[PDF] Add support for Shaders.
- Shaders, or as they are referred to in PDF, patterns, are drawn in the coordinate system of the initial page, so when we canonicalize them, we have to consider the current transform and where they are constructed.
- Image shaders are tiled by default, this makes repeat and mirror modes easy, but means we have to draw a pattern as large as the current clip to support clamp mode.
- Gradient shaders are implemented with type 4 functions, which are basically small snippets of post script code. I've tried to make the code generation modular and heavily commented to make it easy to understand or expand.
Review URL: http://codereview.appspot.com/4239061
git-svn-id: http://skia.googlecode.com/svn/trunk@905 2bbb7eff-a529-9590-31e7-b0007b416f81
8 files changed