Subset decoding benchmarks

bench/subset/SubsetZoomBench.cpp

Index: bench/subset/SubsetZoomBench.cpp
diff --git a/bench/subset/SubsetZoomBench.cpp b/bench/subset/SubsetZoomBench.cpp
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+/*
+ * 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 "SubsetZoomBench.h"
+#include "SubsetBenchPriv.h"
+#include "SkData.h"
+#include "SkCodec.h"
+#include "SkImageDecoder.h"
+#include "SkOSFile.h"
+#include "SkStream.h"
+
+/*
+ *
+ * This benchmark is designed to test the performance of subset decoding.
+ * Choose subsets to mimic a user zooming in or out on a photo.
+ *
+ */
+
+SubsetZoomBench::SubsetZoomBench(const SkString& path,
+                                 SkColorType colorType,
+                                 uint32_t subsetWidth,
+                                 uint32_t subsetHeight,
+                                 bool useCodec)
+    : fColorType(colorType)
+    , fSubsetWidth(subsetWidth)
+    , fSubsetHeight(subsetHeight)
+    , fUseCodec(useCodec)
+{
+    // Parse the filename
+    SkString baseName = SkOSPath::Basename(path.c_str());
+
+    // Choose an informative color name
+    const char* colorName = get_color_name(fColorType);
+
+    fName.printf("%sSubsetZoom_%dx%d_%s_%s", fUseCodec ? "Codec" : "Image", fSubsetWidth,
+            fSubsetHeight, baseName.c_str(), colorName);
+    
+    // Perform the decode setup
+    SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(path.c_str()));
+    fStream.reset(new SkMemoryStream(encoded));
+}
+
+const char* SubsetZoomBench::onGetName() {
+    return fName.c_str();
+}
+
+bool SubsetZoomBench::isSuitableFor(Backend backend) {
+    return kNonRendering_Backend == backend;
+}
+
+void SubsetZoomBench::onDraw(const int n, SkCanvas* canvas) {
+    // When the color type is kIndex8, we will need to store the color table.  If it is
+    // used, it will be initialized by the codec.
+    int colorCount;
+    SkPMColor colors[256];
+    if (fUseCodec) {
+        for (int count = 0; count < n; count++) {
+            SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
+            const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
+            SkAutoTDeleteArray<uint8_t> row(SkNEW_ARRAY(uint8_t, info.minRowBytes()));
+            SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(
+                    info, NULL, colors, &colorCount);
+
+            const int centerX = info.width() / 2;
+            const int centerY = info.height() / 2;
+            int w = fSubsetWidth;
+            int h = fSubsetHeight;
+            do {
+                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);
+                // 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;
+                bitmap.allocPixels(info.makeWH(subsetWidth, subsetHeight));
+
+                uint32_t bpp = info.bytesPerPixel();
+                scanlineDecoder->skipScanlines(subsetStartY);
+                for (int y = 0; y < subsetHeight; y++) {
+                    scanlineDecoder->getScanlines(row.get(), 1, 0);
+                    memcpy(bitmap.getAddr(0, y), row.get() + subsetStartX * bpp,
+                            subsetWidth * bpp);
+                }
+                w <<= 1;
+                h <<= 1;
+            } while (w < 2 * info.width() || h < 2 * info.height());
+        }
+    } else {
+        for (int count = 0; count < n; count++) {
+            int width, height;
+            SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(fStream));
+            decoder->buildTileIndex(fStream->duplicate(), &width, &height);
+
+            const int centerX = width / 2;
+            const int centerY = height / 2;
+            int w = fSubsetWidth;
+            int h = fSubsetHeight;
+            do {
+                const int subsetStartX = SkTMax(0, centerX - w / 2);
+                const int subsetStartY = SkTMax(0, centerY - h / 2);
+                const int subsetWidth = SkTMin(w, width - subsetStartX);
+                const int subsetHeight = SkTMin(h, height - subsetStartY);
+                SkBitmap bitmap;
+                SkIRect rect = SkIRect::MakeXYWH(subsetStartX, subsetStartY, subsetWidth,
+                        subsetHeight);
+                decoder->decodeSubset(&bitmap, rect, fColorType);
+                w <<= 1;
+                h <<= 1;
+            } while (w < 2 * width || h < 2 * height);
+        }
+    }
+}