Fill incomplete images in SkCodec parent class
Rather than implementing some sort of "fill" in every
SkCodec subclass for incomplete images, let's make the
parent class handle this situation.
This includes an API change to SkCodec.h
SkCodec::getScanlines() now returns the number of lines it
read successfully, rather than an SkCodec::Result enum.
getScanlines() most often fails on an incomplete input, in
which case it is useful to know how many lines were
successfully decoded - this provides more information than
kIncomplete vs kSuccess. We do lose information when the
API is used improperly, as we are no longer able to return
kInvalidParameter or kScanlineNotStarted.
Known Issues:
Does not work for incomplete fFrameIsSubset gifs.
Does not work for incomplete icos.
BUG=skia:
Review URL: https://codereview.chromium.org/1332053002
diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 7300a5c..1b9cb0f 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -132,10 +132,6 @@
*/
kCouldNotRewind,
/**
- * startScanlineDecode() was not called before calling getScanlines.
- */
- kScanlineDecodingNotStarted,
- /**
* This method is not implemented by this codec.
* FIXME: Perhaps this should be kUnsupported?
*/
@@ -281,8 +277,11 @@
* @param countLines Number of lines to write.
* @param rowBytes Number of bytes per row. Must be large enough to hold
* a scanline based on the SkImageInfo used to create this object.
+ * @return the number of lines successfully decoded. If this value is
+ * less than countLines, this will fill the remaining lines with a
+ * default value.
*/
- Result getScanlines(void* dst, int countLines, size_t rowBytes);
+ int getScanlines(void* dst, int countLines, size_t rowBytes);
/**
* Skip count scanlines.
@@ -293,8 +292,15 @@
* NOTE: If skipped lines are the only lines with alpha, this default
* will make reallyHasAlpha return true, when it could have returned
* false.
+ *
+ * @return true if the scanlines were successfully skipped
+ * false on failure, possible reasons for failure include:
+ * An incomplete input image stream.
+ * Calling this function before calling startScanlineDecode().
+ * If countLines is less than zero or so large that it moves
+ * the current scanline past the end of the image.
*/
- Result skipScanlines(int countLines);
+ bool skipScanlines(int countLines);
/**
* The order in which rows are output from the scanline decoder is not the
@@ -365,15 +371,24 @@
/**
* Returns the y-coordinate of the next row to be returned by the scanline
- * decoder. This will be overridden in the case of
- * kOutOfOrder_SkScanlineOrder and should be unnecessary in the case of
- * kNone_SkScanlineOrder.
+ * decoder.
+ *
+ * This will equal fCurrScanline, except in the case of strangely
+ * encoded image types (bottom-up bmps, interlaced gifs).
*
* Results are undefined when not in scanline decoding mode.
*/
- int nextScanline() const {
- return this->onNextScanline();
- }
+ int nextScanline() const { return this->outputScanline(fCurrScanline); }
+
+ /**
+ * Returns the output y-coordinate of the row that corresponds to an input
+ * y-coordinate. The input y-coordinate represents where the scanline
+ * is located in the encoded data.
+ *
+ * This will equal inputScanline, except in the case of strangely
+ * encoded image types (bottom-up bmps, interlaced gifs).
+ */
+ int outputScanline(int inputScanline) const;
protected:
SkCodec(const SkImageInfo&, SkStream*);
@@ -394,9 +409,16 @@
virtual SkEncodedFormat onGetEncodedFormat() const = 0;
+ /**
+ * @param rowsDecoded When the encoded image stream is incomplete, this function
+ * will return kIncompleteInput and rowsDecoded will be set to
+ * the number of scanlines that were successfully decoded.
+ * This will allow getPixels() to fill the uninitialized memory.
+ */
virtual Result onGetPixels(const SkImageInfo& info,
void* pixels, size_t rowBytes, const Options&,
- SkPMColor ctable[], int* ctableCount) = 0;
+ SkPMColor ctable[], int* ctableCount,
+ int* rowsDecoded) = 0;
virtual bool onGetValidSubset(SkIRect* /* desiredSubset */) const {
// By default, subsets are not supported.
@@ -427,6 +449,36 @@
}
/**
+ * On an incomplete input, getPixels() and getScanlines() will fill any uninitialized
+ * scanlines. This allows the subclass to indicate what value to fill with.
+ *
+ * @param colorType Destination color type.
+ * @param alphaType Destination alpha type.
+ * @return The value with which to fill uninitialized pixels.
+ *
+ * Note that we can interpret the return value as an SkPMColor, a 16-bit 565 color,
+ * an 8-bit gray color, or an 8-bit index into a color table, depending on the color
+ * type.
+ */
+ uint32_t getFillValue(SkColorType colorType, SkAlphaType alphaType) const {
+ return this->onGetFillValue(colorType, alphaType);
+ }
+
+ /**
+ * Some subclasses will override this function, but this is a useful default for the color
+ * types that we support. Note that for color types that do not use the full 32-bits,
+ * we will simply take the low bits of the fill value.
+ *
+ * kN32_SkColorType: Transparent or Black
+ * kRGB_565_SkColorType: Black
+ * kGray_8_SkColorType: Black
+ * kIndex_8_SkColorType: First color in color table
+ */
+ virtual uint32_t onGetFillValue(SkColorType colorType, SkAlphaType alphaType) const {
+ return kOpaque_SkAlphaType == alphaType ? SK_ColorBLACK : SK_ColorTRANSPARENT;
+ }
+
+ /**
* Get method for the input stream
*/
SkStream* stream() {
@@ -443,11 +495,6 @@
virtual SkScanlineOrder onGetScanlineOrder() const { return kTopDown_SkScanlineOrder; }
/**
- * Most images will be kTopDown and will not need to override this function.
- */
- virtual int onNextScanline() const { return fCurrScanline; }
-
- /**
* Update the next scanline. Used by interlaced png.
*/
void updateNextScanline(int newY) { fCurrScanline = newY; }
@@ -456,6 +503,8 @@
const SkCodec::Options& options() const { return fOptions; }
+ virtual int onOutputScanline(int inputScanline) const;
+
private:
const SkImageInfo fSrcInfo;
SkAutoTDelete<SkStream> fStream;
@@ -485,20 +534,36 @@
}
// Naive default version just calls onGetScanlines on temp memory.
- virtual SkCodec::Result onSkipScanlines(int countLines) {
+ virtual bool onSkipScanlines(int countLines) {
+ // FIXME (msarett): Make this a pure virtual and always override this.
SkAutoMalloc storage(fDstInfo.minRowBytes());
+
// Note that we pass 0 to rowBytes so we continue to use the same memory.
// Also note that while getScanlines checks that rowBytes is big enough,
// onGetScanlines bypasses that check.
// Calling the virtual method also means we do not double count
// countLines.
- return this->onGetScanlines(storage.get(), countLines, 0);
+ return countLines == this->onGetScanlines(storage.get(), countLines, 0);
}
- virtual SkCodec::Result onGetScanlines(void* dst, int countLines,
- size_t rowBytes) {
- return kUnimplemented;
- }
+ virtual int onGetScanlines(void* dst, int countLines, size_t rowBytes) { return 0; }
+
+ /**
+ * On an incomplete decode, getPixels() and getScanlines() will call this function
+ * to fill any uinitialized memory.
+ *
+ * @param dstInfo Contains the destination color type
+ * Contains the destination alpha type
+ * Contains the destination width
+ * The height stored in this info is unused
+ * @param dst Pointer to the start of destination pixel memory
+ * @param rowBytes Stride length in destination pixel memory
+ * @param zeroInit Indicates if memory is zero initialized
+ * @param linesRequested Number of lines that the client requested
+ * @param linesDecoded Number of lines that were successfully decoded
+ */
+ void fillIncompleteImage(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
+ ZeroInitialized zeroInit, int linesRequested, int linesDecoded);
/**
* Return an object which will allow forcing scanline decodes to sample in X.
@@ -508,9 +573,8 @@
*
* Only valid during scanline decoding.
*/
- virtual SkSampler* getSampler() { return nullptr; }
+ virtual SkSampler* getSampler(bool createIfNecessary) { return nullptr; }
- // Needed to call getSampler and dimensionsSupported.
friend class SkScaledCodec;
};
#endif // SkCodec_DEFINED