http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/image.htm

Tk images fall in two categories: [bitmap] and [photo].

[[Insert information about Tk's image command, the practical uses, and
the little things that can get you, here]]

One warning- be very careful what names you use for the image command.
In particular, it is not advised that user input be used.  This is because
when Tk's image command creates an image, any proc/command formerly using
that name is replaced.  This could be frustrating or even disasterous
if a user provided a name such as [set] or [interp], etc.

----
The Tk image command provides support for a limited number of formats.
TkImg (aka [Img]) is a widely-used extension that beefs up image's
capabilities.  Note that
    $image write ...
can write [GIF] and [PPM], but
    $image data ...
cannot.

----

[KBK] offers an example which relies on [base64] to embed GIFs in scripts:
    package require base64
    $img write myimage.gif -format gif
    set f [open myimage.gif r]
    set data [read $f]
    close $f
    set script [list set img \
        [list image create photo -data [base64::encode $data]]]
Img turns this into a one-liner:
    % package require Img
    1.2.4
    % set i1 [image create photo -file \
        [file join $::tk_library demos images earthris.gif]]
    image2
    % set s1 [$i1 data -format gif]; string length $s1
    15192
    % rename $i1 {}
    % set i2 [image create photo -data $s1]
    image3


Img does much beyond this, including [[insert details here ... ]] and [[...]].

----
I ([FW]) wrote this code in a couple minutes the other day to occupy myself, which generates a 500x500 image of randomly-colored pixels and displays it in a window.  I think this summarizes Tcl's image generation capabilities well (and the images it makes are pretty mesmerising, too).  Might as well put it up here:

 proc generate_data {} {
   set data [list]
   for {set x 0} {$x < 500} {incr x} {
     set row [list]
     for {set y 0} {$y < 500} {incr y} {
       lappend row [format "#%02x%02x%02x" [random_byte] [random_byte] [random_byte]]
     }
     lappend data $row
   }
   return $data
 }
 
 proc random_byte {} {
   return [expr {int(rand() * 256)}]
 }
 
 set image [image create photo] 
 $image put [generate_data]
 
 label .l -image $image
 pack .l
[RS]: Cool! In my copy I just added the line
 bind . <Return> {$image put [generate_data]}
to let the CPU work more ;-)

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''[MGS]'' [[2003/09/15]] - Note that '''image create''' will overwrite existing images of the form '''image'''''x'', where ''x'' is an integer:

 % image create photo image1
 image1
 % image create photo
 image1

It appears that Tk uses an internal counter for image names, and does not check if '''image'''''x'' already exists.

In fact, Tcl in many cases does not prevent one from creating ''objects'' that are named the same as an existing one.  The difference here is that Tk is automatically generating a name that happens to match.  '''That''' is the unfortunate ''feature''.

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See also
   * [Buttons with image and text]
   * [Images With Transparency and Plain Images]
   * [Reading GIF image dimensions]
   * [Reading JPEG image dimensions]
   * [Reading PNG image dimensions]
   * [Tk image Dos and Don'ts] 
   * [Image scaling]
   * [Serializing a bitmap]
   * [Serializing a photo]
   * [Generating a color image]
   * [Coloring a gray image]

----
[Tk syntax help] - [Arts and Crafts of Tcl-Tk Programming] - [Category Command]
- [Category Graphics]