On Jun 4, 2010, at 10:05 AM, Rob Evans wrote: > Hi, > > I wonder if this is the correct place to post this but I > cannot find any resources online as canvas is so new. Canvas isn't new -- it's at least 4 or 5 years old, and has been in the html5 spec for at least 2 or 3 of those years -- I believe the MDC has some of the best API documentation (at least in terms of providing examples of how the APIs are used.)
> > After grabbing some image data from a canvas with the > getImageData call, I cannot find a way to put the image data onto a canvas > scaled down. > > If I use the canvas scale function and then put the image > data, no scaling occurs. Is there any way to scale with putImageData? No. The ImageData API documentation is very clear on this, and has not changed substantively in a few years now. get/putImageData are not effected by the current CTM. > If not I think it would be a useful addition to the > specification. I can imagine many situations where copying a section of the > canvas and applying scaling before pasting it back to the canvas would be > useful! You shouldn't be using ImageData to do this -- CanvasRenderingContext2D.drawImage supports canvas elements, and has well defined semantics for drawing the contents of a canvas element into its own context -- in addition to supporting non-identity CTMs this is also likely quite a bit faster in the identity case than an imagedata based approach. Is there some specific reason you want to use the ImageData API? --Oliver > > Thanks, > > Rob Evans > CTO > mtn-i LTD
