- From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
- Date: Sat, 21 Aug 2010 17:54:45 +1000
Hi all, I've tried to work with the globalCompositeOperation [1] over the last days for a particular use case where I am trying to use a gradient to merge with a canvas as a mask. I now wonder if the globalCompositeOperation is indeed meant to be used this way and what transparency means. For example, "source-in" is defined as: "A in B": Display the source image wherever both the source image and destination image are opaque. Display transparency elsewhere. What about partial transparency? I would expect the use of the canvas bitmap B as a mask for the object or image A, where A becomes partially transparent where-ever B is partially transparent. As it stands, browsers do not implement it this way - only completely transparent pixels will create transparency in A, which means when using a gradient that nothing become partially transparent - it's either there or gone. Should partial transparency in B not be dealt with as partial transparency in the resulting display, too? Apologies if this has been dealt with before. I'm looking at it with video as the input medium, i.e. through drawImage(), trying to make it partially transparent. Cheers, Silvia. [1] http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-globalcompositeoperation -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/attachments/20100821/1612c9bc/attachment.htm>
Received on Saturday, 21 August 2010 00:54:45 UTC