GIF partially broken?

[nwin]

This sunflower from makes opening.rs fail with index out of bounds. This is maybe related to #63. The quilt design example on the other hand works…

[ccgn]

i'll look into it

[bvssvni]

Is this fixed?

[nwin]

No.

[bvssvni]

From comment #58 (comment)

The bug is in the LZW decoder and the documentation for LZW is really…brief. This is why I didn't do much on TIFF lately because I also ran into problems with it and couldn't figure out how exactly LZW is supposed to work in detail.

[bvssvni]

Maybe http://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch will help?

[kanetkarster]

I've done some rudimentary testing (about 10 images) and it seems this works with gifs encoded with 89a but fails those encoded with 87a

[nwin]

Interesting finding. I had a look at the specs. At least until decompression it looks like it should be correct and the same for both standards.

[kanetkarster]

I'm wondering if it the dependent on the starting location of the actual image data blocks, based off this documentation

[nwin]

No this doesn't matter. Until the actual image data it is read correctly. As far as I can see every gif 87a image should be a valid gif 89a image.

[nwin]

Maybe there is really something wrong with the reading of the image data blocks. It seems to fail too if the images are too big…