SkScaledCodec class

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 84e90d444249142d69a68cd52cab59cebb37c30a..9a91caffdd35ea235d7894ee1d14ec9c311da15b 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -11,6 +11,7 @@
 #include "SkJpegUtility_codec.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
+#include "SkScaledCodec.h"
 #include "SkScanlineDecoder.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
@@ -189,6 +190,43 @@ SkISize SkJpegCodec::onGetScaledDimensions(float desiredScale) const {
     return SkISize::Make(dinfo.output_width, dinfo.output_height);
 }
 
+// The swizzler is only used for sampling in the x direction
+// when sampling a scanlineDecoder is used. The swizzler is not used in onGetPixels
+SkCodec::Result SkJpegCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
+                                               void* dst, size_t rowBytes,
+                                               const Options& options,
+                                               SkPMColor ctable[],
+                                               int* ctableCount) {
+
+    const SkColorType srcColorType = requestedInfo.colorType();
+    SkSwizzler::SrcConfig srcConfig;
+    switch (srcColorType) {
+        case kGray_8_SkColorType:
+            srcConfig = SkSwizzler::kGray;
+            break;
+        case kRGBA_8888_SkColorType:
+            srcConfig = SkSwizzler::kRGBX;
+            break;
+        case kBGRA_8888_SkColorType:
+            srcConfig = SkSwizzler::kBGRX;
+            break;
+        case kRGB_565_SkColorType:
+            srcConfig = SkSwizzler::kRGB_565;
+            break;
+        default:
+            //would have exited before now if the colorType was supported by jpeg
+            SkASSERT(false);
+    }
+
+    fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, NULL, requestedInfo,
+                                               options.fZeroInitialized, this->getInfo().width()));
+    if (!fSwizzler) {
+        // FIXME: CreateSwizzler could fail for another reason.
+        return kUnimplemented;
+    }
+    return kSuccess;
+}
+
 /*
  * Handles rewinding the input stream if it is necessary
  */
@@ -272,10 +310,10 @@ bool SkJpegCodec::setOutputColorSpace(const SkImageInfo& dst) {
 }
 
 /*
- * Checks if we can scale to the requested dimensions and scales the dimensions
- * if possible
+ * Checks if we can natively scale to the requested dimensions and natively scales the 
+ * dimensions if possible
  */
-bool SkJpegCodec::scaleToDimensions(uint32_t dstWidth, uint32_t dstHeight) {
+bool SkJpegCodec::nativelyScaleToDimensions(uint32_t dstWidth, uint32_t dstHeight) {
     // libjpeg-turbo can scale to 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8, and 1/1
     fDecoderMgr->dinfo()->scale_denom = 8;
     fDecoderMgr->dinfo()->scale_num = 8;
@@ -287,7 +325,10 @@ bool SkJpegCodec::scaleToDimensions(uint32_t dstWidth, uint32_t dstHeight) {
         if (1 == fDecoderMgr->dinfo()->scale_num ||
                 dstWidth > fDecoderMgr->dinfo()->output_width ||
                 dstHeight > fDecoderMgr->dinfo()->output_height) {
-            return fDecoderMgr->returnFalse("could not scale to requested dimensions");
+            // reset native scale settings on failure because this may be supported by the swizzler 
+            this->fDecoderMgr->dinfo()->scale_num = 8;
+            turbo_jpeg_calc_output_dimensions(this->fDecoderMgr->dinfo());
+            return false;
         }
 
         // Try the next scale
@@ -327,7 +368,7 @@ SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
     }
 
     // Perform the necessary scaling
-    if (!this->scaleToDimensions(dstInfo.width(), dstInfo.height())) {
+    if (!this->nativelyScaleToDimensions(dstInfo.width(), dstInfo.height())) {
         return fDecoderMgr->returnFailure("cannot scale to requested dims", kInvalidScale);
     }
 
@@ -394,7 +435,12 @@ public:
         : INHERITED(dstInfo)
         , fCodec(codec)
         , fOpts(opts)
-    {}
+    {
+        if(fCodec->fSwizzler) {
+            fStorage.reset(fCodec->getInfo().width() * dstInfo.minRowBytes());

[scroggo, 2015/08/03 19:16:20]

This seems like more than we need to allocate. (Maybe this is why it was such a
large part of the slowdown?)

In SkPngScanlineDecoder we set this to <src width> * <src bytes per pixel>.

I assume it should be the same here? Instead, we are multiplying <src width> *
<dst width> * <dst bytes per pixel>

[emmaleer, 2015/08/04 18:56:53]

Acknowledged.

+            fSrcRow = static_cast<uint8_t*>(fStorage.get());
+        }

[scroggo, 2015/08/03 19:16:20]

else {
  fSrcRow = NULL;
}

[emmaleer, 2015/08/04 18:56:53]

Acknowledged.

+    }
 
     virtual ~SkJpegScanlineDecoder() {
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
@@ -413,9 +459,16 @@ public:
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
             return fCodec->fDecoderMgr->returnFailure("setjmp", SkCodec::kInvalidInput);
         }
-
         // Read rows one at a time
-        JSAMPLE* dstRow = (JSAMPLE*) dst;
+        JSAMPLE* dstRow;
+        if (fCodec->fSwizzler) {
+            // write data to storage row, then sample using swizzler         
+            dstRow = fSrcRow;
+        } else {
+            // write data directly to dst
+            dstRow = (JSAMPLE*) dst;
+        }
+
         for (int y = 0; y < count; y++) {
             // Read row of the image
             uint32_t rowsDecoded =
@@ -435,10 +488,14 @@ public:
                 convert_CMYK_to_RGBA(dstRow, this->dstInfo().width());
             }
 
-            // Move to the next row
-            dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
+            if(fCodec->fSwizzler) {
+                // use swizzler to sample row
+                fCodec->fSwizzler->swizzle(dst, dstRow);
+                dst = SkTAddOffset<JSAMPLE>(dst, rowBytes);
+            } else {
+                dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
+            }
         }
-
         return SkCodec::kSuccess;
     }
 
@@ -464,6 +521,8 @@ public:
 
 private:
     SkAutoTDelete<SkJpegCodec> fCodec;
+    SkAutoMalloc               fStorage;    // Only used if sampling is needed
+    uint8_t*                   fSrcRow;     // Only used if sampling is needed
     const SkCodec::Options&    fOpts;
 
     typedef SkScanlineDecoder INHERITED;
@@ -500,9 +559,18 @@ SkScanlineDecoder* SkJpegCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
     }
 
     // Perform the necessary scaling
-    if (!codec->scaleToDimensions(dstInfo.width(), dstInfo.height())) {
-        SkCodecPrintf("Cannot scale to output dimensions\n");
-        return NULL;
+    if (!codec->nativelyScaleToDimensions(dstInfo.width(), dstInfo.height())) {
+        // native scaling to dstInfo dimensions not supported
+
+        if (!SkScaledCodec::DimensionsSupportedForSampling(this->getInfo(), dstInfo)) {
+            return NULL;
+        }
+        // create swizzler for sampling
+        if (codec->initializeSwizzler(dstInfo, NULL, dstInfo.minRowBytes(), options, ctable,
+                                      ctableCount) != kSuccess) {
+            SkCodecPrintf("failed to initialize the swizzler.\n");
+            return NULL;
+        }
     }
 
     // Now, given valid output dimensions, we can start the decompress