[Richard Suchenwirth] 2003-02-25 - [Photo] [image]s can be resized by adding the -zoom or -subsample switches when copying an image. Here is a wrapper that takes only a factor and selects the appropriate switch. The image is scaled in place (so when it is displayed in a widget, updating goes automatically), the temporary image t is freed when no more needed. The following enhanced version is 3 LOC more, but also does flipping around x and/or y axis: proc scaleImage {im xfactor {yfactor 0}} { set mode -subsample if {abs($xfactor) < 1} { set xfactor [expr round(1./$xfactor)] } elseif {$xfactor>=0 && $yfactor>=0} { set mode -zoom } if {$yfactor == 0} {set yfactor $xfactor} set t [image create photo] $t copy $im $im blank $im copy $t -shrink $mode $xfactor $yfactor image delete $t } [WikiDbImage ifilezoom.jpg] Usage examples: adding the following lines gives [iFile: a little file system browser] scaling capacities on the image shown on the "File" page: .m add casc -label Image -menu [menu .m.image -tearoff 0] .m.image add comm -label "Zoom x 3" -command {scaleImage $g(i) 3} .m.image add comm -label "Zoom x 2" -command {scaleImage $g(i) 2} .m.image add comm -label "Zoom x 0.5" -command {scaleImage $g(i) 0.5} .m.image add comm -label "Zoom x 0.33" -command {scaleImage $g(i) 0.33} .m.image add separator .m.image add comm -label "Flip LR" -command {scaleImage $g(i) -1 1} .m.image add comm -label "Flip TB" -command {scaleImage $g(i) 1 -1} .m.image add comm -label "Flip both" -command {scaleImage $g(i) -1 -1} For robustness, one might disable this menu when no image is displayed. Experience shows that enlarging bigger photo images may let the little machine run out of memory - time to throw away some fat MP3 files... ---- [dzach] 16-Sep-2005: Following a suggestion of [suchenwi] in the ''Tcler's chat'', here is a proc to uniformly scale an image in place, using a ratio of integers r1/r2: proc ratscale {img r1 r2} { image create photo tmp_img tmp_img copy $img -zoom $r1 $img blank $img copy tmp_img -subsample $r2 image delete tmp_img } However for large rationals (say 200/255) this may be a memory killer, since it will first zoom the image by 200 and then subsample it (1 every 255). ---- Image scaling also helps in the GIF transparency problem on [iPAQ] - this workaround works: * put an instance of the image in a widget (e.g. a [text]) * zoom up * subsample down again Now transparent pixels are in the widget background color (white), no more random and black, for all instances, and certainly look better than before. foreach i $g(images) { $g(text) image create end -image $g($i) scaleImage $g($i) 3 scaleImage $g($i) .33 } ---- [RS] 2006-02-13: Here's a variation that takes an image and a percentage (see [Greatest common denominator] for gcd), and returns an accordingly scaled image: proc image% {image percent} { set deno [gcd $percent 100] set zoom [expr {$percent/$deno}] set subsample [expr {100/$deno}] set im1 [image create photo] $im1 copy $image -zoom $zoom set im2 [image create photo] $im2 copy $im1 -subsample $subsample image delete $im1 set im2 } proc gcd {u v} {expr {$u? [gcd [expr $v%$u] $u]: $v}} ---- See also [Photo image rotation], [Shrinking an image] For fast arbitrary rotation (and scaling) see: [Enhanced photo image copy command] ---- The combination of photo image zooming and the [Img] extension let us code [A little magnifying glass] in just a few lines. ---- [hypnotoad] Has a C based Tk Image scaler that works with arbitrary sizes: [Image Scaling in C] ---- [Category Image Processing] | [Arts and crafts of Tcl-Tk programming]