Bug 300903 – REGRESSION(293871@main): WeChat app allocates large sizes of memory for high resolution images on iOS 26

• Status: RESOLVED
• Resolution: FIXED
• Component: Images

[Said Abou-Hallawa]

The change 293871@main removes setting the value for the key kCGImageSourceSubsampleFactor in the decoding options. This option is very useful when decoding a high resolution image which will be displayed on a much smaller rectangle. ImageIO decodes the image with a smaller rectangle in this case. This saves memory and CPU time.

[Radar WebKit Bug Importer]

<rdar://problem/162787553>

[Said Abou-Hallawa]

Pull request: https://github.com/WebKit/WebKit/pull/52489

[Said Abou-Hallawa]

Here are other repro steps:

1. On macOS lunch mini-browser or Safari
2. Lunch Activity Monitor to monitor the WebKit allocated memory
3. Open https://upload.wikimedia.org/wikipedia/commons/e/ea/Van_Gogh_-_Starry_Night_-_Google_Art_Project.jpg

Result: WebKit allocates about 3GB and it may eventually jetsam and crash
Expected: WebKit allocates about 200-400 MB and it does not jetsam or crash
Note: The size of this image = { 30000 x 23756 }. The memory for decoding this image for its natural size = 30000 x 23756 x 4 = 2.7 GB. But since the window size is much smaller than the natural size of the image, the image should not be decoded for its natural size. This is called image sub-sampling which was dropped by 293871@main.

[EWS]

Committed 301729@main (c4dc35645e7b): <https://commits.webkit.org/301729@main>

Reviewed commits have been landed. Closing PR #52489 and removing active labels.