encode kAlpha_8 as grayalpha with sigbits for gray==1

Bug: skia:
Change-Id: Ib61e8e0f62af92d8746f5e73469002e7804a8447
Reviewed-on: https://skia-review.googlesource.com/78481
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/codec/SkSwizzler.cpp b/src/codec/SkSwizzler.cpp
index 84bb09702b..f3d97af3d8 100644
--- a/src/codec/SkSwizzler.cpp
+++ b/src/codec/SkSwizzler.cpp
@@ -357,6 +357,16 @@ static void fast_swizzle_grayalpha_to_n32_premul(
     SkOpts::grayA_to_rgbA((uint32_t*) dst, src + offset, width);
 }
 
+static void swizzle_grayalpha_to_a8(void* dst, const uint8_t* src, int width, int bpp,
+                                    int deltaSrc, int offset, const SkPMColor[]) {
+    src += offset;
+    uint8_t* dst8 = (uint8_t*)dst;
+    for (int x = 0; x < width; ++x) {
+        dst8[x] = src[1];   // src[0] is gray, ignored
+        src += deltaSrc;
+    }
+}
+
 // kBGR
 
 static void swizzle_bgr_to_565(
@@ -906,6 +916,9 @@ SkSwizzler* SkSwizzler::CreateSwizzler(const SkEncodedInfo& encodedInfo,
                             }
                         }
                         break;
+                    case kAlpha_8_SkColorType:
+                        proc = &swizzle_grayalpha_to_a8;
+                        break;
                     default:
                         return nullptr;
                 }