Refactor SkBitmapRegionDecoderInterface for Android

tools/SkBitmapRegionCanvas.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 "SkBitmapRegionCanvas.h"
 #include "SkCanvas.h"
 #include "SkCodecPriv.h"
 #include "SkCodecTools.h"
 
 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
     : INHERITED(decoder->getInfo().width(), decoder->getInfo().height())
     , fDecoder(decoder)
 {}
 
-/*
- * Three differences from the Android version:
- *     Returns a Skia bitmap instead of an Android bitmap.
- *     Android version attempts to reuse a recycled bitmap.
- *     Removed the options object and used parameters for color type and
- *     sample size.
- */
-SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
-                                             int inputWidth, int inputHeight,
-                                             int sampleSize,
-                                             SkColorType dstColorType) {
+bool SkBitmapRegionCanvas::decodeRegion(SkBitmap* bitmap, SkBitmap::Allocator* allocator,
+        const SkIRect& desiredSubset, int sampleSize, SkColorType dstColorType,
+        bool requireUnpremul) {
     // Reject color types not supported by this method
     if (kIndex_8_SkColorType == dstColorType || kGray_8_SkColorType == dstColorType) {
         SkCodecPrintf("Error: Color type not supported.\n");
-        return nullptr;
+        return false;
     }
 
+    // Reject requests for unpremultiplied alpha
+    if (requireUnpremul) {
+        SkCodecPrintf("Error: Alpha type not supported.\n");
+        return false;
+    }
+    SkAlphaType dstAlphaType = fDecoder->getInfo().alphaType();
+    if (kUnpremul_SkAlphaType == dstAlphaType) {
+        dstAlphaType = kPremul_SkAlphaType;
+    }
+
+    // FIXME: Can we add checks and support kIndex8 or unpremultiplied alpha in special cases?
+
     // Fix the input sampleSize if necessary.
     if (sampleSize < 1) {
         sampleSize = 1;
     }
 
     // The size of the output bitmap is determined by the size of the
     // requested subset, not by the size of the intersection of the subset
     // and the image dimensions.
     // If inputX is negative, we will need to place decoded pixels into the
     // output bitmap starting at a left offset.  Call this outX.
     // If outX is non-zero, subsetX must be zero.
     // If inputY is negative, we will need to place decoded pixels into the
     // output bitmap starting at a top offset.  Call this outY.
     // If outY is non-zero, subsetY must be zero.
     int outX;
     int outY;
-    SkIRect subset = SkIRect::MakeXYWH(inputX, inputY, inputWidth, inputHeight);
+    SkIRect subset = desiredSubset;
     SubsetType type = adjust_subset_rect(fDecoder->getInfo().dimensions(), &subset, &outX, &outY);
     if (SubsetType::kOutside_SubsetType == type) {
-        return nullptr;
+        return false;
     }
 
     // Create the image info for the decode
-    SkAlphaType dstAlphaType = fDecoder->getInfo().alphaType();
-    if (kUnpremul_SkAlphaType == dstAlphaType) {
-        dstAlphaType = kPremul_SkAlphaType;
-    }
     SkImageInfo decodeInfo = SkImageInfo::Make(this->width(), this->height(),
             dstColorType, dstAlphaType);
 
     // Start the scanline decoder
     SkCodec::Result r = fDecoder->startScanlineDecode(decodeInfo);
     if (SkCodec::kSuccess != r) {
         SkCodecPrintf("Error: Could not start scanline decoder.\n");
-        return nullptr;
+        return false;
     }
 
     // Allocate a bitmap for the unscaled decode
     SkBitmap tmp;
     SkImageInfo tmpInfo = decodeInfo.makeWH(this->width(), subset.height());
     if (!tmp.tryAllocPixels(tmpInfo)) {
         SkCodecPrintf("Error: Could not allocate pixels.\n");
-        return nullptr;
+        return false;
     }
 
     // Skip the unneeded rows
     if (!fDecoder->skipScanlines(subset.y())) {
         SkCodecPrintf("Error: Failed to skip scanlines.\n");
-        return nullptr;
+        return false;
     }
 
     // Decode the necessary rows
     fDecoder->getScanlines(tmp.getAddr(0, 0), subset.height(), tmp.rowBytes());
 
     // Calculate the size of the output
-    const int outWidth = get_scaled_dimension(inputWidth, sampleSize);
-    const int outHeight = get_scaled_dimension(inputHeight, sampleSize);
+    const int outWidth = get_scaled_dimension(desiredSubset.width(), sampleSize);
+    const int outHeight = get_scaled_dimension(desiredSubset.height(), sampleSize);
 
     // Initialize the destination bitmap
-    SkAutoTDelete<SkBitmap> bitmap(new SkBitmap());
     SkImageInfo dstInfo = decodeInfo.makeWH(outWidth, outHeight);
-    if (!bitmap->tryAllocPixels(dstInfo)) {
+    bitmap->setInfo(dstInfo, dstInfo.minRowBytes());
+    if (!bitmap->tryAllocPixels(allocator, nullptr)) {
         SkCodecPrintf("Error: Could not allocate pixels.\n");
-        return nullptr;
+        return false;
     }
 
     // Zero the bitmap if the region is not completely within the image.
     // TODO (msarett): Can we make this faster by implementing it to only
     //                 zero parts of the image that we won't overwrite with
     //                 pixels?
     // TODO (msarett): This could be skipped if memory is zero initialized.
     //                 This would matter if this code is moved to Android and
     //                 uses Android bitmaps.
     if (SubsetType::kPartiallyInside_SubsetType == type) {
         bitmap->eraseColor(0);
     }
 
     // Use a canvas to crop and scale to the destination bitmap
     SkCanvas canvas(*bitmap);
     // TODO (msarett): Maybe we can take advantage of the fact that SkRect uses floats?
     SkRect src = SkRect::MakeXYWH((SkScalar) subset.x(), (SkScalar) 0,
             (SkScalar) subset.width(), (SkScalar) subset.height());
     SkRect dst = SkRect::MakeXYWH((SkScalar) (outX / sampleSize), (SkScalar) (outY / sampleSize),
             (SkScalar) get_scaled_dimension(subset.width(), sampleSize),
             (SkScalar) get_scaled_dimension(subset.height(), sampleSize));
     SkPaint paint;
     // Overwrite the dst with the src pixels
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     // TODO (msarett): Test multiple filter qualities.  kNone is the default.
     canvas.drawBitmapRect(tmp, src, dst, &paint);
 
-    return bitmap.detach();
+    return true;
 }
 
 bool SkBitmapRegionCanvas::conversionSupported(SkColorType colorType) {
     // SkCanvas does not draw to these color types.
     if (kIndex_8_SkColorType == colorType || kGray_8_SkColorType == colorType) {
         return false;
     }
 
     // FIXME: Call virtual function when it lands.
     SkImageInfo info = SkImageInfo::Make(0, 0, colorType, fDecoder->getInfo().alphaType(),
             fDecoder->getInfo().profileType());
     return conversion_possible(info, fDecoder->getInfo());
 }