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_DEC_H_ 15 #define WEBP_DEC_WEBPI_DEC_H_ 16 17 #ifdef __cplusplus 18 extern "C" { 19 #endif 20 21 #include "src/utils/rescaler_utils.h" 22 #include "src/dec/vp8_dec.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 (*OutputAlphaFunc)(const VP8Io* const io, WebPDecParams* const p, 30 int expected_num_out_lines); 31 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos, 32 int max_out_lines); 33 34 struct WebPDecParams { 35 WebPDecBuffer* output; // output buffer. 36 uint8_t* tmp_y, *tmp_u, *tmp_v; // cache for the fancy upsampler 37 // or used for tmp rescaling 38 39 int last_y; // coordinate of the line that was last output 40 const WebPDecoderOptions* options; // if not NULL, use alt decoding features 41 42 WebPRescaler* scaler_y, *scaler_u, *scaler_v, *scaler_a; // rescalers 43 void* memory; // overall scratch memory for the output work. 44 45 OutputFunc emit; // output RGB or YUV samples 46 OutputAlphaFunc emit_alpha; // output alpha channel 47 OutputRowFunc emit_alpha_row; // output one line of rescaled alpha values 48 }; 49 50 // Should be called first, before any use of the WebPDecParams object. 51 void WebPResetDecParams(WebPDecParams* const params); 52 53 //------------------------------------------------------------------------------ 54 // Header parsing helpers 55 56 // Structure storing a description of the RIFF headers. 57 typedef struct { 58 const uint8_t* data; // input buffer 59 size_t data_size; // input buffer size 60 int have_all_data; // true if all data is known to be available 61 size_t offset; // offset to main data chunk (VP8 or VP8L) 62 const uint8_t* alpha_data; // points to alpha chunk (if present) 63 size_t alpha_data_size; // alpha chunk size 64 size_t compressed_size; // VP8/VP8L compressed data size 65 size_t riff_size; // size of the riff payload (or 0 if absent) 66 int is_lossless; // true if a VP8L chunk is present 67 } WebPHeaderStructure; 68 69 // Skips over all valid chunks prior to the first VP8/VP8L frame header. 70 // Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk), 71 // VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE 72 // in the case of non-decodable features (animation for instance). 73 // In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless 74 // fields are updated appropriately upon success. 75 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers); 76 77 //------------------------------------------------------------------------------ 78 // Misc utils 79 80 // Initializes VP8Io with custom setup, io and teardown functions. The default 81 // hooks will use the supplied 'params' as io->opaque handle. 82 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io); 83 84 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers 85 // to the *compressed* format, not the output one. 86 int WebPIoInitFromOptions(const WebPDecoderOptions* const options, 87 VP8Io* const io, WEBP_CSP_MODE src_colorspace); 88 89 //------------------------------------------------------------------------------ 90 // Internal functions regarding WebPDecBuffer memory (in buffer.c). 91 // Don't really need to be externally visible for now. 92 93 // Prepare 'buffer' with the requested initial dimensions width/height. 94 // If no external storage is supplied, initializes buffer by allocating output 95 // memory and setting up the stride information. Validate the parameters. Return 96 // an error code in case of problem (no memory, or invalid stride / size / 97 // dimension / etc.). If *options is not NULL, also verify that the options' 98 // parameters are valid and apply them to the width/height dimensions of the 99 // output buffer. This takes cropping / scaling / rotation into account. 100 // Also incorporates the options->flip flag to flip the buffer parameters if 101 // needed. 102 VP8StatusCode WebPAllocateDecBuffer(int width, int height, 103 const WebPDecoderOptions* const options, 104 WebPDecBuffer* const buffer); 105 106 // Flip buffer vertically by negating the various strides. 107 VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer); 108 109 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the 110 // memory (still held by 'src'). No pixels are copied. 111 void WebPCopyDecBuffer(const WebPDecBuffer* const src, 112 WebPDecBuffer* const dst); 113 114 // Copy and transfer ownership from src to dst (beware of parameter order!) 115 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst); 116 117 // Copy pixels from 'src' into a *preallocated* 'dst' buffer. Returns 118 // VP8_STATUS_INVALID_PARAM if the 'dst' is not set up correctly for the copy. 119 VP8StatusCode WebPCopyDecBufferPixels(const WebPDecBuffer* const src, 120 WebPDecBuffer* const dst); 121 122 // Returns true if decoding will be slow with the current configuration 123 // and bitstream features. 124 int WebPAvoidSlowMemory(const WebPDecBuffer* const output, 125 const WebPBitstreamFeatures* const features); 126 127 //------------------------------------------------------------------------------ 128 129 #ifdef __cplusplus 130 } // extern "C" 131 #endif 132 133 #endif /* WEBP_DEC_WEBPI_DEC_H_ */ 134
