This patch adds the parameter to the filterImageGPU() signature, plumbs through the code on the GPU side, and implements support for it in SkXfermodeImageFilter for both raster and GPU.
Of the remaining filters with GPU implementations, Blur, Morphology, Bicubic and Displacement work fine; they're commutative wrt offset and can simply pass it up the chain. Blend is not, but will be removed shortly anyway (has been replaced with SkXfermodeImageFilter in Blink).
R=reed@google.com, bsalomon@google.com
Author: senorblanco@chromium.org
Review URL: https://chromiumcodereview.appspot.com/15995026
git-svn-id: http://skia.googlecode.com/svn/trunk@9977 2bbb7eff-a529-9590-31e7-b0007b416f81
For the raster path, we do a straightforward 2-pass method: draw background, then composite the foreground over it.
For the GPU path, if the xfermode can be expressed as an effect, we build an effect with the background texture incorporated, then do a single-pass draw fetching both foreground and background textures, and compositing to the result. If the xfermode is expressed as src/dst coefficients, we do a 2-pass draw as in the raster path and use fixed-function blending.
R=bsalomon@google.com, reed@google.com
Review URL: https://codereview.chromium.org/16125008
git-svn-id: http://skia.googlecode.com/svn/trunk@9373 2bbb7eff-a529-9590-31e7-b0007b416f81
