Bug 230855

Summary:	Canvas memory limit of 4096 × 4096 pixels when calling ctx.getImageData
Product:	WebKit	Reporter:	Bramus <bramus>
Component:	Canvas	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	daniel, dino, ik, kevin_neal, lwarlow, mmaxfield, sabouhallawa, simon.fraser, thorton, vepomoc, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	Safari Technology Preview
Hardware:	Unspecified
OS:	macOS 11
See Also:	https://bugs.webkit.org/show_bug.cgi?id=230887 https://bugs.webkit.org/show_bug.cgi?id=144335

Description Bramus 2021-09-27 13:21:35 PDT

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

Comment 1 Bramus 2021-09-27 13:23:15 PDT

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?

Comment 2 Bramus 2021-09-28 02:40:03 PDT

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.

Comment 3 Kevin Neal 2021-09-29 08:22:24 PDT

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

Comment 4 Radar WebKit Bug Importer 2021-09-29 08:22:34 PDT

<rdar://problem/83671710>

Comment 5 Myles C. Maxfield 2021-10-12 16:45:33 PDT

<rdar://problem/83575501>

Comment 6 Myles C. Maxfield 2021-10-12 16:46:34 PDT

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

Comment 7 Myles C. Maxfield 2021-10-12 16:47:39 PDT

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

Comment 8 Simon Fraser (smfr) 2021-10-12 16:54:33 PDT

Or by the GPU Process?