Add subsetting to SkScanlineDecoder

This CL allows the SkScanlineDecoder to decode partial
scanlines.

This is a first step in efficiently implementing subsetting
in SkScaledCodec.

BUG=skia:4209

Review URL: https://codereview.chromium.org/1390213002

3 files changed, 48 insertions, 131 deletions

diff --git a/bench/subset/SubsetSingleBench.cpp b/bench/subset/SubsetSingleBench.cpp
index b4e92e4e22..47a897fd83 100644
--- a/bench/subset/SubsetSingleBench.cpp
+++ b/bench/subset/SubsetSingleBench.cpp
@@ -65,56 +65,29 @@ void SubsetSingleBench::onDraw(int n, SkCanvas* canvas) {
     if (fUseCodec) {
         for (int count = 0; count < n; count++) {
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
+            SkASSERT(SkCodec::kOutOfOrder_SkScanlineOrder != codec->getScanlineOrder());
             const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
 
+            // The scanline decoder will handle subsetting in the x-dimension.
+            SkIRect subset = SkIRect::MakeXYWH(fOffsetLeft, 0, fSubsetWidth,
+                    codec->getInfo().height());
+            SkCodec::Options options;
+            options.fSubset = &subset;
+
             SkDEBUGCODE(SkCodec::Result result =)
-            codec->startScanlineDecode(info, nullptr, colors, &colorCount);
+            codec->startScanlineDecode(info, &options, colors, &colorCount);
             SkASSERT(result == SkCodec::kSuccess);
 
             SkBitmap bitmap;
             SkImageInfo subsetInfo = info.makeWH(fSubsetWidth, fSubsetHeight);
             alloc_pixels(&bitmap, subsetInfo, colors, colorCount);
 
-            SkDEBUGCODE(int lines = ) codec->skipScanlines(fOffsetTop);
-            SkASSERT((uint32_t) lines == fOffsetTop);
-
-            const uint32_t bpp = info.bytesPerPixel();
-
-            switch (codec->getScanlineOrder()) {
-                case SkCodec::kTopDown_SkScanlineOrder: {
-                    SkAutoTDeleteArray<uint8_t> row(new uint8_t[info.minRowBytes()]);
-                    for (uint32_t y = 0; y < fSubsetHeight; y++) {
-                        SkDEBUGCODE(lines = ) codec->getScanlines(row.get(), 1, 0);
-                        SkASSERT(lines == 1);
-
-                        memcpy(bitmap.getAddr(0, y), row.get() + fOffsetLeft * bpp,
-                                fSubsetWidth * bpp);
-                    }
-                    break;
-                }
-                case SkCodec::kNone_SkScanlineOrder: {
-                    // decode all scanlines that intersect the subset, and copy the subset
-                    // into the output.
-                    SkImageInfo stripeInfo = info.makeWH(info.width(), fSubsetHeight);
-                    SkBitmap stripeBm;
-                    alloc_pixels(&stripeBm, stripeInfo, colors, colorCount);
-
-                    SkDEBUGCODE(lines = ) codec->getScanlines(stripeBm.getPixels(), fSubsetHeight,
-                                                               stripeBm.rowBytes());
-                    SkASSERT((uint32_t) lines == fSubsetHeight);
-
-                    for (uint32_t y = 0; y < fSubsetHeight; y++) {
-                        memcpy(bitmap.getAddr(0, y), stripeBm.getAddr(fOffsetLeft, y),
-                                fSubsetWidth * bpp);
-                    }
-                    break;
-                }
-                default:
-                    // We currently are only testing kTopDown and kNone, which are the only
-                    // two used by the subsets we care about. skbug.com/4428
-                    SkASSERT(false);
+            SkDEBUGCODE(bool success = ) codec->skipScanlines(fOffsetTop);
+            SkASSERT(success);
 
-            }
+            SkDEBUGCODE(uint32_t lines = ) codec->getScanlines(bitmap.getPixels(), fSubsetHeight,
+                    bitmap.rowBytes());
+            SkASSERT(lines == fSubsetHeight);
         }
     } else {
         for (int count = 0; count < n; count++) {
diff --git a/bench/subset/SubsetTranslateBench.cpp b/bench/subset/SubsetTranslateBench.cpp
index 27c628edde..d8da6db566 100644
--- a/bench/subset/SubsetTranslateBench.cpp
+++ b/bench/subset/SubsetTranslateBench.cpp
@@ -71,11 +71,8 @@ void SubsetTranslateBench::onDraw(int n, SkCanvas* canvas) {
     if (fUseCodec) {
         for (int count = 0; count < n; count++) {
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
+            SkASSERT(SkCodec::kOutOfOrder_SkScanlineOrder != codec->getScanlineOrder());
             const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
-            SkAutoTDeleteArray<uint8_t> row(nullptr);
-            if (codec->getScanlineOrder() == SkCodec::kTopDown_SkScanlineOrder) {
-                row.reset(new uint8_t[info.minRowBytes()]);
-            }
 
             SkBitmap bitmap;
             // Note that we use the same bitmap for all of the subsets.
@@ -83,17 +80,8 @@ void SubsetTranslateBench::onDraw(int n, SkCanvas* canvas) {
             SkImageInfo subsetInfo = info.makeWH(fSubsetWidth, fSubsetHeight);
             alloc_pixels(&bitmap, subsetInfo, colors, colorCount);
 
-            const uint32_t bpp = info.bytesPerPixel();
-
             for (int x = 0; x < info.width(); x += fSubsetWidth) {
                 for (int y = 0; y < info.height(); y += fSubsetHeight) {
-                    SkDEBUGCODE(SkCodec::Result result =)
-                    codec->startScanlineDecode(info, nullptr, get_colors(&bitmap), &colorCount);
-                    SkASSERT(SkCodec::kSuccess == result);
-
-                    SkDEBUGCODE(int lines =) codec->skipScanlines(y);
-                    SkASSERT(y == lines);
-
                     const uint32_t currSubsetWidth =
                             x + (int) fSubsetWidth > info.width() ?
                             info.width() - x : fSubsetWidth;
@@ -101,38 +89,22 @@ void SubsetTranslateBench::onDraw(int n, SkCanvas* canvas) {
                             y + (int) fSubsetHeight > info.height() ?
                             info.height() - y : fSubsetHeight;
 
-                    switch (codec->getScanlineOrder()) {
-                        case SkCodec::kTopDown_SkScanlineOrder:
-                            for (uint32_t y = 0; y < currSubsetHeight; y++) {
-                                SkDEBUGCODE(lines =) codec->getScanlines(row.get(), 1, 0);
-                                SkASSERT(1 == lines);
-
-                                memcpy(bitmap.getAddr(0, y), row.get() + x * bpp,
-                                        currSubsetWidth * bpp);
-                            }
-                            break;
-                        case SkCodec::kNone_SkScanlineOrder: {
-                            // decode all scanlines that intersect the subset, and copy the subset
-                            // into the output.
-                            SkImageInfo stripeInfo = info.makeWH(info.width(), currSubsetHeight);
-                            SkBitmap stripeBm;
-                            alloc_pixels(&stripeBm, stripeInfo, colors, colorCount);
-
-                            SkDEBUGCODE(lines =) codec->getScanlines(stripeBm.getPixels(),
-                                    currSubsetHeight, stripeBm.rowBytes());
-                            SkASSERT(currSubsetHeight == (uint32_t) lines);
-
-                            for (uint32_t subsetY = 0; subsetY < currSubsetHeight; subsetY++) {
-                                memcpy(bitmap.getAddr(0, subsetY), stripeBm.getAddr(x, subsetY),
-                                        currSubsetWidth * bpp);
-                            }
-                            break;
-                        }
-                        default:
-                            // We currently are only testing kTopDown and kNone, which are the only
-                            // two used by the subsets we care about. skbug.com/4428
-                            SkASSERT(false);
-                    }
+                    // The scanline decoder will handle subsetting in the x-dimension.
+                    SkIRect subset = SkIRect::MakeXYWH(x, 0, currSubsetWidth,
+                            codec->getInfo().height());
+                    SkCodec::Options options;
+                    options.fSubset = &subset;
+
+                    SkDEBUGCODE(SkCodec::Result result =)
+                    codec->startScanlineDecode(info, &options, get_colors(&bitmap), &colorCount);
+                    SkASSERT(SkCodec::kSuccess == result);
+
+                    SkDEBUGCODE(bool success =) codec->skipScanlines(y);
+                    SkASSERT(success);
+
+                    SkDEBUGCODE(uint32_t lines =) codec->getScanlines(bitmap.getPixels(),
+                            currSubsetHeight, bitmap.rowBytes());
+                    SkASSERT(currSubsetHeight == lines);
                 }
             }
         }
diff --git a/bench/subset/SubsetZoomBench.cpp b/bench/subset/SubsetZoomBench.cpp
index 3edc17f1cb..f17a97c26b 100644
--- a/bench/subset/SubsetZoomBench.cpp
+++ b/bench/subset/SubsetZoomBench.cpp
@@ -61,69 +61,41 @@ void SubsetZoomBench::onDraw(int n, SkCanvas* canvas) {
     if (fUseCodec) {
         for (int count = 0; count < n; count++) {
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
+            SkASSERT(SkCodec::kOutOfOrder_SkScanlineOrder != codec->getScanlineOrder());
             const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
-            SkAutoTDeleteArray<uint8_t> row(nullptr);
-            if (codec->getScanlineOrder() == SkCodec::kTopDown_SkScanlineOrder) {
-                row.reset(new uint8_t[info.minRowBytes()]);
-            }
 
             const int centerX = info.width() / 2;
             const int centerY = info.height() / 2;
             int w = fSubsetWidth;
             int h = fSubsetHeight;
             do {
-                SkDEBUGCODE(SkCodec::Result result = )
-                codec->startScanlineDecode(info, nullptr, colors, &colorCount);
-                SkASSERT(SkCodec::kSuccess == result);
-
                 const int subsetStartX = SkTMax(0, centerX - w / 2);
                 const int subsetStartY = SkTMax(0, centerY - h / 2);
                 const int subsetWidth = SkTMin(w, info.width() - subsetStartX);
                 const int subsetHeight = SkTMin(h, info.height() - subsetStartY);
+
+                // The scanline decoder will handle subsetting in the x-dimension.
+                SkIRect subset = SkIRect::MakeXYWH(subsetStartX, 0, subsetWidth,
+                        codec->getInfo().height());
+                SkCodec::Options options;
+                options.fSubset = &subset;
+
+                SkDEBUGCODE(SkCodec::Result result = )
+                codec->startScanlineDecode(info, &options, colors, &colorCount);
+                SkASSERT(SkCodec::kSuccess == result);
+
                 // Note that if we subsetted and scaled in a single step, we could use the
                 // same bitmap - as is often done in actual use cases.
                 SkBitmap bitmap;
                 SkImageInfo subsetInfo = info.makeWH(subsetWidth, subsetHeight);
                 alloc_pixels(&bitmap, subsetInfo, colors, colorCount);
 
-                uint32_t bpp = info.bytesPerPixel();
-
-                SkDEBUGCODE(int lines = ) codec->skipScanlines(subsetStartY);
-                SkASSERT(subsetStartY == lines);
-
-                switch (codec->getScanlineOrder()) {
-                    case SkCodec::kTopDown_SkScanlineOrder:
-                        for (int y = 0; y < subsetHeight; y++) {
-                            SkDEBUGCODE(lines = ) codec->getScanlines(row.get(), 1, 0);
-                            SkASSERT(1 == lines);
-
-                            memcpy(bitmap.getAddr(0, y), row.get() + subsetStartX * bpp,
-                                    subsetWidth * bpp);
-                        }
-                        break;
-                    case SkCodec::kNone_SkScanlineOrder: {
-                        // decode all scanlines that intersect the subset, and copy the subset
-                        // into the output.
-                        SkImageInfo stripeInfo = info.makeWH(info.width(), subsetHeight);
-                        SkBitmap stripeBm;
-                        alloc_pixels(&stripeBm, stripeInfo, colors, colorCount);
-
-                        SkDEBUGCODE(lines = ) codec->getScanlines(stripeBm.getPixels(),
-                                subsetHeight, stripeBm.rowBytes());
-                        SkASSERT(subsetHeight == lines);
-
-                        for (int y = 0; y < subsetHeight; y++) {
-                            memcpy(bitmap.getAddr(0, y),
-                                   stripeBm.getAddr(subsetStartX, y),
-                                   subsetWidth * bpp);
-                        }
-                        break;
-                    }
-                    default:
-                        // We currently are only testing kTopDown and kNone, which are the only
-                        // two used by the subsets we care about. skbug.com/4428
-                        SkASSERT(false);
-                }
+                SkDEBUGCODE(bool success = ) codec->skipScanlines(subsetStartY);
+                SkASSERT(success);
+
+                SkDEBUGCODE(int lines = ) codec->getScanlines(bitmap.getPixels(),
+                        subsetHeight, bitmap.rowBytes());
+                SkASSERT(subsetHeight == lines);
 
                 w <<= 1;
                 h <<= 1;