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Diffstat (limited to 'docs/rendering-parity-design.md')
| -rw-r--r-- | docs/rendering-parity-design.md | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/docs/rendering-parity-design.md b/docs/rendering-parity-design.md index b6036543..14a5bc62 100644 --- a/docs/rendering-parity-design.md +++ b/docs/rendering-parity-design.md @@ -76,8 +76,10 @@ out.rgb = p * a * c + (1 - a) * dst.rgb out.a = p * a + (1 - a) * dst.a ``` -Thus PDF text is part of a raster page and fades with the page; native text does -not. Transparent image pixels preserve the destination. Ordinary source-over +This describes ordinary image attachments and the existing SDL PDF path. +macOS PDFs now separate unpainted paper from content: paper uses p and content +uses its own coverage, without multiplying that coverage by p. A future shared +scene must carry this paper/content distinction explicitly. Transparent image pixels preserve the destination. Ordinary source-over with source alpha p*a is not equivalent. Any future operation API needs to express this distinction directly and specify sampling and premultiplication. |