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Unified Diff: src/codec/SkCodec_libbmp.h

Issue 947283002: Bmp Image Decoding (Closed) Base URL: https://skia.googlesource.com/skia.git@decode-leon-3
Patch Set: Original change plus fix Created 5 years, 9 months ago
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Index: src/codec/SkCodec_libbmp.h
diff --git a/src/codec/SkCodec_libbmp.h b/src/codec/SkCodec_libbmp.h
new file mode 100644
index 0000000000000000000000000000000000000000..f35b88dc69d880c2f3ec698437bd93298a979692
--- /dev/null
+++ b/src/codec/SkCodec_libbmp.h
@@ -0,0 +1,142 @@
+/*
+ * 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 "SkCodec.h"
+#include "SkImageInfo.h"
+#include "SkMaskSwizzler.h"
+#include "SkStream.h"
+#include "SkSwizzler.h"
+#include "SkTypes.h"
+
+// TODO: rename SkCodec_libbmp files to SkBmpCodec
+// TODO: define a wrapper for SkDebugf that doesn't always print
+/*
+ *
+ * This class implements the decoding for bmp images
+ *
+ */
+class SkBmpCodec : public SkCodec {
+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 bitmap
+ *
+ */
+ static bool IsBmp(SkStream*);
+
+ /*
+ *
+ * Assumes IsBmp was called and returned true
+ * Creates a bitmap decoder
+ * Reads enough of the stream to determine the image format
+ *
+ */
+ static SkCodec* NewFromStream(SkStream*);
+
+protected:
+
+ /*
+ *
+ * Initiates the bitmap decode
+ *
+ */
+ virtual Result onGetPixels(const SkImageInfo& dstInfo, void* dst,
+ size_t dstRowBytes, SkPMColor*,
+ int*) SK_OVERRIDE;
+
+private:
+
+ /*
+ *
+ * Used to define the input format of the bitmap
+ *
+ */
+ enum BitmapInputFormat {
+ kStandard_BitmapInputFormat,
+ kRLE_BitmapInputFormat,
+ kBitMask_BitmapInputFormat,
+ kUnknown_BitmapInputFormat
+ };
+
+ /*
+ *
+ * Performs the bitmap decoding for bit masks input format
+ *
+ */
+ Result decodeMask(const SkImageInfo& dstInfo, void* dst,
+ size_t dstRowBytes);
+
+ /*
+ *
+ * Set an RLE pixel using the color table
+ *
+ */
+ void setRLEPixel(SkPMColor* dst, size_t dstRowBytes, int height,
+ uint32_t x, uint32_t y, uint8_t index);
+
+ /*
+ *
+ * Performs the bitmap decoding for RLE input format
+ *
+ */
+ Result decodeRLE(const SkImageInfo& dstInfo, void* dst,
+ size_t dstRowBytes);
+
+ /*
+ *
+ * Performs the bitmap decoding for standard input format
+ *
+ */
+ Result decode(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes);
+
+ /*
+ *
+ * Creates an instance of the decoder
+ * Called only by NewFromStream
+ *
+ * @param srcInfo contains the source width and height
+ * @param stream the stream of image data
+ * @param bitsPerPixel the number of bits used to store each pixel
+ * @param format the format of the bmp file
+ * @param masks optional color masks for certain bmp formats, passes
+ ownership to SkBmpCodec
+ * @param colorTable array representing the color table for index-based bmp
+ * formats, colors are unpremultiplied, passes ownership
+ * to SkBmpCodec
+ * @param rowOrder indicates whether rows are ordered top-down or bottom-up
+ * @param remainingBytes used only for RLE decodes, as we must decode all
+ * of the data at once rather than row by row
+ * it indicates the amount of data left in the stream
+ * after decoding the headers
+ *
+ */
+ SkBmpCodec(const SkImageInfo& srcInfo, SkStream* stream,
+ uint16_t bitsPerPixel, BitmapInputFormat format,
+ SkMasks* masks, SkPMColor* colorTable,
+ RowOrder rowOrder, uint32_t remainingBytes);
+
+ // Fields
+ const uint16_t fBitsPerPixel;
+ const BitmapInputFormat fInputFormat;
+ SkAutoTDelete<SkMasks> fMasks; // owned
+ const SkAutoTDeleteArray<SkPMColor> fColorTable; // owned, unpremul
+ const RowOrder fRowOrder;
+ const uint32_t fRemainingBytes;
+
+ typedef SkCodec INHERITED;
+};
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