Blame src/dsp/filters.c

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// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Spatial prediction using various filters
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//
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// Author: Urvang (urvang@google.com)
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#include "src/dsp/dsp.h"
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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//------------------------------------------------------------------------------
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// Helpful macro.
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# define SANITY_CHECK(in, out)                                                 \
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  assert((in) != NULL);                                                        \
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  assert((out) != NULL);                                                       \
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  assert(width > 0);                                                           \
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  assert(height > 0);                                                          \
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  assert(stride >= width);                                                     \
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  assert(row >= 0 && num_rows > 0 && row + num_rows <= height);                \
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  (void)height;  // Silence unused warning.
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#if !WEBP_NEON_OMIT_C_CODE
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static WEBP_INLINE void PredictLine_C(const uint8_t* src, const uint8_t* pred,
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                                      uint8_t* dst, int length, int inverse) {
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  int i;
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  if (inverse) {
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    for (i = 0; i < length; ++i) dst[i] = src[i] + pred[i];
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  } else {
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    for (i = 0; i < length; ++i) dst[i] = src[i] - pred[i];
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  }
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}
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//------------------------------------------------------------------------------
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// Horizontal filter.
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static WEBP_INLINE void DoHorizontalFilter_C(const uint8_t* in,
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                                             int width, int height, int stride,
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                                             int row, int num_rows,
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                                             int inverse, uint8_t* out) {
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  const uint8_t* preds;
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  const size_t start_offset = row * stride;
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  const int last_row = row + num_rows;
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  SANITY_CHECK(in, out);
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  in += start_offset;
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  out += start_offset;
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  preds = inverse ? out : in;
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  if (row == 0) {
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    // Leftmost pixel is the same as input for topmost scanline.
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    out[0] = in[0];
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    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
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    row = 1;
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    preds += stride;
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    in += stride;
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    out += stride;
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  }
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  // Filter line-by-line.
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  while (row < last_row) {
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    // Leftmost pixel is predicted from above.
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    PredictLine_C(in, preds - stride, out, 1, inverse);
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    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
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    ++row;
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    preds += stride;
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    in += stride;
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    out += stride;
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  }
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}
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//------------------------------------------------------------------------------
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// Vertical filter.
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static WEBP_INLINE void DoVerticalFilter_C(const uint8_t* in,
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                                           int width, int height, int stride,
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                                           int row, int num_rows,
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                                           int inverse, uint8_t* out) {
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  const uint8_t* preds;
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  const size_t start_offset = row * stride;
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  const int last_row = row + num_rows;
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  SANITY_CHECK(in, out);
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  in += start_offset;
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  out += start_offset;
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  preds = inverse ? out : in;
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  if (row == 0) {
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    // Very first top-left pixel is copied.
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    out[0] = in[0];
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    // Rest of top scan-line is left-predicted.
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    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
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    row = 1;
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    in += stride;
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    out += stride;
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  } else {
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    // We are starting from in-between. Make sure 'preds' points to prev row.
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    preds -= stride;
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  }
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  // Filter line-by-line.
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  while (row < last_row) {
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    PredictLine_C(in, preds, out, width, inverse);
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    ++row;
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    preds += stride;
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    in += stride;
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    out += stride;
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  }
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}
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#endif  // !WEBP_NEON_OMIT_C_CODE
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//------------------------------------------------------------------------------
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// Gradient filter.
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static WEBP_INLINE int GradientPredictor_C(uint8_t a, uint8_t b, uint8_t c) {
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  const int g = a + b - c;
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  return ((g & ~0xff) == 0) ? g : (g < 0) ? 0 : 255;  // clip to 8bit
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}
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#if !WEBP_NEON_OMIT_C_CODE
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static WEBP_INLINE void DoGradientFilter_C(const uint8_t* in,
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                                           int width, int height, int stride,
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                                           int row, int num_rows,
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                                           int inverse, uint8_t* out) {
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  const uint8_t* preds;
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  const size_t start_offset = row * stride;
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  const int last_row = row + num_rows;
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  SANITY_CHECK(in, out);
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  in += start_offset;
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  out += start_offset;
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  preds = inverse ? out : in;
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  // left prediction for top scan-line
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  if (row == 0) {
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    out[0] = in[0];
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    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
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    row = 1;
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    preds += stride;
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    in += stride;
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    out += stride;
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  }
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  // Filter line-by-line.
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  while (row < last_row) {
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    int w;
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    // leftmost pixel: predict from above.
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    PredictLine_C(in, preds - stride, out, 1, inverse);
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    for (w = 1; w < width; ++w) {
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      const int pred = GradientPredictor_C(preds[w - 1],
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                                           preds[w - stride],
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                                           preds[w - stride - 1]);
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      out[w] = in[w] + (inverse ? pred : -pred);
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    }
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    ++row;
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    preds += stride;
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    in += stride;
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    out += stride;
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  }
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}
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#endif  // !WEBP_NEON_OMIT_C_CODE
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#undef SANITY_CHECK
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//------------------------------------------------------------------------------
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#if !WEBP_NEON_OMIT_C_CODE
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static void HorizontalFilter_C(const uint8_t* data, int width, int height,
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                               int stride, uint8_t* filtered_data) {
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  DoHorizontalFilter_C(data, width, height, stride, 0, height, 0,
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                       filtered_data);
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}
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static void VerticalFilter_C(const uint8_t* data, int width, int height,
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                             int stride, uint8_t* filtered_data) {
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  DoVerticalFilter_C(data, width, height, stride, 0, height, 0, filtered_data);
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}
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static void GradientFilter_C(const uint8_t* data, int width, int height,
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                             int stride, uint8_t* filtered_data) {
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  DoGradientFilter_C(data, width, height, stride, 0, height, 0, filtered_data);
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}
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#endif  // !WEBP_NEON_OMIT_C_CODE
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//------------------------------------------------------------------------------
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static void HorizontalUnfilter_C(const uint8_t* prev, const uint8_t* in,
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                                 uint8_t* out, int width) {
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  uint8_t pred = (prev == NULL) ? 0 : prev[0];
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  int i;
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  for (i = 0; i < width; ++i) {
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    out[i] = pred + in[i];
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    pred = out[i];
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  }
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}
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#if !WEBP_NEON_OMIT_C_CODE
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static void VerticalUnfilter_C(const uint8_t* prev, const uint8_t* in,
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                               uint8_t* out, int width) {
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  if (prev == NULL) {
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    HorizontalUnfilter_C(NULL, in, out, width);
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  } else {
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    int i;
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    for (i = 0; i < width; ++i) out[i] = prev[i] + in[i];
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  }
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}
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#endif  // !WEBP_NEON_OMIT_C_CODE
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static void GradientUnfilter_C(const uint8_t* prev, const uint8_t* in,
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                               uint8_t* out, int width) {
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  if (prev == NULL) {
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    HorizontalUnfilter_C(NULL, in, out, width);
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  } else {
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    uint8_t top = prev[0], top_left = top, left = top;
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    int i;
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    for (i = 0; i < width; ++i) {
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      top = prev[i];  // need to read this first, in case prev==out
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      left = in[i] + GradientPredictor_C(left, top, top_left);
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      top_left = top;
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      out[i] = left;
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    }
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  }
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}
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//------------------------------------------------------------------------------
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// Init function
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WebPFilterFunc WebPFilters[WEBP_FILTER_LAST];
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WebPUnfilterFunc WebPUnfilters[WEBP_FILTER_LAST];
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extern void VP8FiltersInitMIPSdspR2(void);
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extern void VP8FiltersInitMSA(void);
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extern void VP8FiltersInitNEON(void);
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extern void VP8FiltersInitSSE2(void);
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WEBP_DSP_INIT_FUNC(VP8FiltersInit) {
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  WebPUnfilters[WEBP_FILTER_NONE] = NULL;
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#if !WEBP_NEON_OMIT_C_CODE
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  WebPUnfilters[WEBP_FILTER_HORIZONTAL] = HorizontalUnfilter_C;
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  WebPUnfilters[WEBP_FILTER_VERTICAL] = VerticalUnfilter_C;
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#endif
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  WebPUnfilters[WEBP_FILTER_GRADIENT] = GradientUnfilter_C;
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  WebPFilters[WEBP_FILTER_NONE] = NULL;
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#if !WEBP_NEON_OMIT_C_CODE
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  WebPFilters[WEBP_FILTER_HORIZONTAL] = HorizontalFilter_C;
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  WebPFilters[WEBP_FILTER_VERTICAL] = VerticalFilter_C;
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  WebPFilters[WEBP_FILTER_GRADIENT] = GradientFilter_C;
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#endif
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  if (VP8GetCPUInfo != NULL) {
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#if defined(WEBP_USE_SSE2)
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    if (VP8GetCPUInfo(kSSE2)) {
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      VP8FiltersInitSSE2();
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    }
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#endif
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#if defined(WEBP_USE_MIPS_DSP_R2)
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    if (VP8GetCPUInfo(kMIPSdspR2)) {
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      VP8FiltersInitMIPSdspR2();
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    }
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#endif
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#if defined(WEBP_USE_MSA)
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    if (VP8GetCPUInfo(kMSA)) {
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      VP8FiltersInitMSA();
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    }
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#endif
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  }
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#if defined(WEBP_USE_NEON)
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  if (WEBP_NEON_OMIT_C_CODE ||
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      (VP8GetCPUInfo != NULL && VP8GetCPUInfo(kNEON))) {
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    VP8FiltersInitNEON();
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  }
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#endif
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  assert(WebPUnfilters[WEBP_FILTER_HORIZONTAL] != NULL);
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  assert(WebPUnfilters[WEBP_FILTER_VERTICAL] != NULL);
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  assert(WebPUnfilters[WEBP_FILTER_GRADIENT] != NULL);
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  assert(WebPFilters[WEBP_FILTER_HORIZONTAL] != NULL);
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  assert(WebPFilters[WEBP_FILTER_VERTICAL] != NULL);
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  assert(WebPFilters[WEBP_FILTER_GRADIENT] != NULL);
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}