chromium/third_party/libwebp/src/src/enc/filter_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.
// -----------------------------------------------------------------------------
//
// Selecting filter level
//
// Author: [email protected] (Somnath Banerjee)

#include <assert.h>
#include "src/enc/vp8i_enc.h"
#include "src/dsp/dsp.h"

// This table gives, for a given sharpness, the filtering strength to be
// used (at least) in order to filter a given edge step delta.
// This is constructed by brute force inspection: for all delta, we iterate
// over all possible filtering strength / thresh until needs_filter() returns
// true.
#define MAX_DELTA_SIZE …
static const uint8_t kLevelsFromDelta[8][MAX_DELTA_SIZE] = …;

int VP8FilterStrengthFromDelta(int sharpness, int delta) { … }

//------------------------------------------------------------------------------
// Paragraph 15.4: compute the inner-edge filtering strength

#if !defined(WEBP_REDUCE_SIZE)

static int GetILevel(int sharpness, int level) {
  if (sharpness > 0) {
    if (sharpness > 4) {
      level >>= 2;
    } else {
      level >>= 1;
    }
    if (level > 9 - sharpness) {
      level = 9 - sharpness;
    }
  }
  if (level < 1) level = 1;
  return level;
}

static void DoFilter(const VP8EncIterator* const it, int level) {
  const VP8Encoder* const enc = it->enc_;
  const int ilevel = GetILevel(enc->config_->filter_sharpness, level);
  const int limit = 2 * level + ilevel;

  uint8_t* const y_dst = it->yuv_out2_ + Y_OFF_ENC;
  uint8_t* const u_dst = it->yuv_out2_ + U_OFF_ENC;
  uint8_t* const v_dst = it->yuv_out2_ + V_OFF_ENC;

  // copy current block to yuv_out2_
  memcpy(y_dst, it->yuv_out_, YUV_SIZE_ENC * sizeof(uint8_t));

  if (enc->filter_hdr_.simple_ == 1) {   // simple
    VP8SimpleHFilter16i(y_dst, BPS, limit);
    VP8SimpleVFilter16i(y_dst, BPS, limit);
  } else {    // complex
    const int hev_thresh = (level >= 40) ? 2 : (level >= 15) ? 1 : 0;
    VP8HFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
    VP8HFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
    VP8VFilter16i(y_dst, BPS, limit, ilevel, hev_thresh);
    VP8VFilter8i(u_dst, v_dst, BPS, limit, ilevel, hev_thresh);
  }
}

//------------------------------------------------------------------------------
// SSIM metric for one macroblock

static double GetMBSSIM(const uint8_t* yuv1, const uint8_t* yuv2) {
  int x, y;
  double sum = 0.;

  // compute SSIM in a 10 x 10 window
  for (y = VP8_SSIM_KERNEL; y < 16 - VP8_SSIM_KERNEL; y++) {
    for (x = VP8_SSIM_KERNEL; x < 16 - VP8_SSIM_KERNEL; x++) {
      sum += VP8SSIMGetClipped(yuv1 + Y_OFF_ENC, BPS, yuv2 + Y_OFF_ENC, BPS,
                               x, y, 16, 16);
    }
  }
  for (x = 1; x < 7; x++) {
    for (y = 1; y < 7; y++) {
      sum += VP8SSIMGetClipped(yuv1 + U_OFF_ENC, BPS, yuv2 + U_OFF_ENC, BPS,
                               x, y, 8, 8);
      sum += VP8SSIMGetClipped(yuv1 + V_OFF_ENC, BPS, yuv2 + V_OFF_ENC, BPS,
                               x, y, 8, 8);
    }
  }
  return sum;
}

#endif  // !defined(WEBP_REDUCE_SIZE)

//------------------------------------------------------------------------------
// Exposed APIs: Encoder should call the following 3 functions to adjust
// loop filter strength

void VP8InitFilter(VP8EncIterator* const it) { … }

void VP8StoreFilterStats(VP8EncIterator* const it) { … }

void VP8AdjustFilterStrength(VP8EncIterator* const it) { … }

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