ACTION-3099: Give a description of how porter-duff behaves differently from blend modes (group invariance)
Give a description of how porter-duff behaves differently from blend modes (group invariance)
- State:
- closed
- Person:
- Rik Cabanier
- Due on:
- August 5, 2011
- Created on:
- July 29, 2011
- Associated Product:
- Module: Compositing
- Related emails:
- minutes, SVG WG Seattle F2F 2011 day 3 (from cam@mcc.id.au on 2011-07-29)
Related notes:
P-D is compositing which is very different from blending.
Blending takes the source image, calculates the background (based on the formulas in the filters/svg compositing spec) and produces a new image that is based on the blending formula select.
This resulting image is then composited with the select p-d mode (which is src-over by default.
Compositing always works on 2 images, ie
<rect id=1>
<g>
<rect id=2>
<rect id=3>
the composting will happen as follows:
1. create image for rect 1. there are no sibling so don't composite
2. create image for rect 2. there are no sibling so don't composite
3. create image for rect 3. composite with rect2
4. process the g. composite result of step 1 with the result of step 3
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