📝 Editando: decode.h

// Copyright 2010 Google Inc. All Rights Reserved. // // Use of this source code is governed by a BSD-style license // that can be found in the COPYING file in the root of the source // tree. An additional intellectual property rights grant can be found // in the file PATENTS. All contributing project authors may // be found in the AUTHORS file in the root of the source tree. // ----------------------------------------------------------------------------- // // Main decoding functions for WebP images. // // Author: Skal (pascal.massimino@gmail.com) #ifndef WEBP_WEBP_DECODE_H_ #define WEBP_WEBP_DECODE_H_ #include "./types.h" #ifdef __cplusplus extern "C" { #endif #define WEBP_DECODER_ABI_VERSION 0x0208 // MAJOR(8b) + MINOR(8b) // Note: forward declaring enumerations is not allowed in (strict) C and C++, // the types are left here for reference. // typedef enum VP8StatusCode VP8StatusCode; // typedef enum WEBP_CSP_MODE WEBP_CSP_MODE; typedef struct WebPRGBABuffer WebPRGBABuffer; typedef struct WebPYUVABuffer WebPYUVABuffer; typedef struct WebPDecBuffer WebPDecBuffer; typedef struct WebPIDecoder WebPIDecoder; typedef struct WebPBitstreamFeatures WebPBitstreamFeatures; typedef struct WebPDecoderOptions WebPDecoderOptions; typedef struct WebPDecoderConfig WebPDecoderConfig; // Return the decoder's version number, packed in hexadecimal using 8bits for // each of major/minor/revision. E.g: v2.5.7 is 0x020507. WEBP_EXTERN int WebPGetDecoderVersion(void); // Retrieve basic header information: width, height. // This function will also validate the header, returning true on success, // false otherwise. '*width' and '*height' are only valid on successful return. // Pointers 'width' and 'height' can be passed NULL if deemed irrelevant. WEBP_EXTERN int WebPGetInfo(const uint8_t* data, size_t data_size, int* width, int* height); // Decodes WebP images pointed to by 'data' and returns RGBA samples, along // with the dimensions in *width and *height. The ordering of samples in // memory is R, G, B, A, R, G, B, A... in scan order (endian-independent). // The returned pointer should be deleted calling WebPFree(). // Returns NULL in case of error. WEBP_EXTERN uint8_t* WebPDecodeRGBA(const uint8_t* data, size_t data_size, int* width, int* height); // Same as WebPDecodeRGBA, but returning A, R, G, B, A, R, G, B... ordered data. WEBP_EXTERN uint8_t* WebPDecodeARGB(const uint8_t* data, size_t data_size, int* width, int* height); // Same as WebPDecodeRGBA, but returning B, G, R, A, B, G, R, A... ordered data. WEBP_EXTERN uint8_t* WebPDecodeBGRA(const uint8_t* data, size_t data_size, int* width, int* height); // Same as WebPDecodeRGBA, but returning R, G, B, R, G, B... ordered data. // If the bitstream contains transparency, it is ignored. WEBP_EXTERN uint8_t* WebPDecodeRGB(const uint8_t* data, size_t data_size, int* width, int* height); // Same as WebPDecodeRGB, but returning B, G, R, B, G, R... ordered data. WEBP_EXTERN uint8_t* WebPDecodeBGR(const uint8_t* data, size_t data_size, int* width, int* height); // Decode WebP images pointed to by 'data' to Y'UV format(*). The pointer // returned is the Y samples buffer. Upon return, *u and *v will point to // the U and V chroma data. These U and V buffers need NOT be passed to // WebPFree(), unlike the returned Y luma one. The dimension of the U and V // planes are both (*width + 1) / 2 and (*height + 1)/ 2. // Upon return, the Y buffer has a stride returned as '*stride', while U and V // have a common stride returned as '*uv_stride'. // Return NULL in case of error. // (*) Also named Y'CbCr. See: http://en.wikipedia.org/wiki/YCbCr WEBP_EXTERN uint8_t* WebPDecodeYUV(const uint8_t* data, size_t data_size, int* width, int* height, uint8_t** u, uint8_t** v, int* stride, int* uv_stride); // Releases memory returned by the WebPDecode*() functions above. WEBP_EXTERN void WebPFree(void* ptr); // These five functions are variants of the above ones, that decode the image // directly into a pre-allocated buffer 'output_buffer'. The maximum storage // available in this buffer is indicated by 'output_buffer_size'. If this // storage is not sufficient (or an error occurred), NULL is returned. // Otherwise, output_buffer is returned, for convenience. // The parameter 'output_stride' specifies the distance (in bytes) // between scanlines. Hence, output_buffer_size is expected to be at least // output_stride x picture-height. WEBP_EXTERN uint8_t* WebPDecodeRGBAInto( const uint8_t* data, size_t data_size, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); WEBP_EXTERN uint8_t* WebPDecodeARGBInto( const uint8_t* data, size_t data_size, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); WEBP_EXTERN uint8_t* WebPDecodeBGRAInto( const uint8_t* data, size_t data_size, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); // RGB and BGR variants. Here too the transparency information, if present, // will be dropped and ignored. WEBP_EXTERN uint8_t* WebPDecodeRGBInto( const uint8_t* data, size_t data_size, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); WEBP_EXTERN uint8_t* WebPDecodeBGRInto( const uint8_t* data, size_t data_size, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); // WebPDecodeYUVInto() is a variant of WebPDecodeYUV() that operates directly // into pre-allocated luma/chroma plane buffers. This function requires the // strides to be passed: one for the luma plane and one for each of the // chroma ones. The size of each plane buffer is passed as 'luma_size', // 'u_size' and 'v_size' respectively. // Pointer to the luma plane ('*luma') is returned or NULL if an error occurred // during decoding (or because some buffers were found to be too small). WEBP_EXTERN uint8_t* WebPDecodeYUVInto( const uint8_t* data, size_t data_size, uint8_t* luma, size_t luma_size, int luma_stride, uint8_t* u, size_t u_size, int u_stride, uint8_t* v, size_t v_size, int v_stride); //------------------------------------------------------------------------------ // Output colorspaces and buffer // Colorspaces // Note: the naming describes the byte-ordering of packed samples in memory. // For instance, MODE_BGRA relates to samples ordered as B,G,R,A,B,G,R,A,... // Non-capital names (e.g.:MODE_Argb) relates to pre-multiplied RGB channels. // RGBA-4444 and RGB-565 colorspaces are represented by following byte-order: // RGBA-4444: [r3 r2 r1 r0 g3 g2 g1 g0], [b3 b2 b1 b0 a3 a2 a1 a0], ... // RGB-565: [r4 r3 r2 r1 r0 g5 g4 g3], [g2 g1 g0 b4 b3 b2 b1 b0], ... // In the case WEBP_SWAP_16BITS_CSP is defined, the bytes are swapped for // these two modes: // RGBA-4444: [b3 b2 b1 b0 a3 a2 a1 a0], [r3 r2 r1 r0 g3 g2 g1 g0], ... // RGB-565: [g2 g1 g0 b4 b3 b2 b1 b0], [r4 r3 r2 r1 r0 g5 g4 g3], ... typedef enum WEBP_CSP_MODE { MODE_RGB = 0, MODE_RGBA = 1, MODE_BGR = 2, MODE_BGRA = 3, MODE_ARGB = 4, MODE_RGBA_4444 = 5, MODE_RGB_565 = 6, // RGB-premultiplied transparent modes (alpha value is preserved) MODE_rgbA = 7, MODE_bgrA = 8, MODE_Argb = 9, MODE_rgbA_4444 = 10, // YUV modes must come after RGB ones. MODE_YUV = 11, MODE_YUVA = 12, // yuv 4:2:0 MODE_LAST = 13 } WEBP_CSP_MODE; // Some useful macros: static WEBP_INLINE int WebPIsPremultipliedMode(WEBP_CSP_MODE mode) { return (mode == MODE_rgbA || mode == MODE_bgrA || mode == MODE_Argb || mode == MODE_rgbA_4444); } static WEBP_INLINE int WebPIsAlphaMode(WEBP_CSP_MODE mode) { return (mode == MODE_RGBA || mode == MODE_BGRA || mode == MODE_ARGB || mode == MODE_RGBA_4444 || mode == MODE_YUVA || WebPIsPremultipliedMode(mode)); } static WEBP_INLINE int WebPIsRGBMode(WEBP_CSP_MODE mode) { return (mode < MODE_YUV); } //------------------------------------------------------------------------------ // WebPDecBuffer: Generic structure for describing the output sample buffer. struct WebPRGBABuffer { // view as RGBA uint8_t* rgba; // pointer to RGBA samples int stride; // stride in bytes from one scanline to the next. size_t size; // total size of the *rgba buffer. }; struct WebPYUVABuffer { // view as YUVA uint8_t* y, *u, *v, *a; // pointer to luma, chroma U/V, alpha samples int y_stride; // luma stride int u_stride, v_stride; // chroma strides int a_stride; // alpha stride size_t y_size; // luma plane size size_t u_size, v_size; // chroma planes size size_t a_size; // alpha-plane size }; // Output buffer struct WebPDecBuffer { WEBP_CSP_MODE colorspace; // Colorspace. int width, height; // Dimensions. int is_external_memory; // If non-zero, 'internal_memory' pointer is not // used. If value is '2' or more, the external // memory is considered 'slow' and multiple // read/write will be avoided. union { WebPRGBABuffer RGBA; WebPYUVABuffer YUVA; } u; // Nameless union of buffer parameters. uint32_t pad[4]; // padding for later use uint8_t* private_memory; // Internally allocated memory (only when // is_external_memory is 0). Should not be used // externally, but accessed via the buffer union. }; // Internal, version-checked, entry point WEBP_EXTERN int WebPInitDecBufferInternal(WebPDecBuffer*, int); // Initialize the structure as empty. Must be called before any other use. // Returns false in case of version mismatch static WEBP_INLINE int WebPInitDecBuffer(WebPDecBuffer* buffer) { return WebPInitDecBufferInternal(buffer, WEBP_DECODER_ABI_VERSION); } // Free any memory associated with the buffer. Must always be called last. // Note: doesn't free the 'buffer' structure itself. WEBP_EXTERN void WebPFreeDecBuffer(WebPDecBuffer* buffer); //------------------------------------------------------------------------------ // Enumeration of the status codes typedef enum VP8StatusCode { VP8_STATUS_OK = 0, VP8_STATUS_OUT_OF_MEMORY, VP8_STATUS_INVALID_PARAM, VP8_STATUS_BITSTREAM_ERROR, VP8_STATUS_UNSUPPORTED_FEATURE, VP8_STATUS_SUSPENDED, VP8_STATUS_USER_ABORT, VP8_STATUS_NOT_ENOUGH_DATA } VP8StatusCode; //------------------------------------------------------------------------------ // Incremental decoding // // This API allows streamlined decoding of partial data. // Picture can be incrementally decoded as data become available thanks to the // WebPIDecoder object. This object can be left in a SUSPENDED state if the // picture is only partially decoded, pending additional input. // Code example: // // WebPInitDecBuffer(&output_buffer); // output_buffer.colorspace = mode; // ... // WebPIDecoder* idec = WebPINewDecoder(&output_buffer); // while (additional_data_is_available) { // // ... (get additional data in some new_data[] buffer) // status = WebPIAppend(idec, new_data, new_data_size); // if (status != VP8_STATUS_OK && status != VP8_STATUS_SUSPENDED) { // break; // an error occurred. // } // // // The above call decodes the current available buffer. // // Part of the image can now be refreshed by calling // // WebPIDecGetRGB()/WebPIDecGetYUVA() etc. // } // WebPIDelete(idec); // Creates a new incremental decoder with the supplied buffer parameter. // This output_buffer can be passed NULL, in which case a default output buffer // is used (with MODE_RGB). Otherwise, an internal reference to 'output_buffer' // is kept, which means that the lifespan of 'output_buffer' must be larger than // that of the returned WebPIDecoder object. // The supplied 'output_buffer' content MUST NOT be changed between calls to // WebPIAppend() or WebPIUpdate() unless 'output_buffer.is_external_memory' is // not set to 0. In such a case, it is allowed to modify the pointers, size and // stride of output_buffer.u.RGBA or output_buffer.u.YUVA, provided they remain // within valid bounds. // All other fields of WebPDecBuffer MUST remain constant between calls. // Returns NULL if the allocation failed. WEBP_EXTERN WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer); // This function allocates and initializes an incremental-decoder object, which // will output the RGB/A samples specified by 'csp' into a preallocated // buffer 'output_buffer'. The size of this buffer is at least // 'output_buffer_size' and the stride (distance in bytes between two scanlines) // is specified by 'output_stride'. // Additionally, output_buffer can be passed NULL in which case the output // buffer will be allocated automatically when the decoding starts. The // colorspace 'csp' is taken into account for allocating this buffer. All other // parameters are ignored. // Returns NULL if the allocation failed, or if some parameters are invalid. WEBP_EXTERN WebPIDecoder* WebPINewRGB( WEBP_CSP_MODE csp, uint8_t* output_buffer, size_t output_buffer_size, int output_stride); // This function allocates and initializes an incremental-decoder object, which // will output the raw luma/chroma samples into a preallocated planes if // supplied. The luma plane is specified by its pointer 'luma', its size // 'luma_size' and its stride 'luma_stride'. Similarly, the chroma-u plane // is specified by the 'u', 'u_size' and 'u_stride' parameters, and the chroma-v // plane by 'v' and 'v_size'. And same for the alpha-plane. The 'a' pointer // can be pass NULL in case one is not interested in the transparency plane. // Conversely, 'luma' can be passed NULL if no preallocated planes are supplied. // In this case, the output buffer will be automatically allocated (using // MODE_YUVA) when decoding starts. All parameters are then ignored. // Returns NULL if the allocation failed or if a parameter is invalid. WEBP_EXTERN WebPIDecoder* WebPINewYUVA( uint8_t* luma, size_t luma_size, int luma_stride, uint8_t* u, size_t u_size, int u_stride, uint8_t* v, size_t v_size, int v_stride, uint8_t* a, size_t a_size, int a_stride); // Deprecated version of the above, without the alpha plane. // Kept for backward compatibility. WEBP_EXTERN WebPIDecoder* WebPINewYUV( uint8_t* luma, size_t luma_size, int luma_stride, uint8_t* u, size_t u_size, int u_stride, uint8_t* v, size_t v_size, int v_stride); // Deletes the WebPIDecoder object and associated memory. Must always be called // if WebPINewDecoder, WebPINewRGB or WebPINewYUV succeeded. WEBP_EXTERN void WebPIDelete(WebPIDecoder* idec); // Copies and decodes the next available data. Returns VP8_STATUS_OK when // the image is successfully decoded. Returns VP8_STATUS_SUSPENDED when more // data is expected. Returns error in other cases. WEBP_EXTERN VP8StatusCode WebPIAppend( WebPIDecoder* idec, const uint8_t* data, size_t data_size); // A variant of the above function to be used when data buffer contains // partial data from the beginning. In this case data buffer is not copied // to the internal memory. // Note that the value of the 'data' pointer can change between calls to // WebPIUpdate, for instance when the data buffer is resized to fit larger data. WEBP_EXTERN VP8StatusCode WebPIUpdate( WebPIDecoder* idec, const uint8_t* data, size_t data_size); // Returns the RGB/A image decoded so far. Returns NULL if output params // are not initialized yet. The RGB/A output type corresponds to the colorspace // specified during call to WebPINewDecoder() or WebPINewRGB(). // *last_y is the index of last decoded row in raster scan order. Some pointers // (*last_y, *width etc.) can be NULL if corresponding information is not // needed. The values in these pointers are only valid on successful (non-NULL) // return. WEBP_EXTERN uint8_t* WebPIDecGetRGB( const WebPIDecoder* idec, int* last_y, int* width, int* height, int* stride); // Same as above function to get a YUVA image. Returns pointer to the luma // plane or NULL in case of error. If there is no alpha information // the alpha pointer '*a' will be returned NULL. WEBP_EXTERN uint8_t* WebPIDecGetYUVA( const WebPIDecoder* idec, int* last_y, uint8_t** u, uint8_t** v, uint8_t** a, int* width, int* height, int* stride, int* uv_stride, int* a_stride); // Deprecated alpha-less version of WebPIDecGetYUVA(): it will ignore the // alpha information (if present). Kept for backward compatibility. static WEBP_INLINE uint8_t* WebPIDecGetYUV( const WebPIDecoder* idec, int* last_y, uint8_t** u, uint8_t** v, int* width, int* height, int* stride, int* uv_stride) { return WebPIDecGetYUVA(idec, last_y, u, v, NULL, width, height, stride, uv_stride, NULL); } // Generic call to retrieve information about the displayable area. // If non NULL, the left/right/width/height pointers are filled with the visible // rectangular area so far. // Returns NULL in case the incremental decoder object is in an invalid state. // Otherwise returns the pointer to the internal representation. This structure // is read-only, tied to WebPIDecoder's lifespan and should not be modified. WEBP_EXTERN const WebPDecBuffer* WebPIDecodedArea( const WebPIDecoder* idec, int* left, int* top, int* width, int* height); //------------------------------------------------------------------------------ // Advanced decoding parametrization // // Code sample for using the advanced decoding API /* // A) Init a configuration object WebPDecoderConfig config; CHECK(WebPInitDecoderConfig(&config)); // B) optional: retrieve the bitstream's features. CHECK(WebPGetFeatures(data, data_size, &config.input) == VP8_STATUS_OK); // C) Adjust 'config', if needed config.no_fancy_upsampling = 1; config.output.colorspace = MODE_BGRA; // etc. // Note that you can also make config.output point to an externally // supplied memory buffer, provided it's big enough to store the decoded // picture. Otherwise, config.output will just be used to allocate memory // and store the decoded picture. // D) Decode! CHECK(WebPDecode(data, data_size, &config) == VP8_STATUS_OK); // E) Decoded image is now in config.output (and config.output.u.RGBA) // F) Reclaim memory allocated in config's object. It's safe to call // this function even if the memory is external and wasn't allocated // by WebPDecode(). WebPFreeDecBuffer(&config.output); */ // Features gathered from the bitstream struct WebPBitstreamFeatures { int width; // Width in pixels, as read from the bitstream. int height; // Height in pixels, as read from the bitstream. int has_alpha; // True if the bitstream contains an alpha channel. int has_animation; // True if the bitstream is an animation. int format; // 0 = undefined (/mixed), 1 = lossy, 2 = lossless uint32_t pad[5]; // padding for later use }; // Internal, version-checked, entry point WEBP_EXTERN VP8StatusCode WebPGetFeaturesInternal( const uint8_t*, size_t, WebPBitstreamFeatures*, int); // Retrieve features from the bitstream. The *features structure is filled // with information gathered from the bitstream. // Returns VP8_STATUS_OK when the features are successfully retrieved. Returns // VP8_STATUS_NOT_ENOUGH_DATA when more data is needed to retrieve the // features from headers. Returns error in other cases. static WEBP_INLINE VP8StatusCode WebPGetFeatures( const uint8_t* data, size_t data_size, WebPBitstreamFeatures* features) { return WebPGetFeaturesInternal(data, data_size, features, WEBP_DECODER_ABI_VERSION); } // Decoding options struct WebPDecoderOptions { int bypass_filtering; // if true, skip the in-loop filtering int no_fancy_upsampling; // if true, use faster pointwise upsampler int use_cropping; // if true, cropping is applied _first_ int crop_left, crop_top; // top-left position for cropping. // Will be snapped to even values. int crop_width, crop_height; // dimension of the cropping area int use_scaling; // if true, scaling is applied _afterward_ int scaled_width, scaled_height; // final resolution int use_threads; // if true, use multi-threaded decoding int dithering_strength; // dithering strength (0=Off, 100=full) int flip; // flip output vertically int alpha_dithering_strength; // alpha dithering strength in [0..100] uint32_t pad[5]; // padding for later use }; // Main object storing the configuration for advanced decoding. struct WebPDecoderConfig { WebPBitstreamFeatures input; // Immutable bitstream features (optional) WebPDecBuffer output; // Output buffer (can point to external mem) WebPDecoderOptions options; // Decoding options }; // Internal, version-checked, entry point WEBP_EXTERN int WebPInitDecoderConfigInternal(WebPDecoderConfig*, int); // Initialize the configuration as empty. This function must always be // called first, unless WebPGetFeatures() is to be called. // Returns false in case of mismatched version. static WEBP_INLINE int WebPInitDecoderConfig(WebPDecoderConfig* config) { return WebPInitDecoderConfigInternal(config, WEBP_DECODER_ABI_VERSION); } // Instantiate a new incremental decoder object with the requested // configuration. The bitstream can be passed using 'data' and 'data_size' // parameter, in which case the features will be parsed and stored into // config->input. Otherwise, 'data' can be NULL and no parsing will occur. // Note that 'config' can be NULL too, in which case a default configuration // is used. If 'config' is not NULL, it must outlive the WebPIDecoder object // as some references to its fields will be used. No internal copy of 'config' // is made. // The return WebPIDecoder object must always be deleted calling WebPIDelete(). // Returns NULL in case of error (and config->status will then reflect // the error condition, if available). WEBP_EXTERN WebPIDecoder* WebPIDecode(const uint8_t* data, size_t data_size, WebPDecoderConfig* config); // Non-incremental version. This version decodes the full data at once, taking // 'config' into account. Returns decoding status (which should be VP8_STATUS_OK // if the decoding was successful). Note that 'config' cannot be NULL. WEBP_EXTERN VP8StatusCode WebPDecode(const uint8_t* data, size_t data_size, WebPDecoderConfig* config); #ifdef __cplusplus } // extern "C" #endif #endif /* WEBP_WEBP_DECODE_H_ */
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