Bug 230855 – Canvas memory limit of 4096 × 4096 pixels when calling ctx.getImageData

• Status: NEW
• Component: Canvas

[Bramus]

Spotted on Twitter [1], by Rik Schennink

“Safari 15 has a canvas memory limit of 4096 × 4096 pixels where Safari 14 could deal with resolutions up to 16384 x 16384”

Can verify via the CodePen Demo [2] Rik also shared, in which he creates a 4097x4097 canvas. Upon calling `ctx.getImageData(0, 0, size, size)` the code fails.

“Unable to get image data from canvas. Requested size was 4097 x 4097”

While searching for bugs I did find [3] where the limit was added for iOS, but this is now applied on macOS too apparently. Is this a regression?

[1] https://twitter.com/rikschennink/status/1442443774748082185
[2] https://codepen.io/rikschennink/pen/YzQRdwZ
[3] https://bugs.webkit.org/show_bug.cgi?id=145998

[Bramus]

I read in https://bugs.webkit.org/show_bug.cgi?id=229237 that the “2D memory limit” test got marked as expected to Crash, so I guess that that explains why this went undetected?

[Bramus]

Update: Creating a canvas of 16384 x 16384 on macOS and drawing on it still works. It's only when calling `ctx.getImageData` that Safari fails to cooperate.

[Kevin Neal]

Thank you for filing. The appropriate engineers have been notified.

[Radar WebKit Bug Importer]

<rdar://problem/83671710>

[Myles C. Maxfield]

<rdar://problem/83575501>

[Myles C. Maxfield]

static const float MaxClampedLength = 4096;
static const float MaxClampedArea = MaxClampedLength * MaxClampedLength;

[Myles C. Maxfield]

Might have been caused by https://bugs.webkit.org/show_bug.cgi?id=144335?

[Simon Fraser (smfr)]

Or by the GPU Process?