This is a simple Test Pattern Image Generator that I ([ Andy Gaskell ]) did. I take a set of parameters and generates a canvas and a tiff and bitmap. We were doing hardware debug on a DVI product and needed a wide variety of test images with various hues and colours, so i wrote this script to generate the test image files. I creates three columns, Red, Green and Blue with the tint changing from top (darkest) to bottom (lightest).

The whole code is just pasted in below, it's got a fair few comments in, but any bits that don't make sense, just add a question.

 # Simple script to create test images
 # andy gaskell 11/07/2006
 # test_image_creator.tcl
 
 #load image package
 package require Img
 
 # user configurable vars
 set topcolor 127                ;# top value of colors to go up to (max 256)
 set incrcolor 4                 ;# how many color numbers will each band vary from the previous one
 set spreaddif 18                ;# heigth of the stripes of color
 set outputfilename "test_image" ;# output file name
 
 # util vars
 set count 0
 set spreadcount 1
 
 # GUI setup
 wm title . "Test Image Creator" 
 wm minsize . 800 600
 wm maxsize . 800 600
 frame .w
 canvas .w.image -width 800 -height 600 -background black
 pack .w.image
 pack .w
 .w.image create rect 0 0 800 600 -fill black
 
 # loop making the image
 while { $count < $topcolor } {
 
     # setup the x and y vals for the top left and bottom right corners
     set col1x1 1
     set col1x2 266
     set col1y1 $spreadcount
     set col1y2 [ expr $spreadcount + $spreaddif ]
     set col2x1 267
     set col2x2 532
     set col2y1 $spreadcount
     set col2y2 [ expr $spreadcount + $spreaddif ]
     set col3x1 533
     set col3x2 798
     set col3y1 $spreadcount
     set col3y2 [ expr $spreadcount + $spreaddif ]
      
     # set the colors
     set redvar [format "#%.2X%.2X%.2X" $count 0 0]
     set greenvar [format "#%.2X%.2X%.2X" 0 $count 0]
     set bluevar [format "#%.2X%.2X%.2X" 0 0 $count]
 
     # create the colored boxes
     .w.image create rect $col1x1 $col1y1 $col1x2 $col1y2 -fill $redvar
     .w.image create rect $col2x1 $col2y1 $col2x2 $col2y2 -fill $greenvar
     .w.image create rect $col3x1 $col3y1 $col3x2 $col3y2 -fill $bluevar
 
     # add text to the canvas
     .w.image create text [ expr $col1x1 + 140 ] [ expr $col1y1 + [ expr $spreaddif / 2 ] ] -text "line: [ expr $count / $incrcolor ], colour:  $redvar" -justify left -fill white -font -adobe-helvetica-medium-r-normal-*-10-80-100-100-p-56-iso8859-1
     .w.image create text [ expr $col2x1 + 140 ] [ expr $col2y1 + [ expr $spreaddif / 2 ] ] -text "line: [ expr $count / $incrcolor ], colour:  $greenvar" -justify left -fill white -font -adobe-helvetica-medium-r-normal-*-10-80-100-100-p-56-iso8859-1
     .w.image create text [ expr $col3x1 + 140 ] [ expr $col3y1 + [ expr $spreaddif / 2 ] ] -text "line: [ expr $count / $incrcolor ], colour:  $bluevar" -justify left -fill white -font -adobe-helvetica-medium-r-normal-*-10-80-100-100-p-56-iso8859-1
 
     # increment the counts
     set count [ expr $count + $incrcolor ]
     set spreadcount [ expr $spreadcount + $spreaddif ]
 }
 
 # make sure the GUI updates
 update
 
 # grab the contents of the canvas canvas into photo image testimage.
 set testimage [ image create photo -format window -data .w.image ]
 
 # write the file(s)
 $testimage write -format bmp $outputfilename.bmp
 $testimage write -format tiff $outputfilename.tif
 
 # pop a box
 tk_messageBox -message " Done \n $outputfilename created \n " -type ok -title "Done" -icon info