SkScaledCodec class

src/codec/SkCodec_libpng.cpp

Index: src/codec/SkCodec_libpng.cpp
diff --git a/src/codec/SkCodec_libpng.cpp b/src/codec/SkCodec_libpng.cpp
index 553233de12117ea8ccebcdfd261a720b8e721412..8169cf5bafcaa2dffe1b2384bd47e151971c683c 100644
--- a/src/codec/SkCodec_libpng.cpp
+++ b/src/codec/SkCodec_libpng.cpp
@@ -474,7 +474,7 @@ SkCodec::Result SkPngCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
     // Create the swizzler.  SkPngCodec retains ownership of the color table.
     const SkPMColor* colors = fColorTable ? fColorTable->readColors() : NULL;
     fSwizzler.reset(SkSwizzler::CreateSwizzler(fSrcConfig, colors, requestedInfo,
-            dst, rowBytes, options.fZeroInitialized));
+            dst, rowBytes, options.fZeroInitialized, this->getInfo().width()));
     if (!fSwizzler) {
         // FIXME: CreateSwizzler could fail for another reason.
         return kUnimplemented;
@@ -597,7 +597,7 @@ public:
         , fCodec(codec)
         , fHasAlpha(false)
     {
-        fStorage.reset(dstInfo.width() * SkSwizzler::BytesPerPixel(fCodec->fSrcConfig));
+        fStorage.reset(fCodec->getInfo().width() * SkSwizzler::BytesPerPixel(fCodec->fSrcConfig));
         fSrcRow = static_cast<uint8_t*>(fStorage.get());
     }
 
@@ -634,6 +634,10 @@ public:
 
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
+    bool onIsHardToSample() override {
+        return false;
+    }
+
 private:
     SkAutoTDelete<SkPngCodec>   fCodec;
     bool                        fHasAlpha;
@@ -653,7 +657,7 @@ public:
         , fCurrentRow(0)
         , fHeight(dstInfo.height())
     {
-        fSrcRowBytes = dstInfo.width() * SkSwizzler::BytesPerPixel(fCodec->fSrcConfig);
+        fSrcRowBytes = codec->getInfo().width() * SkSwizzler::BytesPerPixel(fCodec->fSrcConfig);
         fGarbageRow.reset(fSrcRowBytes);
         fGarbageRowPtr = static_cast<uint8_t*>(fGarbageRow.get());
     }
@@ -708,6 +712,10 @@ public:
 
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
+    bool onIsHardToSample() override {
+        return true;
+    }
+
 private:
     SkAutoTDelete<SkPngCodec>   fCodec;
     bool                        fHasAlpha;
@@ -728,8 +736,16 @@ SkScanlineDecoder* SkPngCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
         return NULL;
     }
     // Check to see if scaling was requested.
-    if (dstInfo.dimensions() != this->getInfo().dimensions()) {
-        return NULL;
+    if(dstInfo.dimensions() != this->getInfo().dimensions()) {
+        // the caller is sampling
+        // heights must be equal as SkCodec_libpng has no native y sampling
+        if (dstInfo.height() != this->getInfo().height()) {

[scroggo, 2015/07/31 13:35:33]

Maybe this should be another static method on SkScaledCodec, something like:

bool DimensionsSupportedForSampling(srcInfo, dstInfo);

[emmaleer, 2015/07/31 18:41:56]

Acknowledged.

+            return NULL;
+        }
+        // only support down sampling, dstWidth cannot be larger that srcWidth
+        if(dstInfo.width() > this->getInfo().width()) {
+            return NULL;
+        }
     }
     // Create a new SkPngCodec, to be owned by the scanline decoder.
     SkStream* stream = this->stream()->duplicate();