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ID | Category | Severity | Reproducibility | Date Submitted | Last Update | ||||
0001388 | [Squeak] Graphics | minor | always | 06-28-05 21:06 | 02-25-06 23:51 | ||||
Reporter | tb | View Status | public | ||||||
Assigned To | andreas | ||||||||
Priority | normal | Resolution | fixed | ||||||
Status | closed | Product Version | 3.8 | ||||||
Summary | 0001388: [BUG] GIFReadWriter - degradation on writing | ||||||||
Description |
I don't know a whole lot about image file formats but I've noticed that gifs written with GIFReadWriter end up looking worse than when they were read. The (hopefully still) attached image illustrates the problem. The leftmost image is the original gif. The rightmost is what the imported gif looks like when displayed in a SketchMorph. They both look pretty good. The middle one is what you get if you write the form back out as a gif. It looks a whole lot worse. |
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(0001688 - 217 - 217 - 217 - 217 - 217 - 217) KenCausey 06-28-05 21:08 |
I moved this report from BFAV2. The original report has a PDF attached which as mentioned in followups to that report was not really a useful way to examine the problem so I didn't bother to post the attachment here. |
(0001689 - 256 - 296 - 337 - 337 - 337 - 337) KenCausey 06-28-05 21:08 |
Duane Maxwell <dmaxwell@san.rr.com>: "Looks to me like it wrote the GIF out with a fixed 8-bit palette, not one optimized for that graphic, unlike the original GIF. It looks OK in Squeak probably because it was being displayed in a truecolor Form." |
(0001690 - 392 - 460 - 501 - 501 - 501 - 501) KenCausey 06-28-05 21:09 |
"Andreas Raab" <andreas.raab@gmx.de>: "Interesting. That's a bug. GIFReadWriter tries to reduce the color count of the image being written (e.g., when you write form > 8bpp) and apparently that's broken for ColorForm. It's not quite clear how to fix this though. We either need to find out what breaks in colorReduced and/or simply disable the call in GIFReadWriter for forms <= 8bpp." |
(0001691 - 176 - 204 - 204 - 204 - 204 - 204) KenCausey 06-28-05 21:09 |
tblanchard@mac.com: "Is this still likely to be true if the ColorForm reports its depth as 8 anyhow? Because that's what happens - the gif imports to an 8 bit ColorForm." |
(0001692 - 272 - 334 - 375 - 375 - 375 - 375) KenCausey 06-28-05 21:09 |
"Andreas Raab" <andreas.raab@gmx.de>: "If the gif imports it to an 8 bit ColorForm and given that we see the degradation, I would claim that it is _certain_ that it is still true if the ColorForm reports its depth as 8 anyhow ;-) What was your question again? ;-)" |
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