SkScaledCodec class

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 5acc0b396c54d34abb922f80687104b54f85990a..ea2834297ca77f3c484d9e0e263d1385549541a3 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -189,6 +189,41 @@ SkISize SkJpegCodec::onGetScaledDimensions(float desiredScale) const {
     return SkISize::Make(dinfo.output_width, dinfo.output_height);
 }
 
+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, dst, rowBytes,
+                                               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
  */
@@ -287,6 +322,9 @@ 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) {
+            // reset scale settings on failure 
+            this->fDecoderMgr->dinfo()->scale_num = 8;
+            turbo_jpeg_calc_output_dimensions(this->fDecoderMgr->dinfo());
             return fDecoderMgr->returnFalse("could not scale to requested dimensions");
         }
 
@@ -385,7 +423,12 @@ public:
     SkJpegScanlineDecoder(const SkImageInfo& dstInfo, SkJpegCodec* codec)
         : INHERITED(dstInfo)
         , fCodec(codec)
-    {}
+    {
+        if(fCodec->fSwizzler) {
+            fStorage.reset(fCodec->getInfo().width() * dstInfo.minRowBytes());
+            fSrcRow = static_cast<uint8_t*>(fStorage.get());
+        }
+    }
 
     virtual ~SkJpegScanlineDecoder() {
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
@@ -404,9 +447,16 @@ 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 =
@@ -423,10 +473,15 @@ 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->setDstRow(dst);
+                fCodec->fSwizzler->next(dstRow);
+                dst = SkTAddOffset<JSAMPLE>(dst, rowBytes);
+            } else {
+                dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
+            }
         }
-
         return SkCodec::kSuccess;
     }
 
@@ -452,6 +507,8 @@ public:
 
 private:
     SkAutoTDelete<SkJpegCodec> fCodec;
+    SkAutoMalloc               fStorage;

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

This one is only needed for sampling, too, right?

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

Yep! I've added a comment.

+    uint8_t*                   fSrcRow;     // Only used if sampling is needed
 
     typedef SkScanlineDecoder INHERITED;
 };
@@ -488,8 +545,22 @@ 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;
+        // native scaling to dstInfo dimensions not supported
+
+        if (dstInfo.height() != this->getInfo().height()) {

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

This should call DimensionsSupportedForSampling

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

Acknowledged.

+            // no non-native height sampling supported
+            return NULL;
+        }
+        // only support down sampling, dstWidth cannot be larger that srcWidth
+        if(dstInfo.width() > this->getInfo().width()) {
+            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