Fail to save large AVIF image

[vinlyx]

pillow-avif-plugin/src/pillow_avif/_avif.c

Line 483 in ac4789d

"rgb data is incorrect size: %u * %u (%u) != %zd",

Hi @fdintino,
I am trying to use avif plugin to convert a large TIFF image to AVIF format. Unfortunately, I got a RuntimeError:
File "/xxx/Python-3.9.4/lib/python3.9/site-packages/pillow_avif/AvifImagePlugin.py", line 240, in _save
enc.add(
RuntimeError: rgb data is incorrect size: 119151 * 49716 (1628743820) != 5923711116

The raw TIFF image is 39717 x 49716 in RGB mode. I have tried to debug the error and find out it may due to an uint32 overflow issue. The width and height of avifRGBImage are defined as uint32_t. In this case 39717 x 49716 is larage than 4,294,967,295, so it generate a overflowed result (1628743820).

if (rgb.rowBytes * rgb.height != size) {
Convert rgb.rowBytes or rgb.height uint64_t during this operation may fix the issue, but I am not sure whether it will cause any issue in the following step.

Hope this analysis will help to fix this error. Thanks!

[fdintino]

rgb.rowBytes and rgb.height are uint32_t in libavif, and I believe the width and height themselves have limits well below 2³². But we can cast them to Py_ssize_t in that multiplication expression to fix this specific overflow.

[fdintino]

So...I can fix the issue in this plugin. But it appears that libavif has a limit of 16384x16384 (2²⁸ pixels). So although encoding your image would no longer fail with this particular error, you still would not be able to encode the image as AVIF.

[cdgriffith]

Just adding a detail that the specifications don't allow for huge images with AV1.

NOTE: Following [AV1] level definitions, coded image items compliant to the AVIF Advanced profile may not have a number of pixels greater than 35651584, a width greater than 16384 or a height greater than 8704. It is still possible to use the Advanced profile to create larger images using grid derivation.

I do not see further reference to how to achieve a "grid derivation" AVIF image.

[fdintino]

libavif supports image grids...I had been meaning to look into exposing that in the codec. I'll see what I can do.

[vinlyx]

libavif supports image grids...I had been meaning to look into exposing that in the codec. I'll see what I can do.

That would be amazing~!
But I know little about image grids feature. Is there any documentation or example about that? Thanks!

[vsdfrf]

Hello, I find that libavif may support large images, Does that mean that using the avif plugin to convert a large TIFF image to AVIF format is possible?