Make SkSwizzler::Fill() support 565

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 5acc0b396c54d34abb922f80687104b54f85990a..84e90d444249142d69a68cd52cab59cebb37c30a 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -354,7 +354,14 @@ SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
             // the fill color for opaque images.  If the destination is kGray,
             // the low 8 bits of SK_ColorBLACK will be used.  Conveniently,
             // these are zeros, which is the representation for black in kGray.
-            SkSwizzler::Fill(dstRow, dstInfo, dstRowBytes, dstHeight - y, SK_ColorBLACK, NULL);
+            // If the destination is kRGB_565, the low 16 bits of SK_ColorBLACK
+            // will be used.  Conveniently, these are zeros, which is the
+            // representation for black in kRGB_565.
+            if (kNo_ZeroInitialized == options.fZeroInitialized ||
+                    kN32_SkColorType == dstInfo.colorType()) {
+                SkSwizzler::Fill(dstRow, dstInfo, dstRowBytes, dstHeight - y,
+                        SK_ColorBLACK, NULL);
+            }
 
             // Prevent libjpeg from failing on incomplete decode
             dinfo->output_scanline = dstHeight;
@@ -382,9 +389,11 @@ SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
  */
 class SkJpegScanlineDecoder : public SkScanlineDecoder {
 public:
-    SkJpegScanlineDecoder(const SkImageInfo& dstInfo, SkJpegCodec* codec)
+    SkJpegScanlineDecoder(const SkImageInfo& dstInfo, SkJpegCodec* codec,
+            const SkCodec::Options& opts)
         : INHERITED(dstInfo)
         , fCodec(codec)
+        , fOpts(opts)
     {}
 
     virtual ~SkJpegScanlineDecoder() {
@@ -412,8 +421,11 @@ public:
             uint32_t rowsDecoded =
                     turbo_jpeg_read_scanlines(fCodec->fDecoderMgr->dinfo(), &dstRow, 1);
             if (rowsDecoded != 1) {
-                SkSwizzler::Fill(
-                        dstRow, this->dstInfo(), rowBytes, count - y, SK_ColorBLACK, NULL);
+                if (SkCodec::kNo_ZeroInitialized == fOpts.fZeroInitialized ||
+                        kN32_SkColorType == this->dstInfo().colorType()) {
+                    SkSwizzler::Fill(dstRow, this->dstInfo(), rowBytes,
+                            count - y, SK_ColorBLACK, NULL);
+                }
                 fCodec->fDecoderMgr->dinfo()->output_scanline = this->dstInfo().height();
                 return SkCodec::kIncompleteInput;
             }
@@ -452,6 +464,7 @@ public:
 
 private:
     SkAutoTDelete<SkJpegCodec> fCodec;
+    const SkCodec::Options&    fOpts;

[scroggo, 2015/08/03 18:41:24]

I missed this when I first reviewed, but mention it in
https://codereview.chromium.org/1267583002/ (which also fixes it) - making this
a reference is not a good idea. We do not know the lifetime of the object passed
in, so we cannot be sure that the Options object we are referring to will still
exist when we need it.

We actually *do* know of an example when this does not work - if the client
called getScanlineDecoder with a NULL Options object, getScanlineDecoder puts
one on the stack and passes it to onGetScanlineDecoder. So as soon as the client
receives the JpegScanlineDecoder, the object they have is no longer valid.

 
     typedef SkScanlineDecoder INHERITED;
 };
@@ -499,5 +512,5 @@ SkScanlineDecoder* SkJpegCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
     }
 
     // Return the new scanline decoder
-    return SkNEW_ARGS(SkJpegScanlineDecoder, (dstInfo, codec.detach()));
+    return SkNEW_ARGS(SkJpegScanlineDecoder, (dstInfo, codec.detach(), options));
 }