Add subsetting to SkScaledCodec

tools/SkBitmapRegionCanvas.cpp

Index: tools/SkBitmapRegionCanvas.cpp
diff --git a/tools/SkBitmapRegionCanvas.cpp b/tools/SkBitmapRegionCanvas.cpp
index 086ac19864b3a15e96dae61d26a835eca43cb269..0ed95cbe1528de7d3edd4356ffd0bbece7804de9 100644
--- a/tools/SkBitmapRegionCanvas.cpp
+++ b/tools/SkBitmapRegionCanvas.cpp
@@ -6,7 +6,9 @@
  */
 
 #include "SkBitmapRegionCanvas.h"
+#include "SkBitmapRegionDecoderPriv.h"
 #include "SkCanvas.h"
+#include "SkCodecPriv.h"
 
 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
     : INHERITED(decoder->getInfo().width(), decoder->getInfo().height())
@@ -14,36 +16,6 @@ SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* 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.
@@ -56,10 +28,15 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
                                              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.
@@ -79,7 +56,8 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // 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.
@@ -96,11 +74,11 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // 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;
     }
 
@@ -111,11 +89,11 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     }
     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;
     }
 
@@ -123,13 +101,13 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     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;
     }
 
@@ -144,7 +122,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     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;
     }
 
@@ -155,9 +133,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // 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);
     }
 
@@ -177,3 +153,15 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
 
     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());
+}