11431 2010-11-30 01:11:46 +0000 should mention that .toDataURL() for image/jpeg acts as if the image was composited against black 2011-09-29 08:16:44 +0000 1 1 1 Unclassified HTML WG LC1 HTML5 spec unspecified Other other RESOLVED WONTFIX http://www.whatwg.org/specs/web-apps/current-work/#the-canvas-element P3 normal --- 1 contributor ian excors ian mike mikelawther noel.gordon public-html-admin public-html-wg-issue-tracking public-html-bugzilla oldest_to_newest 42867 0 contributor 2010-11-30 01:11:46 +0000 Specification: http://www.whatwg.org/specs/web-apps/current-work/complete.html Section: http://www.whatwg.org/specs/web-apps/current-work/#the-canvas-element Comment: should mention that .toDataURL() for image/jpeg acts as if the image was composited against black Posted from: 76.102.14.57 42868 1 ian 2010-11-30 01:20:12 +0000 Actually mozilla and safari apparently don't do that, they instead unpremultiply the colours. Either way, this needs speccing. Philip, I'm told you have tests for this that may not match implementations? Can you elaborate? Specifically, this one: http://philip.html5.org/tests/canvas/suite/tests/toDataURL.jpeg.alpha.html 42886 2 excors 2010-11-30 11:16:05 +0000 The spec already says: "For image types that do not support an alpha channel, the image must be composited onto a solid black background using the source-over operator, and the resulting image must be the one used to create the data: URL." so I think it's clear on what's required (which is what that test tests). 42937 3 ian 2010-12-01 00:31:44 +0000 So it does. This doesn't seem to match what WebKit and Gecko do. Should we change the spec? 43058 4 excors 2010-12-04 23:48:47 +0000 Trying http://philip.html5.org/demos/canvas/jpeg-alpha.html with some variously old browsers: Firefox (3.6): returns (r, g, b, 1). Opera (10.60): returns (r, g, b, 1). IE9 (some not-quite-latest preview): blends with black. Safari (4.03 Win): blends with white. Chrome (8.0 Win): doesn't support JPEG. Doesn't look like there's really any convergence on one behaviour, so I'd guess the spec should define whatever seems the most sensible behaviour and then hope they converge in that direction. (I don't know what's really the most sensible behaviour, but what the spec says sounds plausible to me.) 43372 5 noel.gordon 2010-12-15 07:23:17 +0000 (In reply to comment #4) My results running http://philip.html5.org/demos/canvas/jpeg-alpha.html Firefox 3.6.12 win32 Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,59,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,59,255,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Chrome 10 dev win32 Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,61,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,61,255,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Safari 5.0.2 win32 Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,62,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,61,255,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(1,61,255,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(255,255,255,1) <-- bug composites on white Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(255,255,255,1) Opera 10.63 Win32 Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,64,253,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,64,253,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,63,252,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,63,252,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,56,244,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,56,244,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) For alpha != 0.0 results are the same neglecting rounding effects. For alpha == 0.0 composites on black (except safari, that is a safari bug). Philip, can you add your full results for IE9? 43419 6 noel.gordon 2010-12-15 23:40:10 +0000 No worries, mike computed the results for me. IE9 9.0.7930.16406 beta Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,32,127,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,6,25,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(0,32,127,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,6,25,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) 43472 7 noel.gordon 2010-12-20 07:38:59 +0000 I've posted a webkit patch to make chromium conform with the standard for review https://bugs.webkit.org/attachment.cgi?id=76964&action=prettypatch Chrome 10 dev Win32 + above patch Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,1.0); format: image/jpeg; output: rgba(0,63,255,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(1,31,127,1) Input: rgba(0,63,255,0.5); format: image/jpeg; output: rgba(1,31,127,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,6,25,1) Input: rgba(0,63,255,0.1); format: image/jpeg; output: rgba(0,6,25,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) Input: rgba(0,63,255,0.0); format: image/jpeg; output: rgba(0,0,0,1) 44199 8 ian 2011-01-11 19:38:35 +0000 EDITOR'S RESPONSE: This is an Editor's Response to your comment. If you are satisfied with this response, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. If you would like to escalate the issue to the full HTML Working Group, please add the TrackerRequest keyword to this bug, and suggest title and text for the tracker issue; or you may create a tracker issue yourself, if you are able to do so. For more details, see this document: http://dev.w3.org/html5/decision-policy/decision-policy.html Status: Rejected Change Description: no spec change Rationale: Based on the above, I'm going to reject this bug and leave it as is. Please do not hesitate to reopen it if I am mistaken in doing this. 47549 9 noel.gordon 2011-04-19 01:04:02 +0000 https://bugzilla.mozilla.org/show_bug.cgi?id=650720 53791 10 mike 2011-08-04 05:17:23 +0000 mass-move component to LC1 57499 11 noel.gordon 2011-09-29 08:16:44 +0000 Safari (webkit nightly) and Chromium Mac now conform after change http://trac.webkit.org/changeset/96000