and manipulate its SVG representation 
  set SVG [$blPath view] 
  ...

pathName newStrokedPath ?stroke-options?

creates a new BL::Path made by stroking the current path with the stroking options passed as arguments. Valid stroke-options are:

-width value

-dasharray value

-dashoffset value

-join value

-cap value

-miterlimit value

-transformorder value

These stroke-options are a subset of the options used for the stroke method of the BL::Surface class.

    # build path0 as a simple triangle
   set path0 [BL::Path new]
   $path0 add [BL::polygon {100 100} {150 200} {200 200}]
    # then derive a new path ... as the previous path but with a thick contour and rounded corners ..'
   set path1 [$path0 newStrokedPath -width 20 -join ROUND]

   ... remember to destroy path0 and path1

pathName addSVGpath dataString

reads and parses the SVG-path-data commands in dataString and adds the equivalent Blend2d command. dataString must follow the rules for the "d" property of the SVG path elements, see the specs at https://www.w3.org/TR/SVG/paths.html#DProperty

    set blPath [BL::Path new]
    # the following SVG-path is presented in this way just for readability  ..
    $blPath addSVGpath "
       M 100 100
       q -100 0 -200 -100
       l 10.0 20.1 30 40 50 -5
       h 1.5e+3
       Z"
    # but it can also be specified in a compact form       
    $blPath addSVGpath "M100+100q-100+0-200-100l10.0,20.1,30,40,50-4H2E+3h1.5e+3Z"

pathName apply matrix

applies the 2D matrix transformation to the whole pathName.

pathName fitTo x y w h

fits (scale&translate) the whole pathName into the given rect.

pathName moveTo point0

sets the starting point0 (expressed as a list of two numbers) for the next commands ..

pathName lineTo point ?point ...?

pathName quadTo p1 p2 ?p1 p2...?

pathName cubicTo p1 p2 p3 ?p1 p2 p3...?

pathName smoothQuadTo p2 ?p2...?

pathName smoothCubicTo p2 p3 ?p2 p3...?

pathName arcQuadrantTo point1 point2

pathName arcTo pointC pointR start sweep ?-moveto boolean?

pathName ellipticArcTo point1 pointR rotation largeArcFlag sweepFlag point1

pathName close

pathName reset

pathName shrink

shrinks the internal capacity of the path to fit the current usage.

pathName bbox

Get the path's bounding-box.

Note that bbox does not consider the line-width, offset, caps (these parameters are defined when stroking/filling the path). If path is empty returns {0.0 0.0 0.0 0.0}

pathName reverse

Reverse each figure (single curve) and their order as well.

pathName view

Returns the path data in SVG format

Path, contours and b-curves

Within a Path, a contour is a sequence of connected b-curves. A non-empty Path may contain one or more contours; contours can be open or closed.

pathName contours ?count?

return the number of contours.

pathName contour tolerance ?value?

get or set the tolerance used for computing the curve length. By default this tolerance is 0.001 meaning that the computed length will have an error less than 0.001 times the actual length.

pathName contours reset

Computing the length of a set of curves is an expensive task and the computed lengths are kept in a cache. This kind of computation is activated only when some specific contour methods are called. This method reset this cache. Note however that when a pathName object is destroyed, all the cache memory is cleaned.

The contour method - operations on contours

pathName contour i|* ?count?

return the number of b-curves of the i-th contour. If * is specified, it returns a list with the number of b-curves of every contour. If contour-index i is out of range, result is {}

pathName contour i|* length

return the length of the i-th contour. If * is specified, it returns a list with the length of each contour. If contour-index i is out of range, result is {}.

Length is calculated using numerical approximation. (see above tolerance).

pathName contour i|* isclosed

return 1 if the i-th contour is closed, else 0. If * is specified, it returns a list with the status (0/1) of each contour. If contour-index i is out of range, result is {} curveOP: The following curveOP can be used for evaluating some properties of each b-curve part of a contour; by using the b-curve's (implicit) parametric equatione B(t), you can evaluate the following curveOP functions at value t (t must be between 0.0 and 1.0):

• at: returns the position {x y} at B(t)
• tangent: returns the tangent versor {x y} at B(t)
• normal: returns the normal versor {x y} at B(t)
• tangentAt: returns the position and the tangent versor at B(t)
• normalAt: returns the position and the normal versor at B(t)
• curvature: returns the curvature at B(t). Curvature is always >= 0. Straight segments have curvature equal to 0.

pathName contour i|* atlength rLen curveOP

rLen is a coefficient (0<=rLen<=1) denoting the relative length of a contour ; 0 corresponds to the start of contour, 0.5 corresponds to the midpoint of the contour (measured along the curves) Depending on the curveOP function (see above), this method returns a point {x y}, a point and a vector {{x y} {dx dy}} or a number.

If contour-index i is out of range, result is {}. If * is specified, it returns a list with the curveOP evaluation at rLen for each contour. Note that if the coefficient T corresponds to a junction-point of two b-curves, the result for the tangent, normal, tangentAt, normalAt, curvature may be undefined (i.e {})

pathName contour i|* t-subdivision N curveOP

generates a sequences of values (evaluating curveOP), by sampling N+1 points on the contour. Points are spaced at parametrically equidistant intervals, meaning that they are closer when the curve has an higher curvature.

If the countour is closed, the last point ((N+1)-th point) coincides with the first one.

pathName contour i|* l-subdivision N curveOP

generates a sequence of N+1 values similar to the above, but points are spaced at intervals of equal length.

The contour method - operations on single b-curves

The following methods require to specify two indices, i and j; i is the contour-index, j is the b-curve-index. As usual, i and j can be '*', meaning 'all contours' and 'all b-curves'.

pathName contour i|* j|* length

return the length of the j-th b-curve of the i-th contour.

If * is specified for the contour-index, the evaluation is performed on each contour, returning a list of values; similarly if the curve-index is *. If * is specified for both the contour-index and the curve-index, this command returns a list of lists, i.e. for every contour returns a list with the lengths of each of its b-curves.

pathName contour i|* j|* atlength rLen curveOP

return the evaluation of curveOP on the j-th b-curve of the i-th contour, at a relative arc-length rLen (rLen equal to 0.5 corresponds to the midpoint of the b-curve). rLen must be between 0.0 an 1.0 If * is specified, the same previous considerations apply.

pathName contour i|* j|* curveOP t

return the evaluation of curveOP on the j-th b-curve of the i-th contour, at t. If * is specified, the same previous considerations apply.

pathName contour i|* j|* t-subdivision N curveOP

generates a sequences of N+1 values evaluating curveOP, by sampling N+1 points on the j-th b-curve of the i-th contour. Points are spaced at parametrically equidistant intervals, meaning that they are closer when the curve has an higher curvature. If * is specified, the same previous considerations apply.

pathName contour i|* j|* l-subdivision N curveOP

generates a sequence of N+1 values similar to the above, but points are spaced at intervals of equal length.

BL::FontFace, BL::Font and Glyphs

Note: Currently text support is still basic and subject to changes. Before drawing some text, you need to load some fonts from an external font-file.

BL::FontFace create faceName fontfile ?faceIdx?

loads a fontfile and creates a new instance of the class BL::FontFace named faceName.

If fontfile is a font collection, you can specify which fontface to load. Default value for faceIdx is 0 (i.e. the first fontface). if faceIdx is greater than the number of the available fontfaces, the last fontface is loaded, and it can be inspected with the details method.

BL::FontFace new fontfile ?faceIdx?

loads a fontfile, creates a new instance of the class BL::FontFace returning a new unique faceName.

faceName destroy

destroys faceName. Note that in general any oo-object like faceName should be explicitly destroyed

BL::FontFace names

returns the list of all the currently allocated fontfaces.

faceName details

returns a dictionary with some properties of the loaded faceName.

These are the currently listed properties; more properties may be added in future Blend2d releases.

  # load the last fontface from a fontfile-collection
  #   ("AmericanTypewriter.ttc" can be found in the tclBlend2d-devkit distribution )
  # Note that I want to load the last fontface, so I specify a large 'faceIdx'
  # surely greater than the available fontface (.. there're 6 fontfaces in this collection ..) 
 set fface [BL::FontFace new "./AmericanTypewriter.ttc" 999]
  # pretty print details
 dict for {key value} [$fface details] {
    puts "[format "%25s %s" $key $value]"
 }
  # ....
  # other ops ...
  #
 $fface destroy

This produces the following output :

                faceIndex 5
               glyphCount 916
                 fullName American Typewriter Condensed Light
               familyName American Typewriter
            subfamilyName Condensed Light
           postScriptName AmericanTypewriter-CondensedLight
               unitsPerEm 1000
                   weight 300
                    style 0
                  stretch 3
    hasCharToGlyphMapping 1 

Once a BL::FontFace has been loaded, and before drawing some text or extracting some glyphs, you should create a BL::Font object based on an instance of BL::FontFace

BL::Font create fontName faceName fontsize

creates a new instance of the class BL::Font, based on faceName, having size fontsize (float).

Note that although any text and glyph can be arbitrarily scaled with the usual 2D transformations, fontsize can be used to select some special glyphs that some fonts may make available for working with very small font sizes.

BL::Font new faceName fontsize

creates a new instance of the class BL::Font returning a new unique fontName.

fontName destroy

destroys fontName. Note that in general any oo-object like fontName should be explicitly destroyed

BL::Font names

returns the list of all the currently allocated fonts.

fontName metrics

returns a dictionary with several font properties (size, ascent, vAscent, descent, vDescent, lineGap, xHeight, capHeight, xMin, yMin, xMax, yMax, underlinePosition, underlineThickness, strikethroughPosition, strikethroughThickness)

fontName textmetrics string

returns a dictionary with the following keys:

• advance - a point
• leadingBearing - a point
• trailingBearing - a point

fontName textbox xy text ?-anchor anchor?

return a list {x0 y0 x1 y1} denoting the bounding box of text. See the details of the AA command for the meaning of various parameters and options A fontName can be used for drawing some text like in the following example

  set fontFace [BL::FontFace new "./Arial.ttf"]
  set fontName [BL::Font $fontFace 12.0]
  set sfc [BL::Surface new]
  $sfc fill [BL::text {100 100} $fontName "Hello World"] -style [BL::color orange]

but it can also used for extracting single glyphs from it.

fontName glyphs someText

returns a list of glyph-indexes, one glyph-index for each (Unicode) character in someText.

fontName glyph glyphIdx

returns a new instance of BL::Path containing the geometrical representation of the given glyphIdx. Raise an error if glyphIdx is invalid.

Note: this method creates a new BL::Pathinstance, and it is user's responsibility to destroy it explicitly. Before drawing some text (or a single glyph) you should load a fontfile, then setup a BL::Font with a given size

    set aFontFace [BL::FontFace new _fontfile_]
    set aFont [BL::Font new $aFontFace _size_]

note that both BL:FontFace and BL::Font create new objects, and therefore it's programmer's responsibility to delete them (e.g call "$aFontFace destroy" ) The easiest way to draw a text on a Surface is to use the special 'geometry' BL::text with the fill/stroke methods

    surfaceName fill [BL::text {10 20} $aFont "Hello World!!"]

Of course you can set the drawing-properties of the Surface as usual (color, gradient, line width, matrix transformation ....) Alternatively, you can extract a single glyph from a font, store it as a BL::Path, and then manipulate it as usual

    set aGlyph [$font glyph 44]  ;# extract glyph n.44
    $sfc stroke $aGlyph

Note that the glyph method returns a new BL::Path object,and therefore it is programmer's responsibility to free the resources (e.g. "$aGlyph destroy" )

Applying filters

TclBlend2d provides two basic ways to work with filters. You can apply a filter to a rectangular region of a Surface (currently only blur and bw filters), or you can set a filter to a script so that it will be applied to all the graphical primitives that will be rendered by this script.

sfcName blur radius ?-rect {x y w h}?

applies a blur filter of size radius (from 2 to 254) to a rectangular region of sfcName

Valid options are:

-rect {x y w h}

defines the rectangular subregion where the filter will be applied. x, y, w,h are pixel coords (integer coords)

If -rect is not specified, the filter will be applied to the whole surface.

sfcName bw ?-luma {r g b}? ?-rect {x y w h}?

applies a black&white filter to a rectangular region of sfcName

Valid options are:

-luma {r g b}

{r g b} are luminance coefficients. Default is {0.2126, 0.7152, 0.0722} (Rec. 709)

-rect {x y w h}

defines the rectangular subregion where the filter will be applied. x, y, w,h are pixel coords (integer coords)

If -rect is not specified, the filter will be applied to the whole surface.

sfcName filter filterType ?filter-args? script

all the graphical primitives created by this script that will be rendered on sfcName will be redirected to a special temporary layer, then the filter will be applied to this temporary layer and then it will be blended with the underlying Surface.

Parameters are:

filterType

Valid values are bw, blur, shadow, and the special filter ignore. This latter filter means that no filter will be applied.

filter-args

A list of options for filterType. (see below .....)

script

A tcl script. Usually, this script should contain some rendering commands on sfcName. All these commands will be temporarily redirected to an automatically allocated temporary Surface. This temporary surface is initialized as a transparent surface and has the same 'state' (e,g the set of options) of sfcName. When script ends, the filter is applied to the whole temporary surface (or better, only to the bounding-box of the rendered primitives), and finally, this temporary Surface will be blended with the underlying sfcName.

Note that if this script changes the state of the (redirected) sfcName, these changes will be also visible in the original sfcName. Warning: take care of not "popping" the initial stack level of sfcName. Method push and pop are allowed within script as long as they are properly paired.

filter-args for "bw" filter

-luma {r g b}

{r g b} are luminance coefficients. Default is {0.2126, 0.7152, 0.0722} (Rec. 709)

filter-args for "blur" filter

-radius radius

blur radius (from 2 to 254). Default is 5 pixels.

filter-args for "shadow" filter

-radius radius

blur radius (from 2 to 254). Default is 5 pixels.

-dxy {dx dy}

dx,dy translation of the blurred shadow. Default is {3 5}

-color color

shadow color. Default is [BL::color gray30]

        $sfc reset
        $sfc clear -style [BL::color white]
         #
         # --- a shadowed blue/white/red disc
         #
        set center {100 150}
        $sfc filter shadow -radius 20 -dxy {5 9} {
                foreach circleRadius {90 60 30} color {lightblue white red} {
                        $sfc fill [BL::circle $center $circleRadius] -style [BL::color $color]                
                }
        }
         #
         # --- three shadowed discs        
         #
        set center {300 150}
        foreach circleRadius {90 60 30} color {lightblue white red} {
                $sfc filter shadow -radius 20 -dxy {5 9} {
                        $sfc fill [BL::circle $center $circleRadius] -style [BL::color $color]                
                }
        }

Exchanging pixmaps

Blend2d provides commands for loading graphics files in a Surface, as well for saving the Surface's internal framebuffer in a graphic file. Blend2d provides commands for copying (part of) the internal framebuffer among different Surfaces. If the Tk support is loaded, that is if you loaded the Blend2d or tkBlend2d packages, you can also exchange parts of the Surfaces framebuffer with tk photo images.

read/write files

sfcName load filename

loads the contents of filename. Supported formats: png, jpeg, bmp.

WARNING: the internal framebuffer is resized.

sfcName save filename ?-format file-format?

saves the internal framebuffer in filename If -format is not specified, this command tries to guess the file-format from the file extension.

NOTE: Currently only BMP and PNG encoders are available

copy among surfaces

sfcName copy srcSurface ?-from {x0 y0 w h}? ?-to {xp yp}? ?-compop op? ?-globalalpha alpha?

sfcName copy srcSurface ?-from {x0 y0 w h}? ?-to {x y w h}? ?-compop op? ?-globalalpha alpha?

copies (a sub-region of) srcSurface to the current sfcName. If no options are specified, this command copies the whole srcSurface starting at coordinates (0,0).

The following options may be specified:

-from {x y w h}

specifies a rectangular sub-region of the surface to be copied. The pixels copied will include the left and top edges of the specified rectangle but not the bottom or right edges. If the -from option is not given, the default is the whole surface.

-to {x y}

specifies where to place the source sub-region in the current surface. The current surface is never resized, therefore, all parts of the srcSurface that will be placed outside this surface will be excluded (clipped).

-to {x y w h}

specifies a rectangular sub-region of the current surface. The source sub-region is scaled to fit into the destination rectangle.

-compop value

applies a composition-operation to the pixels that will be copied. If this option is not specified, the current value of the -compop option is used.

-globalalpha alpha

srcSurface will be blitted using alpha transparency. If this option is not specified, the current value of the -globalalpha option is used. copies (a sub-region of) srcSurface to the current sfcName. If no options are specified, this command copies the whole srcSurface starting at coordinates (0,0).

Note that if there's a matrix-trasformation (rotation, scaling, ..) on the current surface, this transformation will be applied to all points of the destination sub-region (i.e. the -from rectangle will be rotated, scaled, ...)

sfcName rawcopy srcSurface ?-from {x0 y0 w h}? ?-to {x y w h}? ?-compop op? ?-globalalpha alpha?

similar to the copy method. The only difference is that the source region (those specified by the -from option) will be copied in sfcName *without* any transformation.

The default -compop mode is SRC_OVER.

reading/writing tkphoto

These commands require the Blend2d or tkBlend2d package. These commands are not available if you loaded the tclBlend2d package; NOTE: points and rectangles below are specified in pixel-coords. This means that pixels-coords are independent of the current transformation matrix; no rotation or scaling is applied.

sfcName readFromTkphoto tkphoto ?-from {x0 y0 w h}? ?-to {x0 y0}?

copies (a sub-region of) tkphoto to the current sfcName. If no options are specified, this command copies the whole tkphoto to the sfcName coordinates (0,0).

The following options may be specified:

-from {x y w h}

Specifies a rectangular sub-region of the tkphoto to be copied. The pixels copied will include the left and top edges of the specified rectangle but not the bottom or right edges. If the -from option is not given, the whole tkphoto is loaded (clipped against sfcName). x or y can be negative integers.

-to {x y}

Specifies where to place the source sub-region in the current surface. x or y can be negative integers. NOTE: sfcName is not resized; you should take care to resize it in order to get all the portion of the tkphoto you are interested in.

sfcName writeToTkphoto tkphoto ?-from {x0 y0 w h}? ?-to {x0 y0}?

copies (a sub-region of) sfcName to a tkphoto. If no options are specified, this command copies the whole srcSurface to the tkphoto coordinates (0,0).

tkphoto will be expanded to include the the source area, unless the user has specified an explicit image size with the -width and/or -height widget configuration options (see photo(n)); in that case the source area is silently clipped to the image boundaries. The following options may be specified:

-from {x y w h}

Specifies a rectangular sub-region of the surface to be copied. The pixels copied will include the left and top edges of the specified rectangle but not the bottom or right edges. If the -from option is not given, the whole surface is copied to tkphoto. x or y can be negative integers.

-to {x y}

Specifies where to place the source sub-region in the destination tkphoto. x or y can be negative integers.

Creating a blend2d (tk-)image

These commands require the "Blend2d" or "tkBlend2d" package. These commands are not available if you loaded the "tclBlend2d" package;

image create blend2d ?name? ?options?

Similar to the standard command "image create photo ...", this command creates a new image of type blend2d plus a new surface-object that can be used for manipulating the image.

Options are the same options used for the "BL::Surface create .." command. The image can then be embedded in a widget (like a "label" or a "canvas"); every command like fill or stroke issued to the image name, will immediately change the displayed image. Both "image delete sfcName" and "sfcName destroy" can be used to delete the image AND the related surface-object.

Other BL:: commands

BL::classes

lists the name of the BL classes (e.g BL::Surface,BL::Path, ...)

BL::classinfo objectName

returns the class name of objectName. objectName can be any tcloo object (not limited to BL:: objects)

BL::codecs

lists the supported graphics file formats.

For each supported graphic file formats, returns a detailed list made of 5 elements: id, vendor, mimeType, extensions, features.

• id is the key element to be used in load/save operations (e.g. JPEG)
• vendor is the name of the codec's vendor.
• mimetype is a string (e.g. image/jpeg)
• extensions is a sequence of recognized filename-extensions; elements are separated by "|" (e.g. jpg|jpeg|jif|jfi|jfif)
• features is a list of supported features
• READ: reading is supported
• WRITE: writing is supported
• LOSSY: lossy compression
• LOSSLESS: lossless compression
• MULTI_FRAME: multiple frames (GIF).
• IPTC: supported IPTC metadata.
• EXIF: supported EXIF metadata.
• XMP: supported XMP metadata.

BL::enum

lists all the enum categories

BL::enum category

lists all the values for that _category_ e.g. BL::enum GRADIENT_TYPE --> LINEAR RADIAL CONIC

BL::libinfo

returns a dictionary with info about the core Blend2d library. The dictionary keys are version, type (build-type)

BL::platform

returns a dictionary with info about the cpu architecture and the cpu features used by Blend2d. The dictionary keys are cpuArch, cpuFeatures, coreCount.

Auxiliary utilities

Blend2d provides some small helpers for working with transformation-matrix and colors

Affine matrix

An affine matrix is a 3x3 matrix whose last column is fixed 0 0 1

    a b 0
    c d 0
    e f 1

Given this rule, it is convenient to express such matrices as a list of 6 numbers { a b c d e f } instead of 9 numbers. Working with these matrices can be simplified by using the Mtx package included in Blend2D. In the following paragraphs "M" stands for a matrix (a list of 6 numbers), "P" stands for a 2D point (a list of 2 numbers). The following ops are supported

Mtx::identity

returns the identity matrix {1 0 0 1 0 0}

Mtx::MxM M1 M2

matrix multiplication

Mtx::determinant M

Mtx::invert M

matrix inversion - Raise an error if M is not invertible.

Mtx::PxM P M

map a Point

Mtx::multiPxM Points M

map a list of Points

Mtx::P-P P1 P2

return P1-P2

Mtx::VxM V M

map a vector V : VxM(V,M) = PxM(V,M)-PxM(0,M)

Mtx::translation dx dy

Mtx::scale sx ?sx? ?C?

scale sx sy around the fixed-point C (C default is {0 0})

Mtx::rotation angle radians|degrees ?C?

performs a rotation of angle around the fixed-point C (C default is {0 0})

Mtx::skew sx sy

Mtx::xreflection ?x0?

reflection with respect to the vertical axis x=x0 (default x0 is 0)

Mtx::yreflection ?y0?

reflection with respect to the horizontal axis y=y0 (default y0 is 0)

Mtx::translate M dx dy

Mtx::post_translate M dx dy

Mtx::scaling M sx sy ?C?

Mtx::post_scaling M sx sy ?C?

Mtx::rotate M angle radians|degrees ?C?

Mtx::post_rotate M angle radians|degrees ?C?

Mtx::xreflect M ?x0?

Mtx::yreflect M ?y0?

HSB/HSL color model

Blend2d internally works with colors expressed in terms of red,green,blue and alpha channels, but in some cases it is more natural to express color following the HSB or HSL color model, where:

• h (hue) is a 0.0..360.0 angle
• s (saturation) is 0.0 .. 1.0
• b (brigthness) is 0.0 .. 1.0 ( 0 is black, 1 is white ) or
• l (lightness) is 0.0 .. 1.0 ( 0 is black, 1 is white )
• alpha is 0.0 .. 1.0 See https://en.wikipedia.org/wiki/HSL_and_HSV for details.

The following commands are available for converting between between ARGB and HSB or HSL color models.

HSB h s b ?alpha?

returns an ARGB number (in decimal notation, not in hex notation)

HSL h s l ?alpha?

returns an ARGB number (in decimal notation, not in hex notation)

RGB2HSB 0xAARRGGBB

returns a list with the HSB components. { h s b alpha }

RGB2HSL 0xAARRGGBB

returns a list with the HSL components. { h s l alpha }

Limitations

• Saving a Surface is currently limited to BMP or PNG files.
• The -stroke.dasharray option is currently a no-op.

KEYWORDS

graphics

CATEGORY

vector graphics

COPYRIGHT

 Copyright (c) 2021..2024 - A.Buratti

ABU 12-Jul-2020

TclTk binding for Blend2d is almost ready .. Just some fixing for the last Blend2d features (multithread rendering) and for a more tcl-ish API.

In the meantime, you can play with the new pixmix 2.x demos. pixmix includes a preliminary tcl-Blend2d engine and, although Blend2d is a vector graphics engine, it provides amazing performances even for working with large (fullscreen) bitmaps.

ABU 18-Oct-2019

Blend2D is a high-performance 2D vector graphics engine. See https://blend2d.com

Credits to https://ciechanow.ski/alpha-compositing/

TclTk binding is still at alpha stage, performances are amazing.

Here is a demo screenshot. Rotation/zoom at full-screen resolution in real-time (no flickering)

More to come..