[PYTHON IMAGE-SIG] Transparent GIF images & Tk

[Fred L. Drake]

> A reasonable attempt, but the color parameter gets lost on its way
> down to the C code.  Joel Shprentz reported this out a while ago, but
> the fix didn't make it into the latest release (sorry, Joel).  I'll
> try fixing it to the next release.

  Hmm....  I couldn't quite figure out where the color value gets
lost, so I'll wait for your fix on that.
  The subscript operator on the image objects defined in
_imagingmodule.c is broken:  in the function image_item(), the line:

	y = i / im->ysize;

should be changed to:

	y = i / im->xsize;

  With this change, I can sometimes get tolerable results with this
function:


def transp_gif_to_rgb(im, (r, g, b)):
    """Translate a P-mode GIF with transparency to an RGB image.

    im
	The GIF image.

    (r, g, b)
	The RGB-value to use for the transparent areas.  These should be
	8 bits for each band.
    """
    # This is really quite slow.
    bg = im.info["background"]
    rgbimg = Image.new("RGB", im.size, (r<<24 | g <<16 | b<<8))
    mask = Image.new("1", im.size)
    drawing = ImageDraw.ImageDraw(mask)
    getpixel = im.getpixel
    point = drawing.point
    yrange = range(im.size[1])
    ylength = im.size[1]
    for x in range(im.size[0]):
	for pos in map(None, [x]*ylength, yrange):
	    if getpixel(pos) != bg:
		point(pos)
    rgbimg.paste(im, None, mask)
    return rgbimg




  -Fred

--
Fred L. Drake, Jr.
fdrake@cnri.reston.va.us
Corporation for National Research Initiatives
1895 Preston White Drive
Reston, VA    20191-5434

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