libwebp/src/webp/decode.h

// Copyright 2010 Google Inc. All Rights Reserved.
//
// This code is licensed under the same terms as WebM:
//  Software License Agreement:  http://www.webmproject.org/license/software/
//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
//  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"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#define WEBP_DECODER_ABI_VERSION 0x0100    // MAJOR(8b) + MINOR(8b)

// 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 and return 0 in
// case of formatting error.
// Pointers *width/*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 RGB samples, along
// with the dimensions in *width and *height. The ordering of samples in
// memory is R, G, B, R, G, B... in scan order (endian-independent).
// The returned pointer should be deleted calling free().
// Returns NULL in case of error.
WEBP_EXTERN(uint8_t*) WebPDecodeRGB(const uint8_t* data, size_t data_size,
                                    int* width, int* height);

// Same as WebPDecodeRGB, but returning R, G, B, A, R, G, B, A... ordered data.
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 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);

// Same as WebPDecodeBGR, 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);

// Decode WEBP images stored in *data in 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 free()'d, 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);

// 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*) 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*) 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);
// BGR variants
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);
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);

// 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.
// RGB-565 and RGBA-4444 are also endian-agnostic and byte-oriented.
typedef enum { 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 sample buffer.

typedef struct {    // 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.
} WebPRGBABuffer;

typedef struct {              // 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
} WebPYUVABuffer;

// Output buffer
typedef struct {
  WEBP_CSP_MODE colorspace;  // Colorspace.
  int width, height;         // Dimensions.
  int is_external_memory;    // If true, 'internal_memory' pointer is not used.
  union {
    WebPRGBABuffer RGBA;
    WebPYUVABuffer YUVA;
  } u;                       // Nameless union of buffer parameters.
  uint8_t* private_memory;   // Internally allocated memory (only when
                             // is_external_memory is false). Should not be used
                             // externally, but accessed via the buffer union.
} WebPDecBuffer;

// 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 {
  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(&buffer);
//   buffer.colorspace = mode;
//   ...
//   WebPIDecoder* const idec = WebPINewDecoder(&buffer);
//   while (has_more_data) {
//     // ... (get additional data)
//     status = WebPIAppend(idec, new_data, new_data_size);
//     if (status != VP8_STATUS_SUSPENDED ||
//       break;
//     }
//
//     // The above call decodes the current available buffer.
//     // Part of the image can now be refreshed by calling to
//     // WebPIDecGetRGB()/WebPIDecGetYUV() etc.
//   }
//   WebPIDelete(idec);

typedef struct WebPIDecoder WebPIDecoder;

// 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.
// 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 r/g/b(/a) samples specified by 'mode' 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'. Returns NULL if the allocation failed.
WEBP_EXTERN(WebPIDecoder*) WebPINewRGB(
    WEBP_CSP_MODE mode,
    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. 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', 'v_size'
// and 'v_size'.
// Returns NULL if the allocation failed.
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 r/g/b/(a) image decoded so far. Returns NULL if output params
// are not initialized yet. The r/g/b/(a) output type corresponds to the mode
// specified in WebPINewDecoder()/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.
WEBP_EXTERN(uint8_t*) WebPIDecGetRGB(
    const WebPIDecoder* idec, int* last_y,
    int* width, int* height, int* stride);

// Same as above function to get YUV image. Returns pointer to the luma plane
// or NULL in case of error.
WEBP_EXTERN(uint8_t*) WebPIDecGetYUV(
    const WebPIDecoder* idec, int* last_y,
    uint8_t** u, uint8_t** v,
    int* width, int* height, int* stride, int* uv_stride);

// 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 = 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
typedef struct {
  int width;        // the original width, as read from the bitstream
  int height;       // the original height, as read from the bitstream
  int has_alpha;    // true if bitstream contains an alpha channel
  int no_incremental_decoding;  // if true, using incremental decoding is not
                                // recommended.
  int rotate;                   // TODO(later)
  int uv_sampling;              // should be 0 for now. TODO(later)
  int bitstream_version;        // should be 0 for now. TODO(later)
} WebPBitstreamFeatures;

// 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 false in case of error or version mismatch.
// In case of error, features->bitstream_status will reflect the error code.
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
typedef struct {
  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 force_rotation;                 // forced rotation (to be applied _last_)
  int no_enhancement;                 // if true, discard enhancement layer
  int use_threads;                    // if true, use multi-threaded decoding
} WebPDecoderOptions;

// Main object storing the configuration for advanced decoding.
typedef struct {
  WebPBitstreamFeatures input;  // Immutable bitstream features (optional)
  WebPDecBuffer output;         // Output buffer (can point to external mem)
  WebPDecoderOptions options;   // Decoding options
} WebPDecoderConfig;

// 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 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 now parsing will occur.
// Note that 'config' can be NULL too, in which case a default configuration is
// used.
// 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).
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. Return decoding status (VP8_STATUS_OK if decoding
// was successful).
WEBP_EXTERN(VP8StatusCode) WebPDecode(const uint8_t* data, size_t data_size,
                                      WebPDecoderConfig* config);

#if defined(__cplusplus) || defined(c_plusplus)
}    // extern "C"
#endif

#endif  /* WEBP_WEBP_DECODE_H_ */