See bug 959925 for the use case. .createImageData is unavailable from workers.

This isn't in the spec, though.

Actually it is. http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas/#hitregionoptions > [Constructor (Uint8ClampedArray data, unsigned long width, unsigned long height)] > interface ImageData { > readonly attribute unsigned long width; > readonly attribute unsigned long height; > readonly attribute Uint8ClampedArray data; > };

Oh, yet another discrepancy between WHATWG and W3C :( http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#hitregionoptions

OTOH, WHATWG's ImageData has resolution but W3C's one doesn't. I don't understand why W3C bugzilla 21045 and 21046 were closed.

I think we should do this, fwiw.

(In reply to comment #5) > I think we should do this, fwiw. Yeah, and fix the whatwg spec to add a ctor there too!

The problem is, the WHATWG spec has an attribute what the W3C spec does not. How the constructor should be? [Constructor (Uint8ClampedArray data, unsigned long width, unsigned long height, optional double resolution)]? [Constructor (ImageDataInit initDict)]? Or whatever else?

resolution's going away; the constructor as specced on the w3c side is probably ok.

Actually the W3C one's arguments don't make much sense... I'll spec something on the WHATWG side.

Done. There's two constructors: new ImageData(w, h); // returns a blank ImageData of the given dimensions new ImageData(data, w[, h]); // returns a new ImageData that references the given data, using the given width See: http://www.whatwg.org/html#dom-imagedata

ping?

Comment on attachment 8362161 [details] [diff] [review] Implement ImageData constructor >+ if (aWidth <= 0 || aHeight <= 0) { They're unsigned, so just == 0, please. >+ if (length <= 0 || length & 3) { Likewise. Also, "% 4" would be clearer than "& 3" here, I think. >+ length >>= 2; length /= 4, please. The compiler will strength-reduce as needed, and the code is clearer. >+ if (aWidth <= 0) { Again, just ==. Also, please file a spec issue; the spec doesn't do this check, but should. r=me with that

(In reply to Boris Zbarsky [:bz] from comment #14) > >+ if (aWidth <= 0) { > > Again, just ==. Also, please file a spec issue; the spec doesn't do this > check, but should. It is covered by the text "If length is not an integral multiple of sw," in the spec. If sw is zero, length will never be an integral multiple of sw. Our explicit zero check is just an implementation detail. https://hg.mozilla.org/integration/mozilla-inbound/rev/4a801fc05819

> It is covered by the text "If length is not an integral multiple of sw," in the spec. I think that assumes an unwarranted level of mathematical sophistication on the part of spec readers. The spec should just have an explicit check for 0 here before that test.

Hm, indeed I forgot the check until the test crashed despite that programmers must be careful about the zero division. Filed <https://www.w3.org/Bugs/Public/show_bug.cgi?id=24429>.

This API was implemented incorrectly. The spec says that imagedata should keep a reference to the data but it seems to create a copy.

(In reply to Hixie (not reading bugmail) from comment #9) > Actually the W3C one's arguments don't make much sense... I'll spec > something on the WHATWG side. The W3C level 2 version should just be a copy of the WhatWG. Not sure what was there before...

(In reply to Rik Cabanier from comment #19) > This API was implemented incorrectly. > The spec says that imagedata should keep a reference to the data but it > seems to create a copy. Our implementation doesn't create a copy. < var a=new Uint8ClampedArray([1,2,3,4]);var i=new ImageData(a,1);i.data.set([5,6,7,8]);a; > Uint8ClampedArray [ 5, 6, 7, 8 ] I even added an automated test to verify that. Why do you think it creates a copy? (In reply to Rik Cabanier from comment #20) > (In reply to Hixie (not reading bugmail) from comment #9) > > Actually the W3C one's arguments don't make much sense... I'll spec > > something on the WHATWG side. > > The W3C level 2 version should just be a copy of the WhatWG. Not sure what > was there before... Because I referred a wrong version on the W3C site. https://www.w3.org/Bugs/Public/show_bug.cgi?id=24298#c6

I agree with Masatoshi Kimura. The code (which is _really_ simple), and basic tests, all indicate the constructor takes a reference. Why do you think it creates a copy?

I looked at the wrong constructor. Sorry about that!

Doc updated: https://developer.mozilla.org/en-US/docs/Web/API/ImageData https://developer.mozilla.org/en-US/docs/Web/API/ImageData.ImageData https://developer.mozilla.org/en-US/Firefox/Releases/29