1// Copyright 2011 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// Internal header: WebP decoding parameters and custom IO on buffer
11//
12// Author: somnath@google.com (Somnath Banerjee)
13
14#ifndef WEBP_DEC_WEBPI_H_
15#define WEBP_DEC_WEBPI_H_
16
17#ifdef __cplusplus
18extern "C" {
19#endif
20
21#include "../utils/rescaler.h"
22#include "./decode_vp8.h"
23
24//------------------------------------------------------------------------------
25// WebPDecParams: Decoding output parameters. Transient internal object.
26
27typedef struct WebPDecParams WebPDecParams;
28typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
29typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
30
31struct WebPDecParams {
32  WebPDecBuffer* output;             // output buffer.
33  uint8_t* tmp_y, *tmp_u, *tmp_v;    // cache for the fancy upsampler
34                                     // or used for tmp rescaling
35
36  int last_y;                 // coordinate of the line that was last output
37  const WebPDecoderOptions* options;  // if not NULL, use alt decoding features
38  // rescalers
39  WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
40  void* memory;                  // overall scratch memory for the output work.
41
42  OutputFunc emit;               // output RGB or YUV samples
43  OutputFunc emit_alpha;         // output alpha channel
44  OutputRowFunc emit_alpha_row;  // output one line of rescaled alpha values
45};
46
47// Should be called first, before any use of the WebPDecParams object.
48void WebPResetDecParams(WebPDecParams* const params);
49
50//------------------------------------------------------------------------------
51// Header parsing helpers
52
53// Structure storing a description of the RIFF headers.
54typedef struct {
55  const uint8_t* data;         // input buffer
56  size_t data_size;            // input buffer size
57  int have_all_data;           // true if all data is known to be available
58  size_t offset;               // offset to main data chunk (VP8 or VP8L)
59  const uint8_t* alpha_data;   // points to alpha chunk (if present)
60  size_t alpha_data_size;      // alpha chunk size
61  size_t compressed_size;      // VP8/VP8L compressed data size
62  size_t riff_size;            // size of the riff payload (or 0 if absent)
63  int is_lossless;             // true if a VP8L chunk is present
64} WebPHeaderStructure;
65
66// Skips over all valid chunks prior to the first VP8/VP8L frame header.
67// Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk),
68// VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE
69// in the case of non-decodable features (animation for instance).
70// In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless
71// fields are updated appropriately upon success.
72VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
73
74//------------------------------------------------------------------------------
75// Misc utils
76
77// Initializes VP8Io with custom setup, io and teardown functions. The default
78// hooks will use the supplied 'params' as io->opaque handle.
79void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
80
81// Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
82// to the *compressed* format, not the output one.
83int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
84                          VP8Io* const io, WEBP_CSP_MODE src_colorspace);
85
86//------------------------------------------------------------------------------
87// Internal functions regarding WebPDecBuffer memory (in buffer.c).
88// Don't really need to be externally visible for now.
89
90// Prepare 'buffer' with the requested initial dimensions width/height.
91// If no external storage is supplied, initializes buffer by allocating output
92// memory and setting up the stride information. Validate the parameters. Return
93// an error code in case of problem (no memory, or invalid stride / size /
94// dimension / etc.). If *options is not NULL, also verify that the options'
95// parameters are valid and apply them to the width/height dimensions of the
96// output buffer. This takes cropping / scaling / rotation into account.
97// Also incorporates the options->flip flag to flip the buffer parameters if
98// needed.
99VP8StatusCode WebPAllocateDecBuffer(int width, int height,
100                                    const WebPDecoderOptions* const options,
101                                    WebPDecBuffer* const buffer);
102
103// Flip buffer vertically by negating the various strides.
104VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer);
105
106// Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
107// memory (still held by 'src').
108void WebPCopyDecBuffer(const WebPDecBuffer* const src,
109                       WebPDecBuffer* const dst);
110
111// Copy and transfer ownership from src to dst (beware of parameter order!)
112void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
113
114//------------------------------------------------------------------------------
115
116#ifdef __cplusplus
117}    // extern "C"
118#endif
119
120#endif  /* WEBP_DEC_WEBPI_H_ */
121