force opaque if kCGImageAlpha returns None

BUG=skia:2424
R=caryclark@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/355403003

diff --git a/src/ports/SkImageDecoder_CG.cpp b/src/ports/SkImageDecoder_CG.cpp
index 8bf30d2cc9b1ba15978fcdfd7d2f7e4631ebe00e..7bebf394da5947dba78ea65b5cb01c95bf63d5bd 100644 (file)
--- a/src/ports/SkImageDecoder_CG.cpp
+++ b/src/ports/SkImageDecoder_CG.cpp
@@ -50,6 +50,56 @@ protected:
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode);
 };
 
+static void argb_4444_force_opaque(void* row, int count) {
+    uint16_t* row16 = (uint16_t*)row;
+    for (int i = 0; i < count; ++i) {
+        row16[i] |= 0xF000;
+    }
+}
+
+static void argb_8888_force_opaque(void* row, int count) {
+    // can use RGBA or BGRA, they have the same shift for alpha
+    const uint32_t alphaMask = 0xFF << SK_RGBA_A32_SHIFT;
+    uint32_t* row32 = (uint32_t*)row;
+    for (int i = 0; i < count; ++i) {
+        row32[i] |= alphaMask;
+    }
+}
+
+static void alpha_8_force_opaque(void* row, int count) {
+    memset(row, 0xFF, count);
+}
+
+static void force_opaque(SkBitmap* bm) {
+    SkAutoLockPixels alp(*bm);
+    if (!bm->getPixels()) {
+        return;
+    }
+
+    void (*proc)(void*, int);
+    switch (bm->colorType()) {
+        case kARGB_4444_SkColorType:
+            proc = argb_4444_force_opaque;
+            break;
+        case kRGBA_8888_SkColorType:
+        case kBGRA_8888_SkColorType:
+            proc = argb_8888_force_opaque;
+            break;
+        case kAlpha_8_SkColorType:
+            proc = alpha_8_force_opaque;
+            break;
+        default:
+            return;
+    }
+
+    char* row = (char*)bm->getPixels();
+    for (int y = 0; y < bm->height(); ++y) {
+        proc(row, bm->width());
+        row += bm->rowBytes();
+    }
+    bm->setAlphaType(kOpaque_SkAlphaType);
+}
+
 #define BITMAP_INFO (kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast)
 
 bool SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
@@ -89,8 +139,10 @@ bool SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
         case kCGImageAlphaNone:
         case kCGImageAlphaNoneSkipLast:
         case kCGImageAlphaNoneSkipFirst:
-            SkASSERT(SkBitmap::ComputeIsOpaque(*bm));
-            bm->setAlphaType(kOpaque_SkAlphaType);
+            // We're opaque, but we can't rely on the data always having 0xFF
+            // in the alpha slot (which Skia wants), so we have to ram it in
+            // ourselves.
+            force_opaque(bm);
             break;
         default:
             // we don't know if we're opaque or not, so compute it.