commit e8354b276a25ad7c004f3f5d208d6c93e8f2fa06
author Mike Klein <mtklein@google.com> Fri Nov 02 14:23:45 2018 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Fri Nov 02 19:28:57 2018 +0000
tree c12eedaecb958f8e0418da9eb5149dabd3826d82
parent ab350ca7302303b4e05320453b39636c0a4219b6

DeMorgan's blend-on-black logic

I kept reading and re-reading the existing logic and couldn't figure it
out until I looked at the AlphaOption enum.  I think this direction
reads a bit more clearly.

(This is why we have those ->premul methods.  Oddly, we fail for 4444.)

Change-Id: I74ea2e380d5ab9526ea1e6412929346ad9c0ead6
Reviewed-on: https://skia-review.googlesource.com/c/167921
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

src/images/SkJpegEncoder.cpp

diff --git a/src/images/SkJpegEncoder.cpp b/src/images/SkJpegEncoder.cpp
index d6828b4..37a4911 100644
--- a/src/images/SkJpegEncoder.cpp
+++ b/src/images/SkJpegEncoder.cpp
@@ -68,13 +68,11 @@
 bool SkJpegEncoderMgr::setParams(const SkImageInfo& srcInfo, const SkJpegEncoder::Options& options)
 {
     auto chooseProc8888 = [&]() {
-        if (kUnpremul_SkAlphaType != srcInfo.alphaType() ||
-            SkJpegEncoder::AlphaOption::kIgnore == options.fAlphaOption)
-        {
-            return (transform_scanline_proc) nullptr;
+        if (kUnpremul_SkAlphaType == srcInfo.alphaType() &&
+                options.fAlphaOption == SkJpegEncoder::AlphaOption::kBlendOnBlack) {
+            return transform_scanline_to_premul_legacy;
         }
-
-        return transform_scanline_to_premul_legacy;
+        return (transform_scanline_proc) nullptr;
     };
 
     J_COLOR_SPACE jpegColorType = JCS_EXT_RGBA;
@@ -110,12 +108,11 @@
             numComponents = 1;
             break;
         case kRGBA_F16_SkColorType:
-            if (kUnpremul_SkAlphaType != srcInfo.alphaType() ||
-                SkJpegEncoder::AlphaOption::kIgnore == options.fAlphaOption)
-            {
-                fProc = transform_scanline_F16_to_8888;
-            } else {
+            if (kUnpremul_SkAlphaType == srcInfo.alphaType() &&
+                    options.fAlphaOption == SkJpegEncoder::AlphaOption::kBlendOnBlack) {
                 fProc = transform_scanline_F16_to_premul_8888;
+            } else {
+                fProc = transform_scanline_F16_to_8888;
             }
             jpegColorType = JCS_EXT_RGBA;
             numComponents = 4;