Bugzilla – Bug 19820
Description of transformation in drawimage is confusing
Last modified: 2013-02-01 07:35:43 UTC
The text for drawImage currently states:
When drawImage() is invoked, the region of the image specified by the source rectangle must be painted on the region of the canvas specified by the destination rectangle, after applying the current transformation matrix to the points of the destination rectangle.
This is a bit confusing since you don't really apply the transform to the points. Basically, you map the source rect to the destination rect and then transform the destination rectangle.
I believe the spec should also call out that there should be no loss of precision when doing this (i.e. if the destination has half the pixels but scaled by 2, the original pixel should be preserve)
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
Applying the matrix is not on the points of a rectangle. Also clarified that the original image is not updated.
Have you suggested this change to Ian?
No, I thought he was watching our bugs as well. I'd be glad to suggest it. (In reply to comment #2)
> Have you suggested this change to Ian?
Note, he made this change: