1 // Copyright 2011 Google Inc. All Rights Reserved.
3 // This code is licensed under the same terms as WebM:
4 // Software License Agreement: http://www.webmproject.org/license/software/
5 // Additional IP Rights Grant: http://www.webmproject.org/license/additional/
6 // -----------------------------------------------------------------------------
8 // Internal header: WebP decoding parameters and custom IO on buffer
10 // Author: somnath@google.com (Somnath Banerjee)
12 #ifndef WEBP_DEC_WEBPI_H_
13 #define WEBP_DEC_WEBPI_H_
15 #if defined(__cplusplus) || defined(c_plusplus)
19 #include "../utils/rescaler.h"
20 #include "./decode_vp8.h"
22 //------------------------------------------------------------------------------
23 // WebPDecParams: Decoding output parameters. Transient internal object.
25 typedef struct WebPDecParams WebPDecParams;
26 typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
27 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
29 struct WebPDecParams {
30 WebPDecBuffer* output; // output buffer.
31 uint8_t* tmp_y, *tmp_u, *tmp_v; // cache for the fancy upsampler
32 // or used for tmp rescaling
34 int last_y; // coordinate of the line that was last output
35 const WebPDecoderOptions* options; // if not NULL, use alt decoding features
37 WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
38 void* memory; // overall scratch memory for the output work.
40 OutputFunc emit; // output RGB or YUV samples
41 OutputFunc emit_alpha; // output alpha channel
42 OutputRowFunc emit_alpha_row; // output one line of rescaled alpha values
45 // Should be called first, before any use of the WebPDecParams object.
46 void WebPResetDecParams(WebPDecParams* const params);
48 //------------------------------------------------------------------------------
49 // Header parsing helpers
51 // Structure storing a description of the RIFF headers.
53 const uint8_t* data; // input buffer
54 size_t data_size; // input buffer size
55 size_t offset; // offset to main data chunk (VP8 or VP8L)
56 const uint8_t* alpha_data; // points to alpha chunk (if present)
57 size_t alpha_data_size; // alpha chunk size
58 size_t compressed_size; // VP8/VP8L compressed data size
59 size_t riff_size; // size of the riff payload (or 0 if absent)
60 int is_lossless; // true if a VP8L chunk is present
61 } WebPHeaderStructure;
63 // Skips over all valid chunks prior to the first VP8/VP8L frame header.
64 // Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk),
65 // VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE
66 // in the case of non-decodable features (animation for instance).
67 // In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless
68 // fields are updated appropriately upon success.
69 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
71 //------------------------------------------------------------------------------
74 // Initializes VP8Io with custom setup, io and teardown functions. The default
75 // hooks will use the supplied 'params' as io->opaque handle.
76 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
78 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
79 // to the *compressed* format, not the output one.
80 int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
81 VP8Io* const io, WEBP_CSP_MODE src_colorspace);
83 //------------------------------------------------------------------------------
84 // Internal functions regarding WebPDecBuffer memory (in buffer.c).
85 // Don't really need to be externally visible for now.
87 // Prepare 'buffer' with the requested initial dimensions width/height.
88 // If no external storage is supplied, initializes buffer by allocating output
89 // memory and setting up the stride information. Validate the parameters. Return
90 // an error code in case of problem (no memory, or invalid stride / size /
91 // dimension / etc.). If *options is not NULL, also verify that the options'
92 // parameters are valid and apply them to the width/height dimensions of the
93 // output buffer. This takes cropping / scaling / rotation into account.
94 VP8StatusCode WebPAllocateDecBuffer(int width, int height,
95 const WebPDecoderOptions* const options,
96 WebPDecBuffer* const buffer);
98 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
99 // memory (still held by 'src').
100 void WebPCopyDecBuffer(const WebPDecBuffer* const src,
101 WebPDecBuffer* const dst);
103 // Copy and transfer ownership from src to dst (beware of parameter order!)
104 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
108 //------------------------------------------------------------------------------
110 #if defined(__cplusplus) || defined(c_plusplus)
114 #endif /* WEBP_DEC_WEBPI_H_ */