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// Copyright 2011 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.
// -----------------------------------------------------------------------------
// WebP encoder: main interface
// Author: Skal (
#include "./types.h"
#ifdef __cplusplus
extern "C" {
#define WEBP_ENCODER_ABI_VERSION 0x020e // 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 WebPImageHint WebPImageHint;
// typedef enum WebPEncCSP WebPEncCSP;
// typedef enum WebPPreset WebPPreset;
// typedef enum WebPEncodingError WebPEncodingError;
typedef struct WebPConfig WebPConfig;
typedef struct WebPPicture WebPPicture; // main structure for I/O
typedef struct WebPAuxStats WebPAuxStats;
typedef struct WebPMemoryWriter WebPMemoryWriter;
// Return the encoder's version number, packed in hexadecimal using 8bits for
// each of major/minor/revision. E.g: v2.5.7 is 0x020507.
WEBP_EXTERN int WebPGetEncoderVersion(void);
// One-stop-shop call! No questions asked:
// Returns the size of the compressed data (pointed to by *output), or 0 if
// an error occurred. The compressed data must be released by the caller
// using the call 'WebPFree(*output)'.
// These functions compress using the lossy format, and the quality_factor
// can go from 0 (smaller output, lower quality) to 100 (best quality,
// larger output).
WEBP_EXTERN size_t WebPEncodeRGB(const uint8_t* rgb,
int width, int height, int stride,
float quality_factor, uint8_t** output);
WEBP_EXTERN size_t WebPEncodeBGR(const uint8_t* bgr,
int width, int height, int stride,
float quality_factor, uint8_t** output);
WEBP_EXTERN size_t WebPEncodeRGBA(const uint8_t* rgba,
int width, int height, int stride,
float quality_factor, uint8_t** output);
WEBP_EXTERN size_t WebPEncodeBGRA(const uint8_t* bgra,
int width, int height, int stride,
float quality_factor, uint8_t** output);
// These functions are the equivalent of the above, but compressing in a
// lossless manner. Files are usually larger than lossy format, but will
// not suffer any compression loss.
WEBP_EXTERN size_t WebPEncodeLosslessRGB(const uint8_t* rgb,
int width, int height, int stride,
uint8_t** output);
WEBP_EXTERN size_t WebPEncodeLosslessBGR(const uint8_t* bgr,
int width, int height, int stride,
uint8_t** output);
WEBP_EXTERN size_t WebPEncodeLosslessRGBA(const uint8_t* rgba,
int width, int height, int stride,
uint8_t** output);
WEBP_EXTERN size_t WebPEncodeLosslessBGRA(const uint8_t* bgra,
int width, int height, int stride,
uint8_t** output);
// Releases memory returned by the WebPEncode*() functions above.
WEBP_EXTERN void WebPFree(void* ptr);
// Coding parameters
// Image characteristics hint for the underlying encoder.
typedef enum WebPImageHint {
WEBP_HINT_DEFAULT = 0, // default preset.
WEBP_HINT_PICTURE, // digital picture, like portrait, inner shot
WEBP_HINT_PHOTO, // outdoor photograph, with natural lighting
WEBP_HINT_GRAPH, // Discrete tone image (graph, map-tile etc).
} WebPImageHint;
// Compression parameters.
struct WebPConfig {
int lossless; // Lossless encoding (0=lossy(default), 1=lossless).
float quality; // between 0 and 100. For lossy, 0 gives the smallest
// size and 100 the largest. For lossless, this
// parameter is the amount of effort put into the
// compression: 0 is the fastest but gives larger
// files compared to the slowest, but best, 100.
int method; // quality/speed trade-off (0=fast, 6=slower-better)
WebPImageHint image_hint; // Hint for image type (lossless only for now).
int target_size; // if non-zero, set the desired target size in bytes.
// Takes precedence over the 'compression' parameter.
float target_PSNR; // if non-zero, specifies the minimal distortion to
// try to achieve. Takes precedence over target_size.
int segments; // maximum number of segments to use, in [1..4]
int sns_strength; // Spatial Noise Shaping. 0=off, 100=maximum.
int filter_strength; // range: [0 = off .. 100 = strongest]
int filter_sharpness; // range: [0 = off .. 7 = least sharp]
int filter_type; // filtering type: 0 = simple, 1 = strong (only used
// if filter_strength > 0 or autofilter > 0)
int autofilter; // Auto adjust filter's strength [0 = off, 1 = on]
int alpha_compression; // Algorithm for encoding the alpha plane (0 = none,
// 1 = compressed with WebP lossless). Default is 1.
int alpha_filtering; // Predictive filtering method for alpha plane.
// 0: none, 1: fast, 2: best. Default if 1.
int alpha_quality; // Between 0 (smallest size) and 100 (lossless).
// Default is 100.
int pass; // number of entropy-analysis passes (in [1..10]).
int show_compressed; // if true, export the compressed picture back.
// In-loop filtering is not applied.
int preprocessing; // preprocessing filter:
// 0=none, 1=segment-smooth, 2=pseudo-random dithering
int partitions; // log2(number of token partitions) in [0..3]. Default
// is set to 0 for easier progressive decoding.
int partition_limit; // quality degradation allowed to fit the 512k limit
// on prediction modes coding (0: no degradation,
// 100: maximum possible degradation).
int emulate_jpeg_size; // If true, compression parameters will be remapped
// to better match the expected output size from
// JPEG compression. Generally, the output size will
// be similar but the degradation will be lower.
int thread_level; // If non-zero, try and use multi-threaded encoding.
int low_memory; // If set, reduce memory usage (but increase CPU use).
int near_lossless; // Near lossless encoding [0 = max loss .. 100 = off
// (default)].
int exact; // if non-zero, preserve the exact RGB values under
// transparent area. Otherwise, discard this invisible
// RGB information for better compression. The default
// value is 0.
int use_delta_palette; // reserved for future lossless feature
int use_sharp_yuv; // if needed, use sharp (and slow) RGB->YUV conversion
uint32_t pad[2]; // padding for later use
// Enumerate some predefined settings for WebPConfig, depending on the type
// of source picture. These presets are used when calling WebPConfigPreset().
typedef enum WebPPreset {
WEBP_PRESET_DEFAULT = 0, // default preset.
WEBP_PRESET_PICTURE, // digital picture, like portrait, inner shot
WEBP_PRESET_PHOTO, // outdoor photograph, with natural lighting
WEBP_PRESET_DRAWING, // hand or line drawing, with high-contrast details
WEBP_PRESET_ICON, // small-sized colorful images
WEBP_PRESET_TEXT // text-like
} WebPPreset;
// Internal, version-checked, entry point
WEBP_EXTERN int WebPConfigInitInternal(WebPConfig*, WebPPreset, float, int);
// Should always be called, to initialize a fresh WebPConfig structure before
// modification. Returns false in case of version mismatch. WebPConfigInit()
// must have succeeded before using the 'config' object.
// Note that the default values are lossless=0 and quality=75.
static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
return WebPConfigInitInternal(config, WEBP_PRESET_DEFAULT, 75.f,
// This function will initialize the configuration according to a predefined
// set of parameters (referred to by 'preset') and a given quality factor.
// This function can be called as a replacement to WebPConfigInit(). Will
// return false in case of error.
static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
WebPPreset preset, float quality) {
return WebPConfigInitInternal(config, preset, quality,
// Activate the lossless compression mode with the desired efficiency level
// between 0 (fastest, lowest compression) and 9 (slower, best compression).
// A good default level is '6', providing a fair tradeoff between compression
// speed and final compressed size.
// This function will overwrite several fields from config: 'method', 'quality'
// and 'lossless'. Returns false in case of parameter error.
WEBP_EXTERN int WebPConfigLosslessPreset(WebPConfig* config, int level);
// Returns true if 'config' is non-NULL and all configuration parameters are
// within their valid ranges.
WEBP_EXTERN int WebPValidateConfig(const WebPConfig* config);
// Input / Output
// Structure for storing auxiliary statistics.
struct WebPAuxStats {
int coded_size; // final size
float PSNR[5]; // peak-signal-to-noise ratio for Y/U/V/All/Alpha
int block_count[3]; // number of intra4/intra16/skipped macroblocks
int header_bytes[2]; // approximate number of bytes spent for header
// and mode-partition #0
int residual_bytes[3][4]; // approximate number of bytes spent for
// DC/AC/uv coefficients for each (0..3) segments.
int segment_size[4]; // number of macroblocks in each segments
int segment_quant[4]; // quantizer values for each segments
int segment_level[4]; // filtering strength for each segments [0..63]
int alpha_data_size; // size of the transparency data
int layer_data_size; // size of the enhancement layer data
// lossless encoder statistics
uint32_t lossless_features; // bit0:predictor bit1:cross-color transform
// bit2:subtract-green bit3:color indexing
int histogram_bits; // number of precision bits of histogram
int transform_bits; // precision bits for transform
int cache_bits; // number of bits for color cache lookup
int palette_size; // number of color in palette, if used
int lossless_size; // final lossless size
int lossless_hdr_size; // lossless header (transform, huffman etc) size
int lossless_data_size; // lossless image data size
uint32_t pad[2]; // padding for later use
// Signature for output function. Should return true if writing was successful.
// data/data_size is the segment of data to write, and 'picture' is for
// reference (and so one can make use of picture->custom_ptr).
typedef int (*WebPWriterFunction)(const uint8_t* data, size_t data_size,
const WebPPicture* picture);
// WebPMemoryWrite: a special WebPWriterFunction that writes to memory using
// the following WebPMemoryWriter object (to be set as a custom_ptr).
struct WebPMemoryWriter {
uint8_t* mem; // final buffer (of size 'max_size', larger than 'size').
size_t size; // final size
size_t max_size; // total capacity
uint32_t pad[1]; // padding for later use
// The following must be called first before any use.
WEBP_EXTERN void WebPMemoryWriterInit(WebPMemoryWriter* writer);
// The following must be called to deallocate writer->mem memory. The 'writer'
// object itself is not deallocated.
WEBP_EXTERN void WebPMemoryWriterClear(WebPMemoryWriter* writer);
// The custom writer to be used with WebPMemoryWriter as custom_ptr. Upon
// completion, writer.mem and writer.size will hold the coded data.
// writer.mem must be freed by calling WebPMemoryWriterClear.
WEBP_EXTERN int WebPMemoryWrite(const uint8_t* data, size_t data_size,
const WebPPicture* picture);
// Progress hook, called from time to time to report progress. It can return
// false to request an abort of the encoding process, or true otherwise if
// everything is OK.
typedef int (*WebPProgressHook)(int percent, const WebPPicture* picture);
// Color spaces.
typedef enum WebPEncCSP {
// chroma sampling
WEBP_YUV420 = 0, // 4:2:0
WEBP_YUV420A = 4, // alpha channel variant
WEBP_CSP_UV_MASK = 3, // bit-mask to get the UV sampling factors
WEBP_CSP_ALPHA_BIT = 4 // bit that is set if alpha is present
} WebPEncCSP;
// Encoding error conditions.
typedef enum WebPEncodingError {
VP8_ENC_OK = 0,
VP8_ENC_ERROR_OUT_OF_MEMORY, // memory error allocating objects
VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY, // memory error while flushing bits
VP8_ENC_ERROR_NULL_PARAMETER, // a pointer parameter is NULL
VP8_ENC_ERROR_INVALID_CONFIGURATION, // configuration is invalid
VP8_ENC_ERROR_BAD_DIMENSION, // picture has invalid width/height
VP8_ENC_ERROR_PARTITION0_OVERFLOW, // partition is bigger than 512k
VP8_ENC_ERROR_PARTITION_OVERFLOW, // partition is bigger than 16M
VP8_ENC_ERROR_BAD_WRITE, // error while flushing bytes
VP8_ENC_ERROR_FILE_TOO_BIG, // file is bigger than 4G
VP8_ENC_ERROR_USER_ABORT, // abort request by user
VP8_ENC_ERROR_LAST // list terminator. always last.
} WebPEncodingError;
// maximum width/height allowed (inclusive), in pixels
#define WEBP_MAX_DIMENSION 16383
// Main exchange structure (input samples, output bytes, statistics)
struct WebPPicture {
// Main flag for encoder selecting between ARGB or YUV input.
// It is recommended to use ARGB input (*argb, argb_stride) for lossless
// compression, and YUV input (*y, *u, *v, etc.) for lossy compression
// since these are the respective native colorspace for these formats.
int use_argb;
// YUV input (mostly used for input to lossy compression)
WebPEncCSP colorspace; // colorspace: should be YUV420 for now (=Y'CbCr).
int width, height; // dimensions (less or equal to WEBP_MAX_DIMENSION)
uint8_t *y, *u, *v; // pointers to luma/chroma planes.
int y_stride, uv_stride; // luma/chroma strides.
uint8_t* a; // pointer to the alpha plane
int a_stride; // stride of the alpha plane
uint32_t pad1[2]; // padding for later use
// ARGB input (mostly used for input to lossless compression)
uint32_t* argb; // Pointer to argb (32 bit) plane.
int argb_stride; // This is stride in pixels units, not bytes.
uint32_t pad2[3]; // padding for later use
// Byte-emission hook, to store compressed bytes as they are ready.
WebPWriterFunction writer; // can be NULL
void* custom_ptr; // can be used by the writer.
// map for extra information (only for lossy compression mode)
int extra_info_type; // 1: intra type, 2: segment, 3: quant
// 4: intra-16 prediction mode,
// 5: chroma prediction mode,
// 6: bit cost, 7: distortion
uint8_t* extra_info; // if not NULL, points to an array of size
// ((width + 15) / 16) * ((height + 15) / 16) that
// will be filled with a macroblock map, depending
// on extra_info_type.
// Pointer to side statistics (updated only if not NULL)
WebPAuxStats* stats;
// Error code for the latest error encountered during encoding
WebPEncodingError error_code;
// If not NULL, report progress during encoding.
WebPProgressHook progress_hook;
void* user_data; // this field is free to be set to any value and
// used during callbacks (like progress-report e.g.).
uint32_t pad3[3]; // padding for later use
// Unused for now
uint8_t *pad4, *pad5;
uint32_t pad6[8]; // padding for later use
void* memory_; // row chunk of memory for yuva planes
void* memory_argb_; // and for argb too.
void* pad7[2]; // padding for later use
// Internal, version-checked, entry point
WEBP_EXTERN int WebPPictureInitInternal(WebPPicture*, int);
// Should always be called, to initialize the structure. Returns false in case
// of version mismatch. WebPPictureInit() must have succeeded before using the
// 'picture' object.
// Note that, by default, use_argb is false and colorspace is WEBP_YUV420.
static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
return WebPPictureInitInternal(picture, WEBP_ENCODER_ABI_VERSION);
// WebPPicture utils
// Convenience allocation / deallocation based on picture->width/height:
// Allocate y/u/v buffers as per colorspace/width/height specification.
// Note! This function will free the previous buffer if needed.
// Returns false in case of memory error.
WEBP_EXTERN int WebPPictureAlloc(WebPPicture* picture);
// Release the memory allocated by WebPPictureAlloc() or WebPPictureImport*().
// Note that this function does _not_ free the memory used by the 'picture'
// object itself.
// Besides memory (which is reclaimed) all other fields of 'picture' are
// preserved.
WEBP_EXTERN void WebPPictureFree(WebPPicture* picture);
// Copy the pixels of *src into *dst, using WebPPictureAlloc. Upon return, *dst
// will fully own the copied pixels (this is not a view). The 'dst' picture need
// not be initialized as its content is overwritten.
// Returns false in case of memory allocation error.
WEBP_EXTERN int WebPPictureCopy(const WebPPicture* src, WebPPicture* dst);
// Compute the single distortion for packed planes of samples.
// 'src' will be compared to 'ref', and the raw distortion stored into
// '*distortion'. The refined metric (log(MSE), log(1 - ssim),...' will be
// stored in '*result'.
// 'x_step' is the horizontal stride (in bytes) between samples.
// 'src/ref_stride' is the byte distance between rows.
// Returns false in case of error (bad parameter, memory allocation error, ...).
WEBP_EXTERN int WebPPlaneDistortion(const uint8_t* src, size_t src_stride,
const uint8_t* ref, size_t ref_stride,
int width, int height,
size_t x_step,
int type, // 0 = PSNR, 1 = SSIM, 2 = LSIM
float* distortion, float* result);
// Compute PSNR, SSIM or LSIM distortion metric between two pictures. Results
// are in dB, stored in result[] in the B/G/R/A/All order. The distortion is
// always performed using ARGB samples. Hence if the input is YUV(A), the
// picture will be internally converted to ARGB (just for the measurement).
// Warning: this function is rather CPU-intensive.
WEBP_EXTERN int WebPPictureDistortion(
const WebPPicture* src, const WebPPicture* ref,
int metric_type, // 0 = PSNR, 1 = SSIM, 2 = LSIM
float result[5]);
// self-crops a picture to the rectangle defined by top/left/width/height.
// Returns false in case of memory allocation error, or if the rectangle is
// outside of the source picture.
// The rectangle for the view is defined by the top-left corner pixel
// coordinates (left, top) as well as its width and height. This rectangle
// must be fully be comprised inside the 'src' source picture. If the source
// picture uses the YUV420 colorspace, the top and left coordinates will be
// snapped to even values.
WEBP_EXTERN int WebPPictureCrop(WebPPicture* picture,
int left, int top, int width, int height);
// Extracts a view from 'src' picture into 'dst'. The rectangle for the view
// is defined by the top-left corner pixel coordinates (left, top) as well
// as its width and height. This rectangle must be fully be comprised inside
// the 'src' source picture. If the source picture uses the YUV420 colorspace,
// the top and left coordinates will be snapped to even values.
// Picture 'src' must out-live 'dst' picture. Self-extraction of view is allowed
// ('src' equal to 'dst') as a mean of fast-cropping (but note that doing so,
// the original dimension will be lost). Picture 'dst' need not be initialized
// with WebPPictureInit() if it is different from 'src', since its content will
// be overwritten.
// Returns false in case of memory allocation error or invalid parameters.
WEBP_EXTERN int WebPPictureView(const WebPPicture* src,
int left, int top, int width, int height,
WebPPicture* dst);
// Returns true if the 'picture' is actually a view and therefore does
// not own the memory for pixels.
WEBP_EXTERN int WebPPictureIsView(const WebPPicture* picture);
// Rescale a picture to new dimension width x height.
// If either 'width' or 'height' (but not both) is 0 the corresponding
// dimension will be calculated preserving the aspect ratio.
// No gamma correction is applied.
// Returns false in case of error (invalid parameter or insufficient memory).
WEBP_EXTERN int WebPPictureRescale(WebPPicture* pic, int width, int height);
// Colorspace conversion function to import RGB samples.
// Previous buffer will be free'd, if any.
// *rgb buffer should have a size of at least height * rgb_stride.
// Returns false in case of memory error.
WEBP_EXTERN int WebPPictureImportRGB(
WebPPicture* picture, const uint8_t* rgb, int rgb_stride);
// Same, but for RGBA buffer.
WEBP_EXTERN int WebPPictureImportRGBA(
WebPPicture* picture, const uint8_t* rgba, int rgba_stride);
// Same, but for RGBA buffer. Imports the RGB direct from the 32-bit format
// input buffer ignoring the alpha channel. Avoids needing to copy the data
// to a temporary 24-bit RGB buffer to import the RGB only.
WEBP_EXTERN int WebPPictureImportRGBX(
WebPPicture* picture, const uint8_t* rgbx, int rgbx_stride);
// Variants of the above, but taking BGR(A|X) input.
WEBP_EXTERN int WebPPictureImportBGR(
WebPPicture* picture, const uint8_t* bgr, int bgr_stride);
WEBP_EXTERN int WebPPictureImportBGRA(
WebPPicture* picture, const uint8_t* bgra, int bgra_stride);
WEBP_EXTERN int WebPPictureImportBGRX(
WebPPicture* picture, const uint8_t* bgrx, int bgrx_stride);
// Converts picture->argb data to the YUV420A format. The 'colorspace'
// parameter is deprecated and should be equal to WEBP_YUV420.
// Upon return, picture->use_argb is set to false. The presence of real
// non-opaque transparent values is detected, and 'colorspace' will be
// adjusted accordingly. Note that this method is lossy.
// Returns false in case of error.
WEBP_EXTERN int WebPPictureARGBToYUVA(WebPPicture* picture,
WebPEncCSP /*colorspace = WEBP_YUV420*/);
// Same as WebPPictureARGBToYUVA(), but the conversion is done using
// pseudo-random dithering with a strength 'dithering' between
// 0.0 (no dithering) and 1.0 (maximum dithering). This is useful
// for photographic picture.
WEBP_EXTERN int WebPPictureARGBToYUVADithered(
WebPPicture* picture, WebPEncCSP colorspace, float dithering);
// Performs 'sharp' RGBA->YUVA420 downsampling and colorspace conversion.
// Downsampling is handled with extra care in case of color clipping. This
// method is roughly 2x slower than WebPPictureARGBToYUVA() but produces better
// and sharper YUV representation.
// Returns false in case of error.
WEBP_EXTERN int WebPPictureSharpARGBToYUVA(WebPPicture* picture);
// kept for backward compatibility:
WEBP_EXTERN int WebPPictureSmartARGBToYUVA(WebPPicture* picture);
// Converts picture->yuv to picture->argb and sets picture->use_argb to true.
// The input format must be YUV_420 or YUV_420A. The conversion from YUV420 to
// ARGB incurs a small loss too.
// Note that the use of this colorspace is discouraged if one has access to the
// raw ARGB samples, since using YUV420 is comparatively lossy.
// Returns false in case of error.
WEBP_EXTERN int WebPPictureYUVAToARGB(WebPPicture* picture);
// Helper function: given a width x height plane of RGBA or YUV(A) samples
// clean-up or smoothen the YUV or RGB samples under fully transparent area,
// to help compressibility (no guarantee, though).
WEBP_EXTERN void WebPCleanupTransparentArea(WebPPicture* picture);
// Scan the picture 'picture' for the presence of non fully opaque alpha values.
// Returns true in such case. Otherwise returns false (indicating that the
// alpha plane can be ignored altogether e.g.).
WEBP_EXTERN int WebPPictureHasTransparency(const WebPPicture* picture);
// Remove the transparency information (if present) by blending the color with
// the background color 'background_rgb' (specified as 24bit RGB triplet).
// After this call, all alpha values are reset to 0xff.
WEBP_EXTERN void WebPBlendAlpha(WebPPicture* pic, uint32_t background_rgb);
// Main call
// Main encoding call, after config and picture have been initialized.
// 'picture' must be less than 16384x16384 in dimension (cf WEBP_MAX_DIMENSION),
// and the 'config' object must be a valid one.
// Returns false in case of error, true otherwise.
// In case of error, picture->error_code is updated accordingly.
// 'picture' can hold the source samples in both YUV(A) or ARGB input, depending
// on the value of 'picture->use_argb'. It is highly recommended to use
// the former for lossy encoding, and the latter for lossless encoding
// (when config.lossless is true). Automatic conversion from one format to
// another is provided but they both incur some loss.
WEBP_EXTERN int WebPEncode(const WebPConfig* config, WebPPicture* picture);
#ifdef __cplusplus
} // extern "C"
#endif /* WEBP_WEBP_ENCODE_H_ */