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 (at) google.com (Somnath Banerjee) 13 14 #ifndef WEBP_DEC_WEBPI_H_ 15 #define WEBP_DEC_WEBPI_H_ 16 17 #if defined(__cplusplus) || defined(c_plusplus) 18 extern "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 27 typedef struct WebPDecParams WebPDecParams; 28 typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p); 29 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos); 30 31 struct 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. 48 void WebPResetDecParams(WebPDecParams* const params); 49 50 //------------------------------------------------------------------------------ 51 // Header parsing helpers 52 53 // Structure storing a description of the RIFF headers. 54 typedef struct { 55 const uint8_t* data; // input buffer 56 size_t data_size; // input buffer size 57 size_t offset; // offset to main data chunk (VP8 or VP8L) 58 const uint8_t* alpha_data; // points to alpha chunk (if present) 59 size_t alpha_data_size; // alpha chunk size 60 size_t compressed_size; // VP8/VP8L compressed data size 61 size_t riff_size; // size of the riff payload (or 0 if absent) 62 int is_lossless; // true if a VP8L chunk is present 63 } WebPHeaderStructure; 64 65 // Skips over all valid chunks prior to the first VP8/VP8L frame header. 66 // Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk), 67 // VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE 68 // in the case of non-decodable features (animation for instance). 69 // In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless 70 // fields are updated appropriately upon success. 71 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers); 72 73 //------------------------------------------------------------------------------ 74 // Misc utils 75 76 // Initializes VP8Io with custom setup, io and teardown functions. The default 77 // hooks will use the supplied 'params' as io->opaque handle. 78 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io); 79 80 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers 81 // to the *compressed* format, not the output one. 82 int WebPIoInitFromOptions(const WebPDecoderOptions* const options, 83 VP8Io* const io, WEBP_CSP_MODE src_colorspace); 84 85 //------------------------------------------------------------------------------ 86 // Internal functions regarding WebPDecBuffer memory (in buffer.c). 87 // Don't really need to be externally visible for now. 88 89 // Prepare 'buffer' with the requested initial dimensions width/height. 90 // If no external storage is supplied, initializes buffer by allocating output 91 // memory and setting up the stride information. Validate the parameters. Return 92 // an error code in case of problem (no memory, or invalid stride / size / 93 // dimension / etc.). If *options is not NULL, also verify that the options' 94 // parameters are valid and apply them to the width/height dimensions of the 95 // output buffer. This takes cropping / scaling / rotation into account. 96 VP8StatusCode WebPAllocateDecBuffer(int width, int height, 97 const WebPDecoderOptions* const options, 98 WebPDecBuffer* const buffer); 99 100 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the 101 // memory (still held by 'src'). 102 void WebPCopyDecBuffer(const WebPDecBuffer* const src, 103 WebPDecBuffer* const dst); 104 105 // Copy and transfer ownership from src to dst (beware of parameter order!) 106 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst); 107 108 109 110 //------------------------------------------------------------------------------ 111 112 #if defined(__cplusplus) || defined(c_plusplus) 113 } // extern "C" 114 #endif 115 116 #endif /* WEBP_DEC_WEBPI_H_ */ 117
