Chromium Code Reviews
chromiumcodereview-hr@appspot.gserviceaccount.com (chromiumcodereview-hr) | Please choose your nickname with Settings | Help | Chromium Project | Gerrit Changes | Sign out
(11)

Unified Diff: include/codec/SkCodec.h

Issue 1365313002: Merge SkCodec with SkScanlineDecoder (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Skip ICO in SkScaledCodec for now Created 5 years, 3 months ago
Use n/p to move between diff chunks; N/P to move between comments. Draft comments are only viewable by you.
Jump to:
View side-by-side diff with in-line comments
Download patch
« no previous file with comments | « gyp/codec.gyp ('k') | include/codec/SkScaledCodec.h » ('j') | no next file with comments »
Expand Comments ('e') | Collapse Comments ('c') | Show Comments Hide Comments ('s')
Index: include/codec/SkCodec.h
diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index bdfa2326fba5acc4c89bdc346e2b972a0ddb25d4..01fd4fa62a0a2aeeb40f337200518a30bab80f60 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -45,7 +45,7 @@ public:
/**
* Return the ImageInfo associated with this codec.
*/
- const SkImageInfo& getInfo() const { return fInfo; }
+ const SkImageInfo& getInfo() const { return fSrcInfo; }
/**
* Return a size that approximately supports the desired scale factor.
@@ -131,7 +131,12 @@ public:
*/
kCouldNotRewind,
/**
- * This method is not implemented by this generator.
+ * startScanlineDecode() was not called before calling getScanlines.
+ */
+ kScanlineDecodingNotStarted,
+ /**
+ * This method is not implemented by this codec.
+ * FIXME: Perhaps this should be kUnsupported?
*/
kUnimplemented,
};
@@ -202,6 +207,9 @@ public:
* If info is not kIndex8_SkColorType, then the last two parameters may be NULL. If ctableCount
* is not null, it will be set to 0.
*
+ * If a scanline decode is in progress, scanline mode will end, requiring the client to call
+ * startScanlineDecode() in order to return to decoding scanlines.
+ *
* @return Result kSuccess, or another value explaining the type of failure.
*/
Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, const Options*,
@@ -225,6 +233,147 @@ public:
return this->onReallyHasAlpha();
}
+ /**
+ * The remaining functions revolve around decoding scanlines.
+ */
+
+ /**
+ * Prepare for a scanline decode with the specified options.
+ *
+ * After this call, this class will be ready to decode the first scanline.
+ *
+ * This must be called in order to call getScanlines or skipScanlines.
+ *
+ * This may require rewinding the stream.
+ *
+ * Not all SkCodecs support this.
+ *
+ * @param dstInfo Info of the destination. If the dimensions do not match
+ * those of getInfo, this implies a scale.
+ * @param options Contains decoding options, including if memory is zero
+ * initialized.
+ * @param ctable A pointer to a color table. When dstInfo.colorType() is
+ * kIndex8, this should be non-NULL and have enough storage for 256
+ * colors. The color table will be populated after decoding the palette.
+ * @param ctableCount A pointer to the size of the color table. When
+ * dstInfo.colorType() is kIndex8, this should be non-NULL. It will
+ * be modified to the true size of the color table (<= 256) after
+ * decoding the palette.
+ * @return Enum representing success or reason for failure.
+ */
+ Result startScanlineDecode(const SkImageInfo& dstInfo, const SkCodec::Options* options,
+ SkPMColor ctable[], int* ctableCount);
+
+ /**
+ * Simplified version of startScanlineDecode() that asserts that info is NOT
+ * kIndex8_SkColorType and uses the default Options.
+ */
+ Result startScanlineDecode(const SkImageInfo& dstInfo);
+
+ /**
+ * Write the next countLines scanlines into dst.
+ *
+ * Not valid to call before calling startScanlineDecode().
+ *
+ * @param dst Must be non-null, and large enough to hold countLines
+ * scanlines of size rowBytes.
+ * @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.
+ */
+ Result getScanlines(void* dst, int countLines, size_t rowBytes);
+
+ /**
+ * Skip count scanlines.
+ *
+ * Not valid to call before calling startScanlineDecode().
+ *
+ * The default version just calls onGetScanlines and discards the dst.
+ * NOTE: If skipped lines are the only lines with alpha, this default
+ * will make reallyHasAlpha return true, when it could have returned
+ * false.
+ */
+ Result skipScanlines(int countLines);
+
+ /**
+ * The order in which rows are output from the scanline decoder is not the
+ * same for all variations of all image types. This explains the possible
+ * output row orderings.
+ */
+ enum SkScanlineOrder {
+ /*
+ * By far the most common, this indicates that the image can be decoded
+ * reliably using the scanline decoder, and that rows will be output in
+ * the logical order.
+ */
+ kTopDown_SkScanlineOrder,
+
+ /*
+ * This indicates that the scanline decoder reliably outputs rows, but
+ * they will be returned in reverse order. If the scanline format is
+ * kBottomUp, the nextScanline() API can be used to determine the actual
+ * y-coordinate of the next output row, but the client is not forced
+ * to take advantage of this, given that it's not too tough to keep
+ * track independently.
+ *
+ * For full image decodes, it is safe to get all of the scanlines at
+ * once, since the decoder will handle inverting the rows as it
+ * decodes.
+ *
+ * For subset decodes and sampling, it is simplest to get and skip
+ * scanlines one at a time, using the nextScanline() API. It is
+ * possible to ask for larger chunks at a time, but this should be used
+ * with caution. As with full image decodes, the decoder will handle
+ * inverting the requested rows, but rows will still be delivered
+ * starting from the bottom of the image.
+ *
+ * Upside down bmps are an example.
+ */
+ kBottomUp_SkScanlineOrder,
+
+ /*
+ * This indicates that the scanline decoder reliably outputs rows, but
+ * they will not be in logical order. If the scanline format is
+ * kOutOfOrder, the nextScanline() API should be used to determine the
+ * actual y-coordinate of the next output row.
+ *
+ * For this scanline ordering, it is advisable to get and skip
+ * scanlines one at a time.
+ *
+ * Interlaced gifs are an example.
+ */
+ kOutOfOrder_SkScanlineOrder,
+
+ /*
+ * Indicates that the entire image must be decoded in order to output
+ * any amount of scanlines. In this case, it is a REALLY BAD IDEA to
+ * request scanlines 1-by-1 or in small chunks. The client should
+ * determine which scanlines are needed and ask for all of them in
+ * a single call to getScanlines().
+ *
+ * Interlaced pngs are an example.
+ */
+ kNone_SkScanlineOrder,
+ };
+
+ /**
+ * An enum representing the order in which scanlines will be returned by
+ * the scanline decoder.
+ */
+ SkScanlineOrder getScanlineOrder() const { return this->onGetScanlineOrder(); }
+
+ /**
+ * 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.
+ *
+ * Results are undefined when not in scanline decoding mode.
+ */
+ int nextScanline() const {
+ return this->onNextScanline();
+ }
+
protected:
SkCodec(const SkImageInfo&, SkStream*);
@@ -275,9 +424,59 @@ protected:
return fStream.get();
}
+ /**
+ * The remaining functions revolve around decoding scanlines.
+ */
+
+ /**
+ * Most images types will be kTopDown and will not need to override this function.
+ */
+ 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; }
+
+ const SkImageInfo& dstInfo() const { return fDstInfo; }
+
+ const SkCodec::Options& options() const { return fOptions; }
+
private:
- const SkImageInfo fInfo;
+ const SkImageInfo fSrcInfo;
SkAutoTDelete<SkStream> fStream;
bool fNeedsRewind;
+ // These fields are only meaningful during scanline decodes.
+ SkImageInfo fDstInfo;
+ SkCodec::Options fOptions;
+ int fCurrScanline;
+
+ // Methods for scanline decoding.
+ virtual SkCodec::Result onStartScanlineDecode(const SkImageInfo& dstInfo,
+ const SkCodec::Options& options, SkPMColor ctable[], int* ctableCount) {
+ return kUnimplemented;
+ }
+
+ // Naive default version just calls onGetScanlines on temp memory.
+ virtual SkCodec::Result onSkipScanlines(int countLines) {
+ 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);
+ }
+
+ virtual SkCodec::Result onGetScanlines(void* dst, int countLines,
+ size_t rowBytes) {
+ return kUnimplemented;
+ }
+
};
#endif // SkCodec_DEFINED
« no previous file with comments | « gyp/codec.gyp ('k') | include/codec/SkScaledCodec.h » ('j') | no next file with comments »

Powered by Google App Engine
This is Rietveld 408576698