Reads TGA images into an easily manipulatable format. Requires fishpool.easyOps 0.1, which can be found at http://www.fishpool.com/~setok/proj/easyOpers.tcl.

The idea would be to collect a whole series of these under the same namespace for managing different image formats.
 
    namespace import ::easyOps::*
 
 
    # Reads image from file 'filePath', interprets it as a TGA image and
    # returns it as a list that can be used with Tk photos:
    # A list of lists. Each list is one row of the image and contains 
    # pixels in the following format #RRGGBB, with R, G and B being HEX
    # values for red, green and blue, respectively.
 
    proc readData {filePath} {
	set imageFile [open [lindex $filePath 0] r]
	fconfigure $imageFile -translation binary -encoding binary
	set fileData [read $imageFile]
	close $imageFile
 
	array set header [getHeader $fileData]
	array set imageSpec [getImgSpec $fileData]
 
	# Pixels
	# :NOTE: We assume colour map is 0 for now (just deal with 
	# truecolour). 
	# Naughty naughty.
 
	set pixels [string range $fileData [+ 18 $header(idLength)] \
			[+ 18 $header(idLength) \
			     [* $imageSpec(width) \
				  $imageSpec(height) \
				  [/ $imageSpec(pixDepth) 8]] -1]]
 
	# Check order to process pixels in. We always build the list from top 
	# to bottom, left to right.
 
	if {$imageSpec(rightLeft)} {
	    # Image should be draw from right to left
	    set startX $imageSpec(width)
	    set endX -1
	    set incrX -1
	} else {
	    set startX 0
	    set endX [- $imageSpec(width) 1]
	    set incrX 1
	}
 
	if {$imageSpec(topDown)} {
	    # Image should be drawn from top to bottom
	    set startY 0
	    set endY $imageSpec(height)
	    set incrY 1
	} else {
	    set startY [- $imageSpec(height) 1]
	    set endY -1
	    set incrY -1
	}
 
	set imageDat [list]
	for {set y $startY} {$y != $endY} {incr y $incrY} {
	    set row [list]
	    for {set x $startX} {$x != $endX} {incr x $incrX} {
		set idx [* [+ [* $y $imageSpec(width)] $x] 3]
		set rgbString [string range $pixels $idx [+ $idx 2]]
		binary scan $rgbString "ccc" b g r
		set r [& $r 0xFF]
		set g [& $g 0xFF]
		set b [& $b 0xFF]
		lappend row "#[format "%02x%02x%02x" $r $g $b]"
	    }
	    lappend imageDat $row
	}
	
	return $imageDat
    }
 
 
    ## Get image specification.
    ##
    ## 'imgData' contains the full TGA data, including headers.
    ##
    ## Returns key-value list with the following fields: xOrigin, yOrigin
    ## width, height, pixDepth, alpha, rightLeft, topDown.
    ##   xOrigin, yOrigin  Abolute co-ordinates for lower left corner.
    ##   width, height   Hm.. obvious.
    ##   pixDepth  Amount of bits per pixel.
    ##   attrBits   Number of attribute bits per pixel (f.ex. alpha).
    ##   rightLeft   If true, to be drawn from right to left.
    ##   topDown   If true, to be drawn from top to bottom.
 
    proc getImgSpec {imgData} {
	binary scan $imgData "@8 sssscc" imageSpec(xOrigin) \
	    imageSpec(yOrigin) imageSpec(width) imageSpec(height) \
	    imageSpec(pixDepth) \
	    imageDesc
 
	set imageSpec(attrBits) [& $imageDesc 0x7]
	set imageSpec(rightLeft) [>> [& $imageDesc 0x8] 3]
	set imageSpec(topDown) [>> [& $imageDesc 0x16] 4]
 
	return [array get imageSpec]
    }
	 
 
    ## Get image header. 
    ##
    ## 'imgData' contains the full TGA data, including headers.
    ##
    ## Returns key-value list with fields: idLength, colourMap, imageData,
    ## [compression, colourModel].
    ##    idLength   Length in bytes of ID field.
    ##    colourMap  If true, image uses a colour map.
    ##    imageData  If true, header contained image data.
    ##    compression  Compression model, either RLE or none.
    ##    colourModel  Model of colour. Either "mapped", "true-colour" or
    ##                 "black-and-white"
    ## 'compression' and 'colourModel' are only set if 'imageData' is true.
 
    proc getHeader {imgData} {
	set hdrData [string range $imgData 0 18]
	binary scan $hdrData "ccc" header(idLength) header(colourMap) \
	    imageType 
 
	if {$imageType == 0} {
	    # No image data present.
 
	    set header(imageData) false
	    return
	} else {
	    set header(imageData) true
	}
 
	if {$imageType >= 1 && $imageType <= 3} {
	    # No imagecompression
	    set header(compression) none
	} else {
	    set header(compression) RLE
	}
	 
	switch -- $imageType {
	    1 -
	    9 {
		set header(colourModel) mapped
	    } 
	    2 - 
	    10 {
		set header(colourModel) true-colour
	    } 
	    3 -
	    11 {
		set header(colourModel) black-and-white
	    }
	}
 
	return [array get header]
    }
 }

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[Category Graphics]