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Re: NSImageRGBColorTable crash
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Re: NSImageRGBColorTable crash


  • Subject: Re: NSImageRGBColorTable crash
  • From: David Remahl <email@hidden>
  • Date: Tue, 20 Apr 2004 01:34:48 +0200

On 20 apr 2004, at 00.34, Glenn Andreas wrote:

At 11:22 PM +0200 4/19/04, David Remahl wrote:
[[Resend, because the message didn't appear on the list the first time...]]

Has anyone had any success with using NSImageRGBColorTable to generate GIFs?

If tmp is a 768 byte file, containing a color lookup table, the following will crash:

Have you tried a valid color lookup table?

% python -c 'f=open("/tmp/clut","w"); f.write("\xff"*768); f.close()' # create a 768 byte file filled with FF.


This would just be a single color (I forget if 0xffffff is white or black for GIF files), which would make it impossible to do any sort of dithering (which is where it is crashing).

I'd at least try something like:

python -c 'f = open("/tmp/clut","w"); for i in range(0,255): f.write("%c%c%c" % (i,i,i))'

which would produce a grayscale ramp to at least give it somethign useful to dither...

Yes, I did start off with using a valid color table (the all-white one was just for demonstration)...It wasn't quite as regular as the ramp one, because it was generated by the neuquant algorithm, so I should have thought of using a more typical one. I also explicitly turned off dithering, and still got the crash.

I have now tried the grayscale one, and it still crashes in ComputeDither (even with dithering turned off...).

/ Regards, David
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  • Follow-Ups:
    • Re: NSImageRGBColorTable crash
      • From: Glenn Andreas <email@hidden>
References: 
 >NSImageRGBColorTable crash (From: David Remahl <email@hidden>)
 >Re: NSImageRGBColorTable crash (From: Glenn Andreas <email@hidden>)

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