143 lines
6.5 KiB
C++
143 lines
6.5 KiB
C++
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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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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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "../utils/rescaler.h"
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#include "./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 (*OutputAlphaFunc)(const VP8Io* const io, WebPDecParams* const p,
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int expected_num_out_lines);
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typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos,
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int max_out_lines);
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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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OutputAlphaFunc emit_alpha; // output alpha channel
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OutputRowFunc emit_alpha_row; // output one line of rescaled alpha values
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WebPDecBuffer* final_output; // In case the user supplied a slow-memory
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// output, we decode image in temporary buffer
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// (this::output) and copy it here.
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WebPDecBuffer tmp_buffer; // this::output will point to this one in case
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// of slow memory.
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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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// Delete all memory (after an error occurred, for instance)
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void WebPFreeDecParams(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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int have_all_data; // true if all data is known to be available
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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, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk),
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// VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE
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// in the case of non-decodable features (animation for instance).
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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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// Also incorporates the options->flip flag to flip the buffer parameters if
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// needed.
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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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// Flip buffer vertically by negating the various strides.
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VP8StatusCode WebPFlipBuffer(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'). No pixels are copied.
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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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// Copy pixels from 'src' into a *preallocated* 'dst' buffer. Returns
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// VP8_STATUS_INVALID_PARAM if the 'dst' is not set up correctly for the copy.
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VP8StatusCode WebPCopyDecBufferPixels(const WebPDecBuffer* const src,
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WebPDecBuffer* const dst);
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// Returns true if decoding will be slow with the current configuration
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// and bitstream features.
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int WebPAvoidSlowMemory(const WebPDecBuffer* const output,
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const WebPBitstreamFeatures* const features);
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//------------------------------------------------------------------------------
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif /* WEBP_DEC_WEBPI_H_ */
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