Add subsetting to SkScaledCodec

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 "SkBitmapRegionDecoderPriv.h"
 #include "SkCanvas.h"
+#include "SkCodecPriv.h"
 
 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
     : INHERITED(decoder->getInfo().width(), decoder->getInfo().height())
     , fDecoder(decoder)
 {}
 
 /*
- * Chooses the correct image subset offsets and dimensions for the partial decode.
- */
-static inline void set_subset_region(int inputOffset, int inputDimension,
-        int imageOriginalDimension, int* imageSubsetOffset, int* outOffset,
-        int* imageSubsetDimension) {
-
-    // This must be at least zero, we can't start decoding the image at a negative coordinate.
-    *imageSubsetOffset = SkTMax(0, inputOffset);
-
-    // If inputOffset is less than zero, we decode to an offset location in the output bitmap.
-    *outOffset = *imageSubsetOffset - inputOffset;
-
-    // Use imageSusetOffset to make sure we don't decode pixels past the edge of the image.
-    // Use outOffset to make sure we don't decode pixels past the edge of the region.
-    *imageSubsetDimension = SkTMin(imageOriginalDimension - *imageSubsetOffset,
-            inputDimension - *outOffset);
-}
-
-/*
- * Returns a scaled dimension based on the original dimension and the sample size.
- * TODO: Share this implementation with SkScaledCodec.
- */
-static int get_scaled_dimension(int srcDimension, int sampleSize) {
-    if (sampleSize > srcDimension) {
-        return 1;
-    }
-    return srcDimension / sampleSize;
-}
-
-/*
  * 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) {
     // Reject color types not supported by this method
     if (kIndex_8_SkColorType == dstColorType || kGray_8_SkColorType == dstColorType) {
-        SkDebugf("Error: Color type not supported.\n");
+        SkCodecPrintf("Error: Color type not supported.\n");
         return nullptr;
     }
 
+    // Fix the input sampleSize if necessary.
+    if (sampleSize < 1) {

[scroggo, 2015/10/02 18:27:03]

Is this just in case? Or were you seeing bad input?

[msarett, 2015/10/06 23:01:27]

The Android code likes to call decodeRegion with sampleSize = 0 when it really
means 1.  Of course, since Android is not a client of code right now, this seems
unnecessary.

[scroggo, 2015/10/07 17:49:39]

Oh, weird, it looks like BitmapFactory.Options.inSampleSize never gets a default
value, so it is 0, and SkImageDecoder does this same fix.

If we do not account for it here, we'll need to make sure the Android code does
not rely on it. I think it's reasonable to account for it here though, in the
interest of being robust.

+        sampleSize = 1;
+    }
+
     // The client may not necessarily request a region that is fully within
     // the image.  We may need to do some calculation to determine what part
     // of the image to decode.
 
     // The left offset of the portion of the image we want, where zero
     // indicates the left edge of the image.
     int imageSubsetX;
 
     // The size of the output bitmap is determined by the size of the
     // requested region, not by the size of the intersection of the region
     // and the image dimensions.  If inputX is negative, we will need to
     // place decoded pixels into the output bitmap starting at a left offset.
     // If this is non-zero, imageSubsetX must be zero.
     int outX;
 
     // The width of the portion of the image that we will write to the output
     // bitmap.  If the region is not fully contained within the image, this
     // will not be the same as inputWidth.
     int imageSubsetWidth;
-    set_subset_region(inputX, inputWidth, this->width(), &imageSubsetX, &outX, &imageSubsetWidth);
+    bool imageContainsEntireSubset = set_subset_region(inputX, inputWidth, this->width(),
+            &imageSubsetX, &outX, &imageSubsetWidth);
 
     // The top offset of the portion of the image we want, where zero
     // indicates the top edge of the image.
     int imageSubsetY;
 
     // The size of the output bitmap is determined by the size of the
     // requested region, not by the size of the intersection of the region
     // and the image dimensions.  If inputY is negative, we will need to
     // place decoded pixels into the output bitmap starting at a top offset.
     // If this is non-zero, imageSubsetY must be zero.
     int outY;
 
     // The height of the portion of the image that we will write to the output
     // bitmap.  If the region is not fully contained within the image, this
     // will not be the same as inputHeight.
     int imageSubsetHeight;
-    set_subset_region(inputY, inputHeight, this->height(), &imageSubsetY, &outY,
-            &imageSubsetHeight);
+    imageContainsEntireSubset &= set_subset_region(inputY, inputHeight, this->height(),
+            &imageSubsetY, &outY, &imageSubsetHeight);
 
     if (imageSubsetWidth <= 0 || imageSubsetHeight <= 0) {
-        SkDebugf("Error: Region must intersect part of the image.\n");
+        SkCodecPrintf("Error: Region must intersect part of the image.\n");
         return nullptr;
     }
 
     // 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) {
-        SkDebugf("Error: Could not start scanline decoder.\n");
+        SkCodecPrintf("Error: Could not start scanline decoder.\n");
         return nullptr;
     }
 
     // Allocate a bitmap for the unscaled decode
     SkBitmap tmp;
     SkImageInfo tmpInfo = decodeInfo.makeWH(this->width(), imageSubsetHeight);
     if (!tmp.tryAllocPixels(tmpInfo)) {
-        SkDebugf("Error: Could not allocate pixels.\n");
+        SkCodecPrintf("Error: Could not allocate pixels.\n");
         return nullptr;
     }
 
     // Skip the unneeded rows
     if (!fDecoder->skipScanlines(imageSubsetY)) {
-        SkDebugf("Error: Failed to skip scanlines.\n");
+        SkCodecPrintf("Error: Failed to skip scanlines.\n");
         return nullptr;
     }
 
     // Decode the necessary rows
     fDecoder->getScanlines(tmp.getAddr(0, 0), imageSubsetHeight, tmp.rowBytes());
 
     // Calculate the size of the output
     const int outWidth = get_scaled_dimension(inputWidth, sampleSize);
     const int outHeight = get_scaled_dimension(inputHeight, sampleSize);
 
     // Initialize the destination bitmap
     SkAutoTDelete<SkBitmap> bitmap(new SkBitmap());
     SkImageInfo dstInfo = decodeInfo.makeWH(outWidth, outHeight);
     if (!bitmap->tryAllocPixels(dstInfo)) {
-        SkDebugf("Error: Could not allocate pixels.\n");
+        SkCodecPrintf("Error: Could not allocate pixels.\n");
         return nullptr;
     }
 
     // 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 (0 != outX || 0 != outY ||
-            inputX + inputWidth > this->width() ||
-            inputY + inputHeight > this->height()) {
+    if (!imageContainsEntireSubset) {
         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) imageSubsetX, (SkScalar) 0,
             (SkScalar) imageSubsetWidth, (SkScalar) imageSubsetHeight);
     SkRect dst = SkRect::MakeXYWH((SkScalar) (outX / sampleSize), (SkScalar) (outY / sampleSize),
             (SkScalar) get_scaled_dimension(imageSubsetWidth, sampleSize),
             (SkScalar) get_scaled_dimension(imageSubsetHeight, 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();
 }
+
+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());
+}