Scanline decoding for bmp
Redesigns SkScanlineDecoder.h to indicate the ordering
in which the scanlines are provided
Refactors SkSwizzler::Fill() to include the zeroInit check
and to actually be correct.
BUG=skia:3257
BUG=skia:4198
Review URL: https://codereview.chromium.org/1287423002
diff --git a/src/codec/SkBmpCodec.h b/src/codec/SkBmpCodec.h
index ee14f89..4b2cd2a 100644
--- a/src/codec/SkBmpCodec.h
+++ b/src/codec/SkBmpCodec.h
@@ -11,6 +11,7 @@
#include "SkColorTable.h"
#include "SkImageInfo.h"
#include "SkMaskSwizzler.h"
+#include "SkScanlineDecoder.h"
#include "SkStream.h"
#include "SkSwizzler.h"
#include "SkTypes.h"
@@ -23,14 +24,6 @@
public:
/*
- * Describes if rows of the input start at the top or bottom of the image
- */
- enum RowOrder {
- kTopDown_RowOrder,
- kBottomUp_RowOrder
- };
-
- /*
* Checks the start of the stream to see if the image is a bmp
*/
static bool IsBmp(SkStream*);
@@ -48,10 +41,17 @@
*/
static SkCodec* NewFromIco(SkStream*);
+ /*
+ * Assumes IsBmp was called and returned true
+ * Creates a bmp scanline decoder
+ * Takes ownership of the stream
+ */
+ static SkScanlineDecoder* NewSDFromStream(SkStream* stream);
+
protected:
SkBmpCodec(const SkImageInfo& info, SkStream* stream, uint16_t bitsPerPixel,
- RowOrder rowOrder);
+ SkScanlineDecoder::SkScanlineOrder rowOrder);
SkEncodedFormat onGetEncodedFormat() const override { return kBMP_SkEncodedFormat; }
@@ -77,6 +77,19 @@
}
/*
+ * Get the destination row number corresponding to the encoded row number.
+ * For kTopDown, we simply return y, but for kBottomUp, the rows will be
+ * decoded in reverse order.
+ *
+ * @param y Iterates from 0 to height, indicating the current row.
+ * @param height The height of the current subset of the image that we are
+ * decoding. This is generally equal to the full height
+ * when we want to decode the full or one when we are
+ * sampling.
+ */
+ int32_t getDstRow(int32_t y, int32_t height);
+
+ /*
* Get the destination row to start filling from
* Used to fill the remainder of the image on incomplete input for bmps
* This is tricky since bmps may be kTopDown or kBottomUp. For kTopDown,
@@ -94,7 +107,26 @@
* Accessors used by subclasses
*/
uint16_t bitsPerPixel() const { return fBitsPerPixel; }
- RowOrder rowOrder() const { return fRowOrder; }
+ SkScanlineDecoder::SkScanlineOrder rowOrder() const { return fRowOrder; }
+
+ /*
+ * To be overriden by bmp subclasses, which provide unique implementations.
+ * Performs subclass specific setup.
+ *
+ * @param dstInfo Contains output information. Height specifies
+ * the total number of rows that will be decoded.
+ * @param options Additonal options to pass to the decoder.
+ * @param inputColorPtr Client-provided memory for a color table. Must
+ * be enough for 256 colors. This will be
+ * populated with colors if the encoded image uses
+ * a color table.
+ * @param inputColorCount If the encoded image uses a color table, this
+ * will be set to the number of colors in the
+ * color table.
+ */
+ virtual SkCodec::Result prepareToDecode(const SkImageInfo& dstInfo,
+ const SkCodec::Options& options, SkPMColor inputColorPtr[],
+ int* inputColorCount) = 0;
private:
@@ -104,8 +136,27 @@
*/
static SkCodec* NewFromStream(SkStream*, bool inIco);
- const uint16_t fBitsPerPixel;
- const RowOrder fRowOrder;
+ /*
+ * Decodes the next dstInfo.height() lines.
+ *
+ * onGetPixels() uses this for full image decodes.
+ * SkScaledCodec::onGetPixels() uses the scanline decoder to call this with
+ * dstInfo.height() = 1, in order to implement sampling.
+ * A potential future use is to allow the caller to decode a subset of the
+ * lines in the image.
+ *
+ * @param dstInfo Contains output information. Height specifies the
+ * number of rows to decode at this time.
+ * @param dst Memory location to store output pixels
+ * @param dstRowBytes Bytes in a row of the destination
+ */
+ virtual Result decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
+ const Options& opts) = 0;
+
+ const uint16_t fBitsPerPixel;
+ const SkScanlineDecoder::SkScanlineOrder fRowOrder;
+
+ friend class SkBmpScanlineDecoder;
typedef SkCodec INHERITED;
};