godot/thirdparty/libwebp/src/enc/alpha_enc.c

// 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.
// -----------------------------------------------------------------------------
//
// Alpha-plane compression.
//
// Author: Skal ([email protected])

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#include "src/enc/vp8i_enc.h"
#include "src/dsp/dsp.h"
#include "src/utils/filters_utils.h"
#include "src/utils/quant_levels_utils.h"
#include "src/utils/utils.h"
#include "src/webp/encode.h"
#include "src/webp/format_constants.h"

// -----------------------------------------------------------------------------
// Encodes the given alpha data via specified compression method 'method'.
// The pre-processing (quantization) is performed if 'quality' is less than 100.
// For such cases, the encoding is lossy. The valid range is [0, 100] for
// 'quality' and [0, 1] for 'method':
//   'method = 0' - No compression;
//   'method = 1' - Use lossless coder on the alpha plane only
// 'filter' values [0, 4] correspond to prediction modes none, horizontal,
// vertical & gradient filters. The prediction mode 4 will try all the
// prediction modes 0 to 3 and pick the best one.
// 'effort_level': specifies how much effort must be spent to try and reduce
//  the compressed output size. In range 0 (quick) to 6 (slow).
//
// 'output' corresponds to the buffer containing compressed alpha data.
//          This buffer is allocated by this method and caller should call
//          WebPSafeFree(*output) when done.
// 'output_size' corresponds to size of this compressed alpha buffer.
//
// Returns 1 on successfully encoding the alpha and
//         0 if either:
//           invalid quality or method, or
//           memory allocation for the compressed data fails.

#include "src/enc/vp8li_enc.h"

static int EncodeLossless(const uint8_t* const data, int width, int height,
                          int effort_level,  // in [0..6] range
                          int use_quality_100, VP8LBitWriter* const bw,
                          WebPAuxStats* const stats) { … }

// -----------------------------------------------------------------------------

// Small struct to hold the result of a filter mode compression attempt.
FilterTrial;

// This function always returns an initialized 'bw' object, even upon error.
static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
                               int method, int filter, int reduce_levels,
                               int effort_level,  // in [0..6] range
                               uint8_t* const tmp_alpha,
                               FilterTrial* result) { … }

// -----------------------------------------------------------------------------

static int GetNumColors(const uint8_t* data, int width, int height,
                        int stride) { … }

#define FILTER_TRY_NONE …
#define FILTER_TRY_ALL …

// Given the input 'filter' option, return an OR'd bit-set of filters to try.
static uint32_t GetFilterMap(const uint8_t* alpha, int width, int height,
                             int filter, int effort_level) { … }

static void InitFilterTrial(FilterTrial* const score) { … }

static int ApplyFiltersAndEncode(const uint8_t* alpha, int width, int height,
                                 size_t data_size, int method, int filter,
                                 int reduce_levels, int effort_level,
                                 uint8_t** const output,
                                 size_t* const output_size,
                                 WebPAuxStats* const stats) { … }

static int EncodeAlpha(VP8Encoder* const enc,
                       int quality, int method, int filter,
                       int effort_level,
                       uint8_t** const output, size_t* const output_size) { … }

//------------------------------------------------------------------------------
// Main calls

static int CompressAlphaJob(void* arg1, void* unused) { … }

void VP8EncInitAlpha(VP8Encoder* const enc) { … }

int VP8EncStartAlpha(VP8Encoder* const enc) { … }

int VP8EncFinishAlpha(VP8Encoder* const enc) { … }

int VP8EncDeleteAlpha(VP8Encoder* const enc) { … }