onGetScanlines and onSkipScanlines for interlaced pngs

dm/DMSrcSink.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "DMSrcSink.h"
 #include "SamplePipeControllers.h"
 #include "SkCodec.h"
@@ skipping 122 matching lines @@
         decodeInfo = decodeInfo.makeAlphaType(kPremul_SkAlphaType);
     }
 
     SkBitmap bitmap;
     if (!bitmap.tryAllocPixels(decodeInfo, NULL, colorTable.get())) {
         return SkStringPrintf("Image(%s) is too large (%d x %d)\n", fPath.c_str(),
                               decodeInfo.width(), decodeInfo.height());
     }
 
     switch (fMode) {
-        case kNormal_Mode:
+        case kNormal_Mode: {
             switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), NULL,
                     colorPtr, colorCountPtr)) {
                 case SkImageGenerator::kSuccess:
                     // We consider incomplete to be valid, since we should still decode what is
                     // available.
                 case SkImageGenerator::kIncompleteInput:
                     break;
                 case SkImageGenerator::kInvalidConversion:
                     return Error::Nonfatal("Incompatible colortype conversion");
                 default:
                     // Everything else is considered a failure.
                     return SkStringPrintf("Couldn't getPixels %s.", fPath.c_str());
             }
             canvas->drawBitmap(bitmap, 0, 0);
             break;
+        }
         case kScanline_Mode: {
             SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(decodeInfo, NULL,
                     colorPtr, colorCountPtr);
             if (NULL == scanlineDecoder) {
                 return Error::Nonfatal("Cannot use scanline decoder for all images");
             }
-            for (int y = 0; y < decodeInfo.height(); ++y) {
-                const SkImageGenerator::Result result = scanlineDecoder->getScanlines(
-                        bitmap.getAddr(0, y), 1, 0);
-                switch (result) {
-                    case SkImageGenerator::kSuccess:
-                    case SkImageGenerator::kIncompleteInput:
-                        break;
-                    default:
-                        return SkStringPrintf("%s failed after %d scanlines with error message %d",
-                                              fPath.c_str(), y-1, (int) result);
-                }
+            const SkImageGenerator::Result result = scanlineDecoder->getScanlines(
+                    bitmap.getAddr(0, 0), decodeInfo.height(), bitmap.rowBytes());
+            switch (result) {
+                case SkImageGenerator::kSuccess:
+                case SkImageGenerator::kIncompleteInput:
+                    break;
+                default:
+                    return SkStringPrintf("%s failed with error message %d",
+                                          fPath.c_str(), (int) result);
             }
             canvas->drawBitmap(bitmap, 0, 0);
             break;
         }
         case kScanline_Subset_Mode: {
             //this mode decodes the image in divisor*divisor subsets, using a scanline decoder
             const int divisor = 2;
             const int w = decodeInfo.width();
             const int h = decodeInfo.height();
             if (w*h == 1) {
@@ skipping 17 matching lines @@
             * subsetBm's size is determined based on the current subset and may be larger for end
             * subsets.
             */
             SkImageInfo largestSubsetDecodeInfo =
                     decodeInfo.makeWH(subsetWidth + extraX, subsetHeight + extraY);
             SkBitmap largestSubsetBm;
             if (!largestSubsetBm.tryAllocPixels(largestSubsetDecodeInfo, NULL, colorTable.get())) {
                 return SkStringPrintf("Image(%s) is too large (%d x %d)\n", fPath.c_str(),
                         largestSubsetDecodeInfo.width(), largestSubsetDecodeInfo.height());
             }
-            char* line = SkNEW_ARRAY(char, decodeInfo.minRowBytes());
-            SkAutoTDeleteArray<char> lineDeleter(line);
+            const size_t rowBytes = decodeInfo.minRowBytes();
+            char* buffer = SkNEW_ARRAY(char, largestSubsetDecodeInfo.height() * rowBytes);
+            SkAutoTDeleteArray<char> lineDeleter(buffer);
             for (int col = 0; col < divisor; col++) {
                 //currentSubsetWidth may be larger than subsetWidth for rightmost subsets
                 const int currentSubsetWidth = (col + 1 == divisor) ?
                         subsetWidth + extraX : subsetWidth;
                 const int x = col * subsetWidth;
                 for (int row = 0; row < divisor; row++) {
                     //currentSubsetHeight may be larger than subsetHeight for bottom subsets
                     const int currentSubsetHeight = (row + 1 == divisor) ?
                             subsetHeight + extraY : subsetHeight;
                     const int y = row * subsetHeight;
@@ skipping 18 matching lines @@
                         default:
                             return SkStringPrintf("%s failed after attempting to skip %d scanlines"
                                     "with error message %d", fPath.c_str(), y, (int) skipResult);
                     }
                     //create and set size of subsetBm
                     SkBitmap subsetBm;
                     SkIRect bounds = SkIRect::MakeWH(subsetWidth, subsetHeight);
                     bounds.setXYWH(0, 0, currentSubsetWidth, currentSubsetHeight);
                     SkAssertResult(largestSubsetBm.extractSubset(&subsetBm, bounds));
                     SkAutoLockPixels autlockSubsetBm(subsetBm, true);
+                    const SkImageGenerator::Result subsetResult =
+                        subsetScanlineDecoder->getScanlines(buffer, currentSubsetHeight, rowBytes);
+                    switch (subsetResult) {
+                        case SkImageGenerator::kSuccess:
+                        case SkImageGenerator::kIncompleteInput:
+                            break;
+                        default:
+                            return SkStringPrintf("%s failed with error message %d", 
+                                    fPath.c_str(), (int) subsetResult);
+                    }
+                    const size_t bpp = decodeInfo.bytesPerPixel();
+                    /*    
+                     * we copy all the lines at once becuase when calling getScanlines for 
+                     * interlaced pngs the entire image must be read regardless of the number 
+                     * of lines requested.  Reading an interlaced png in a loop, line-by-line, would
+                     * decode the entire image height times, which is very slow
+                     * it is aknowledged that copying each line as you read it in a loop
+                     * may be faster for other types of images.  Since this is a correctness test
+                     * that's okay.
+                    */
+                    char* bufferRow = buffer; 
                     for (int subsetY = 0; subsetY < currentSubsetHeight; ++subsetY) {
-                        const SkImageGenerator::Result subsetResult =
-                                subsetScanlineDecoder->getScanlines(line, 1, 0);
-                        const size_t bpp = decodeInfo.bytesPerPixel();
-                        //copy section of line based on x value
-                        memcpy(subsetBm.getAddr(0, subsetY), line + x*bpp, currentSubsetWidth*bpp);
-                        switch (subsetResult) {
-                            case SkImageGenerator::kSuccess:
-                            case SkImageGenerator::kIncompleteInput:
-                                break;
-                            default:
-                                return SkStringPrintf("%s failed after %d scanlines with error" 
-                                        "message %d", fPath.c_str(), y-1, (int) subsetResult);
-                        }
+                        memcpy(subsetBm.getAddr(0, subsetY), bufferRow + x*bpp, 
+                                currentSubsetWidth*bpp);
+                        bufferRow += rowBytes;
                     }
+                    
                     canvas->drawBitmap(subsetBm, SkIntToScalar(x), SkIntToScalar(y));
                 }
             }
             break;
         }
         case kStripe_Mode: {
             const int height = decodeInfo.height();
             // This value is chosen arbitrarily.  We exercise more cases by choosing a value that
             // does not align with image blocks.
             const int stripeHeight = 37;
@@ skipping 59 matching lines @@
                     switch (result) {
                         case SkImageGenerator::kSuccess:
                         case SkImageGenerator::kIncompleteInput:
                             break;
                         default:
                             return SkStringPrintf("Cannot skip scanlines for %s.", fPath.c_str());
                     }
                 }
             }
             canvas->drawBitmap(bitmap, 0, 0);
+            break;
         }
     }
     return "";
 }
 
 SkISize CodecSrc::size() const {
     SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(fPath.c_str()));
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(encoded));
     if (NULL != codec) {
         SkISize size = codec->getScaledDimensions(fScale);
@@ skipping 613 matching lines @@
             skr.visit<void>(i, drawsAsSingletonPictures);
         }
         SkAutoTUnref<SkPicture> macroPic(macroRec.endRecordingAsPicture());
 
         canvas->drawPicture(macroPic);
         return "";
     });
 }
 
 }  // namespace DM