Refactor texture compressors into separate files
R=robertphillips@google.com
Author: krajcevski@google.com
Review URL: https://codereview.chromium.org/403383003
diff --git a/src/utils/SkTextureCompressor.h b/src/utils/SkTextureCompressor.h
index ea57934..a7afe03 100644
--- a/src/utils/SkTextureCompressor.h
+++ b/src/utils/SkTextureCompressor.h
@@ -18,13 +18,18 @@
// Various texture compression formats that we support.
enum Format {
// Alpha only formats.
- kLATC_Format,
- kR11_EAC_Format,
+ kLATC_Format, // 4x4 blocks, compresses A8
+ kR11_EAC_Format, // 4x4 blocks, compresses A8
kLast_Format = kR11_EAC_Format
};
static const int kFormatCnt = kLast_Format + 1;
+ // Returns the size of the compressed data given the width, height, and
+ // desired compression format. If the width and height are not an appropriate
+ // multiple of the block size, then this function returns an error (-1).
+ int GetCompressedDataSize(Format fmt, int width, int height);
+
// Returns an SkData holding a blob of compressed data that corresponds
// to the bitmap. If the bitmap colorType cannot be compressed using the
// associated format, then we return NULL. The caller is responsible for
@@ -44,166 +49,11 @@
typedef bool (*CompressionProc)(uint8_t* dst, const uint8_t* src,
int width, int height, int rowBytes);
- // This class implements a blitter that blits directly into a buffer that will
- // be used as an R11 EAC compressed texture. We compute this buffer by
- // buffering four scan lines and then outputting them all at once. This blitter
- // is only expected to be used with alpha masks, i.e. kAlpha8_SkColorType.
- class R11_EACBlitter : public SkBlitter {
- public:
- R11_EACBlitter(int width, int height, void *compressedBuffer);
- virtual ~R11_EACBlitter() { this->flushRuns(); }
-
- // Blit a horizontal run of one or more pixels.
- virtual void blitH(int x, int y, int width) SK_OVERRIDE {
- // This function is intended to be called from any standard RGB
- // buffer, so we should never encounter it. However, if some code
- // path does end up here, then this needs to be investigated.
- SkFAIL("Not implemented!");
- }
-
- /// Blit a horizontal run of antialiased pixels; runs[] is a *sparse*
- /// zero-terminated run-length encoding of spans of constant alpha values.
- virtual void blitAntiH(int x, int y,
- const SkAlpha antialias[],
- const int16_t runs[]) SK_OVERRIDE;
-
- // Blit a vertical run of pixels with a constant alpha value.
- virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE {
- // This function is currently not implemented. It is not explicitly
- // required by the contract, but if at some time a code path runs into
- // this function (which is entirely possible), it needs to be implemented.
- //
- // TODO (krajcevski):
- // This function will be most easily implemented in one of two ways:
- // 1. Buffer each vertical column value and then construct a list
- // of alpha values and output all of the blocks at once. This only
- // requires a write to the compressed buffer
- // 2. Replace the indices of each block with the proper indices based
- // on the alpha value. This requires a read and write of the compressed
- // buffer, but much less overhead.
- SkFAIL("Not implemented!");
- }
-
- // Blit a solid rectangle one or more pixels wide.
- virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE {
- // Analogous to blitRow, this function is intended for RGB targets
- // and should never be called by this blitter. Any calls to this function
- // are probably a bug and should be investigated.
- SkFAIL("Not implemented!");
- }
-
- // Blit a rectangle with one alpha-blended column on the left,
- // width (zero or more) opaque pixels, and one alpha-blended column
- // on the right. The result will always be at least two pixels wide.
- virtual void blitAntiRect(int x, int y, int width, int height,
- SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE {
- // This function is currently not implemented. It is not explicitly
- // required by the contract, but if at some time a code path runs into
- // this function (which is entirely possible), it needs to be implemented.
- //
- // TODO (krajcevski):
- // This function will be most easily implemented as follows:
- // 1. If width/height are smaller than a block, then update the
- // indices of the affected blocks.
- // 2. If width/height are larger than a block, then construct a 9-patch
- // of block encodings that represent the rectangle, and write them
- // to the compressed buffer as necessary. Whether or not the blocks
- // are overwritten by zeros or just their indices are updated is up
- // to debate.
- SkFAIL("Not implemented!");
- }
-
- // Blit a pattern of pixels defined by a rectangle-clipped mask;
- // typically used for text.
- virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE {
- // This function is currently not implemented. It is not explicitly
- // required by the contract, but if at some time a code path runs into
- // this function (which is entirely possible), it needs to be implemented.
- //
- // TODO (krajcevski):
- // This function will be most easily implemented in the same way as
- // blitAntiRect above.
- SkFAIL("Not implemented!");
- }
-
- // If the blitter just sets a single value for each pixel, return the
- // bitmap it draws into, and assign value. If not, return NULL and ignore
- // the value parameter.
- virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE {
- return NULL;
- }
-
- /**
- * Compressed texture blitters only really work correctly if they get
- * four blocks at a time. That being said, this blitter tries it's best
- * to preserve semantics if blitAntiH doesn't get called in too many
- * weird ways...
- */
- virtual int requestRowsPreserved() const { return kR11_EACBlockSz; }
-
- protected:
- virtual void onNotifyFinished() { this->flushRuns(); }
-
- private:
- static const int kR11_EACBlockSz = 4;
- static const int kPixelsPerBlock = kR11_EACBlockSz * kR11_EACBlockSz;
-
- // The longest possible run of pixels that this blitter will receive.
- // This is initialized in the constructor to 0x7FFE, which is one less
- // than the largest positive 16-bit integer. We make sure that it's one
- // less for debugging purposes. We also don't make this variable static
- // in order to make sure that we can construct a valid pointer to it.
- const int16_t kLongestRun;
-
- // Usually used in conjunction with kLongestRun. This is initialized to
- // zero.
- const SkAlpha kZeroAlpha;
-
- // This is the information that we buffer whenever we're asked to blit
- // a row with this blitter.
- struct BufferedRun {
- const SkAlpha* fAlphas;
- const int16_t* fRuns;
- int fX, fY;
- } fBufferedRuns[kR11_EACBlockSz];
-
- // The next row (0-3) that we need to blit. This value should never exceed
- // the number of rows that we have (kR11_EACBlockSz)
- int fNextRun;
-
- // The width and height of the image that we're blitting
- const int fWidth;
- const int fHeight;
-
- // The R11 EAC buffer that we're blitting into. It is assumed that the buffer
- // is large enough to store a compressed image of size fWidth*fHeight.
- uint64_t* const fBuffer;
-
- // Various utility functions
- int blocksWide() const { return fWidth / kR11_EACBlockSz; }
- int blocksTall() const { return fHeight / kR11_EACBlockSz; }
- int totalBlocks() const { return (fWidth * fHeight) / kPixelsPerBlock; }
-
- // Returns the block index for the block containing pixel (x, y). Block
- // indices start at zero and proceed in raster order.
- int getBlockOffset(int x, int y) const {
- SkASSERT(x < fWidth);
- SkASSERT(y < fHeight);
- const int blockCol = x / kR11_EACBlockSz;
- const int blockRow = y / kR11_EACBlockSz;
- return blockRow * this->blocksWide() + blockCol;
- }
-
- // Returns a pointer to the block containing pixel (x, y)
- uint64_t *getBlock(int x, int y) const {
- return fBuffer + this->getBlockOffset(x, y);
- }
-
- // The following function writes the buffered runs to compressed blocks.
- // If fNextRun < 4, then we fill the runs that we haven't buffered with
- // the constant zero buffer.
- void flushRuns();
- };
+ // Returns the blitter for the given compression format. Note, the blitter
+ // is intended to be used with the proper input. I.e. if you try to blit
+ // RGB source data into an R11 EAC texture, you're gonna have a bad time.
+ SkBlitter* CreateBlitterForFormat(int width, int height, void* compressedBuffer,
+ Format format);
}
#endif