mirror of
https://github.com/webmproject/libwebp.git
synced 2025-01-01 00:08:24 +01:00
48f827574e
The new modes are
MODE_rgbA
MODE_bgrA
MODE_Argb
MODE_rgbA_4444
It's binary incompatible, since the enums changed.
While at it, i removed the now unneeded KeepAlpha methods.
-> Saved ~12k of code!
* made explicit mention that alpha_plane is persistent,
so we have access to the full alpha plane data at all time.
Incremental decoding of alpha was planned for, but not
implemented. So better not dragged this constaint for now
and make the code easier until we revisit that.
Change-Id: Idaba281a6ca819965ca062d1c23329f36d90c7ff
115 lines
5.0 KiB
C
115 lines
5.0 KiB
C
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Internal header: WebP decoding parameters and custom IO on buffer
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//
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// Author: somnath@google.com (Somnath Banerjee)
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#ifndef WEBP_DEC_WEBPI_H_
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#define WEBP_DEC_WEBPI_H_
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#include "../utils/rescaler.h"
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#include "../webp/decode_vp8.h"
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//------------------------------------------------------------------------------
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// WebPDecParams: Decoding output parameters. Transient internal object.
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typedef struct WebPDecParams WebPDecParams;
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typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
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typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
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struct WebPDecParams {
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WebPDecBuffer* output; // output buffer.
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uint8_t* tmp_y, *tmp_u, *tmp_v; // cache for the fancy upsampler
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// or used for tmp rescaling
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int last_y; // coordinate of the line that was last output
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const WebPDecoderOptions* options; // if not NULL, use alt decoding features
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// rescalers
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WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
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void* memory; // overall scratch memory for the output work.
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OutputFunc emit; // output RGB or YUV samples
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OutputFunc emit_alpha; // output alpha channel
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OutputRowFunc emit_alpha_row; // output one line of rescaled alpha values
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};
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// Should be called first, before any use of the WebPDecParams object.
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void WebPResetDecParams(WebPDecParams* const params);
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//------------------------------------------------------------------------------
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// Header parsing helpers
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// Structure storing a description of the RIFF headers.
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typedef struct {
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const uint8_t* data; // input buffer
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size_t data_size; // input buffer size
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size_t offset; // offset to main data chunk (VP8 or VP8L)
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const uint8_t* alpha_data; // points to alpha chunk (if present)
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size_t alpha_data_size; // alpha chunk size
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size_t compressed_size; // VP8/VP8L compressed data size
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size_t riff_size; // size of the riff payload (or 0 if absent)
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int is_lossless; // true if a VP8L chunk is present
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} WebPHeaderStructure;
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// Skips over all valid chunks prior to the first VP8/VP8L frame header.
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// Returns VP8_STATUS_OK on success,
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// VP8_STATUS_BITSTREAM_ERROR if an invalid header/chunk is found, and
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// VP8_STATUS_NOT_ENOUGH_DATA if case of insufficient data.
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// In 'headers', compressed_size, offset, alpha_data, alpha_size and lossless
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// fields are updated appropriately upon success.
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VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
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//------------------------------------------------------------------------------
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// Misc utils
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// Initializes VP8Io with custom setup, io and teardown functions. The default
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// hooks will use the supplied 'params' as io->opaque handle.
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void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
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// Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
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// to the *compressed* format, not the output one.
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int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
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VP8Io* const io, WEBP_CSP_MODE src_colorspace);
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//------------------------------------------------------------------------------
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// Internal functions regarding WebPDecBuffer memory (in buffer.c).
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// Don't really need to be externally visible for now.
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// Prepare 'buffer' with the requested initial dimensions width/height.
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// If no external storage is supplied, initializes buffer by allocating output
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// memory and setting up the stride information. Validate the parameters. Return
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// an error code in case of problem (no memory, or invalid stride / size /
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// dimension / etc.). If *options is not NULL, also verify that the options'
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// parameters are valid and apply them to the width/height dimensions of the
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// output buffer. This takes cropping / scaling / rotation into account.
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VP8StatusCode WebPAllocateDecBuffer(int width, int height,
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const WebPDecoderOptions* const options,
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WebPDecBuffer* const buffer);
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// Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
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// memory (still held by 'src').
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void WebPCopyDecBuffer(const WebPDecBuffer* const src,
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WebPDecBuffer* const dst);
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// Copy and transfer ownership from src to dst (beware of parameter order!)
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void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif /* WEBP_DEC_WEBPI_H_ */
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