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..6012978c38ea27833a29e6333f31bff8d181a91b 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, options.fSampleX));
     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 +634,11 @@ public:
 
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
+    bool onIsInterlaced() override {
+        return false;
+    }
+    
+
 private:
     SkAutoTDelete<SkPngCodec>   fCodec;
     bool                        fHasAlpha;
@@ -653,7 +658,7 @@ 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 +713,10 @@ public:
 
     bool onReallyHasAlpha() const override { return fHasAlpha; }
 
+    bool onIsInterlaced() override {
+        return true; 
+    }
+
 private:
     SkAutoTDelete<SkPngCodec>   fCodec;
     bool                        fHasAlpha;
@@ -728,8 +737,23 @@ SkScanlineDecoder* SkPngCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
         return NULL;
     }
     // Check to see if scaling was requested.
-    if (dstInfo.dimensions() != this->getInfo().dimensions()) {
-        return NULL;
+    if(options.fSampleX == 1) {

[scroggo, 2015/07/28 15:58:10]

It would be nice to be able to share this code with other decoders somehow.

+        // the caller is not sampling, dimensions must be equal
+        if (dstInfo.dimensions() != this->getInfo().dimensions()) {
+            return NULL;
+        }
+
+    } else {
+        // the caller is sampling
+        // heights must be equal as SkCodec_libpng has no native y sampling
+        if (dstInfo.height() != this->getInfo().height()) {
+            return NULL;
+        }
+        // dstWidth must be srcWidth / sampleX
+        if (dstInfo.width() != this->getInfo().width() / options.fSampleX) {
+            return NULL;
+        }
+
     }
     // Create a new SkPngCodec, to be owned by the scanline decoder.
     SkStream* stream = this->stream()->duplicate();