third_party/libyuv/source/scale.c

/*
 *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE 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.
 */

#include "libyuv/scale.h"

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

#include "libyuv/planar_functions.h"  // For CopyPlane
#include "libyuv/row.h"
#include "libyuv/scale_row.h"

static __inline int Abs(int v) {
  return v >= 0 ? v : -v;
}

#define SUBSAMPLE(v, a, s) (v < 0) ? (-((-v + a) >> s)) : ((v + a) >> s)
#define CENTERSTART(dx, s) (dx < 0) ? -((-dx >> 1) + s) : ((dx >> 1) + s)

#define MIN1(x) ((x) < 1 ? 1 : (x))

static __inline uint32_t SumPixels(int iboxwidth, const uint16_t* src_ptr) {
  uint32_t sum = 0u;
  int x;
  assert(iboxwidth > 0);
  for (x = 0; x < iboxwidth; ++x) {
    sum += src_ptr[x];
  }
  return sum;
}

static __inline uint32_t SumPixels_16(int iboxwidth, const uint32_t* src_ptr) {
  uint32_t sum = 0u;
  int x;
  assert(iboxwidth > 0);
  for (x = 0; x < iboxwidth; ++x) {
    sum += src_ptr[x];
  }
  return sum;
}

static void ScaleAddCols2_C(int dst_width,
                            int boxheight,
                            int x,
                            int dx,
                            const uint16_t* src_ptr,
                            uint8_t* dst_ptr) {
  int i;
  int scaletbl[2];
  int minboxwidth = dx >> 16;
  int boxwidth;
  scaletbl[0] = 65536 / (MIN1(minboxwidth) * boxheight);
  scaletbl[1] = 65536 / (MIN1(minboxwidth + 1) * boxheight);
  for (i = 0; i < dst_width; ++i) {
    int ix = x >> 16;
    x += dx;
    boxwidth = MIN1((x >> 16) - ix);
    int scaletbl_index = boxwidth - minboxwidth;
    assert((scaletbl_index == 0) || (scaletbl_index == 1));
    *dst_ptr++ = (uint8_t)(SumPixels(boxwidth, src_ptr + ix) *
                               scaletbl[scaletbl_index] >>
                           16);
  }
}

static void ScaleAddCols2_16_C(int dst_width,
                               int boxheight,
                               int x,
                               int dx,
                               const uint32_t* src_ptr,
                               uint16_t* dst_ptr) {
  int i;
  int scaletbl[2];
  int minboxwidth = dx >> 16;
  int boxwidth;
  scaletbl[0] = 65536 / (MIN1(minboxwidth) * boxheight);
  scaletbl[1] = 65536 / (MIN1(minboxwidth + 1) * boxheight);
  for (i = 0; i < dst_width; ++i) {
    int ix = x >> 16;
    x += dx;
    boxwidth = MIN1((x >> 16) - ix);
    int scaletbl_index = boxwidth - minboxwidth;
    assert((scaletbl_index == 0) || (scaletbl_index == 1));
    *dst_ptr++ =
        SumPixels_16(boxwidth, src_ptr + ix) * scaletbl[scaletbl_index] >> 16;
  }
}

static void ScaleAddCols0_C(int dst_width,
                            int boxheight,
                            int x,
                            int dx,
                            const uint16_t* src_ptr,
                            uint8_t* dst_ptr) {
  int scaleval = 65536 / boxheight;
  int i;
  (void)dx;
  src_ptr += (x >> 16);
  for (i = 0; i < dst_width; ++i) {
    *dst_ptr++ = (uint8_t)(src_ptr[i] * scaleval >> 16);
  }
}

static void ScaleAddCols1_C(int dst_width,
                            int boxheight,
                            int x,
                            int dx,
                            const uint16_t* src_ptr,
                            uint8_t* dst_ptr) {
  int boxwidth = MIN1(dx >> 16);
  int scaleval = 65536 / (boxwidth * boxheight);
  int i;
  x >>= 16;
  for (i = 0; i < dst_width; ++i) {
    *dst_ptr++ = (uint8_t)(SumPixels(boxwidth, src_ptr + x) * scaleval >> 16);
    x += boxwidth;
  }
}

static void ScaleAddCols1_16_C(int dst_width,
                               int boxheight,
                               int x,
                               int dx,
                               const uint32_t* src_ptr,
                               uint16_t* dst_ptr) {
  int boxwidth = MIN1(dx >> 16);
  int scaleval = 65536 / (boxwidth * boxheight);
  int i;
  for (i = 0; i < dst_width; ++i) {
    *dst_ptr++ = SumPixels_16(boxwidth, src_ptr + x) * scaleval >> 16;
    x += boxwidth;
  }
}

// Scale plane down to any dimensions, with interpolation.
// (boxfilter).
//
// Same method as SimpleScale, which is fixed point, outputting
// one pixel of destination using fixed point (16.16) to step
// through source, sampling a box of pixel with simple
// averaging.
static int ScalePlaneBox(int src_width,
                         int src_height,
                         int dst_width,
                         int dst_height,
                         int src_stride,
                         int dst_stride,
                         const uint8_t* src_ptr,
                         uint8_t* dst_ptr) {
  int j, k;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  const int max_y = (src_height << 16);
  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterBox, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);
  {
    // Allocate a row buffer of uint16_t.
    align_buffer_64(row16, src_width * 2);
    if (!row16)
      return 1;
    void (*ScaleAddCols)(int dst_width, int boxheight, int x, int dx,
                         const uint16_t* src_ptr, uint8_t* dst_ptr) =
        (dx & 0xffff) ? ScaleAddCols2_C
                      : ((dx != 0x10000) ? ScaleAddCols1_C : ScaleAddCols0_C);
    void (*ScaleAddRow)(const uint8_t* src_ptr, uint16_t* dst_ptr,
                        int src_width) = ScaleAddRow_C;

    for (j = 0; j < dst_height; ++j) {
      int boxheight;
      int iy = y >> 16;
      const uint8_t* src = src_ptr + iy * (int64_t)src_stride;
      y += dy;
      if (y > max_y) {
        y = max_y;
      }
      boxheight = MIN1((y >> 16) - iy);
      memset(row16, 0, src_width * 2);
      for (k = 0; k < boxheight; ++k) {
        ScaleAddRow(src, (uint16_t*)(row16), src_width);
        src += src_stride;
      }
      ScaleAddCols(dst_width, boxheight, x, dx, (uint16_t*)(row16), dst_ptr);
      dst_ptr += dst_stride;
    }
    free_aligned_buffer_64(row16);
  }
  return 0;
}

static int ScalePlaneBox_16(int src_width,
                            int src_height,
                            int dst_width,
                            int dst_height,
                            int src_stride,
                            int dst_stride,
                            const uint16_t* src_ptr,
                            uint16_t* dst_ptr) {
  int j, k;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  const int max_y = (src_height << 16);
  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterBox, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);
  {
    // Allocate a row buffer of uint32_t.
    align_buffer_64(row32, src_width * 4);
    if (!row32)
      return 1;
    void (*ScaleAddCols)(int dst_width, int boxheight, int x, int dx,
                         const uint32_t* src_ptr, uint16_t* dst_ptr) =
        (dx & 0xffff) ? ScaleAddCols2_16_C : ScaleAddCols1_16_C;
    void (*ScaleAddRow)(const uint16_t* src_ptr, uint32_t* dst_ptr,
                        int src_width) = ScaleAddRow_16_C;

#if defined(HAS_SCALEADDROW_16_SSE2)
    if (TestCpuFlag(kCpuHasSSE2) && IS_ALIGNED(src_width, 16)) {
      ScaleAddRow = ScaleAddRow_16_SSE2;
    }
#endif

    for (j = 0; j < dst_height; ++j) {
      int boxheight;
      int iy = y >> 16;
      const uint16_t* src = src_ptr + iy * (int64_t)src_stride;
      y += dy;
      if (y > max_y) {
        y = max_y;
      }
      boxheight = MIN1((y >> 16) - iy);
      memset(row32, 0, src_width * 4);
      for (k = 0; k < boxheight; ++k) {
        ScaleAddRow(src, (uint32_t*)(row32), src_width);
        src += src_stride;
      }
      ScaleAddCols(dst_width, boxheight, x, dx, (uint32_t*)(row32), dst_ptr);
      dst_ptr += dst_stride;
    }
    free_aligned_buffer_64(row32);
  }
  return 0;
}

// Scale plane down with bilinear interpolation.
static int ScalePlaneBilinearDown(int src_width,
                                  int src_height,
                                  int dst_width,
                                  int dst_height,
                                  int src_stride,
                                  int dst_stride,
                                  const uint8_t* src_ptr,
                                  uint8_t* dst_ptr,
                                  enum FilterMode filtering) {
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  // TODO(fbarchard): Consider not allocating row buffer for kFilterLinear.
  // Allocate a row buffer.
  align_buffer_64(row, src_width);
  if (!row)
    return 1;

  const int max_y = (src_height - 1) << 16;
  int j;
  void (*ScaleFilterCols)(uint8_t* dst_ptr, const uint8_t* src_ptr,
                          int dst_width, int x, int dx) =
      (src_width >= 32768) ? ScaleFilterCols64_C : ScaleFilterCols_C;
  void (*InterpolateRow)(uint8_t* dst_ptr, const uint8_t* src_ptr,
                         ptrdiff_t src_stride, int dst_width,
                         int source_y_fraction) = InterpolateRow_C;
  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (y > max_y) {
    y = max_y;
  }

  for (j = 0; j < dst_height; ++j) {
    int yi = y >> 16;
    const uint8_t* src = src_ptr + yi * (int64_t)src_stride;
    if (filtering == kFilterLinear) {
      ScaleFilterCols(dst_ptr, src, dst_width, x, dx);
    } else {
      int yf = (y >> 8) & 255;
      InterpolateRow(row, src, src_stride, src_width, yf);
      ScaleFilterCols(dst_ptr, row, dst_width, x, dx);
    }
    dst_ptr += dst_stride;
    y += dy;
    if (y > max_y) {
      y = max_y;
    }
  }
  free_aligned_buffer_64(row);
  return 0;
}

static int ScalePlaneBilinearDown_16(int src_width,
                                     int src_height,
                                     int dst_width,
                                     int dst_height,
                                     int src_stride,
                                     int dst_stride,
                                     const uint16_t* src_ptr,
                                     uint16_t* dst_ptr,
                                     enum FilterMode filtering) {
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  // TODO(fbarchard): Consider not allocating row buffer for kFilterLinear.
  // Allocate a row buffer.
  align_buffer_64(row, src_width * 2);
  if (!row)
    return 1;

  const int max_y = (src_height - 1) << 16;
  int j;
  void (*ScaleFilterCols)(uint16_t* dst_ptr, const uint16_t* src_ptr,
                          int dst_width, int x, int dx) =
      (src_width >= 32768) ? ScaleFilterCols64_16_C : ScaleFilterCols_16_C;
  void (*InterpolateRow)(uint16_t* dst_ptr, const uint16_t* src_ptr,
                         ptrdiff_t src_stride, int dst_width,
                         int source_y_fraction) = InterpolateRow_16_C;
  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (y > max_y) {
    y = max_y;
  }

  for (j = 0; j < dst_height; ++j) {
    int yi = y >> 16;
    const uint16_t* src = src_ptr + yi * (int64_t)src_stride;
    if (filtering == kFilterLinear) {
      ScaleFilterCols(dst_ptr, src, dst_width, x, dx);
    } else {
      int yf = (y >> 8) & 255;
      InterpolateRow((uint16_t*)row, src, src_stride, src_width, yf);
      ScaleFilterCols(dst_ptr, (uint16_t*)row, dst_width, x, dx);
    }
    dst_ptr += dst_stride;
    y += dy;
    if (y > max_y) {
      y = max_y;
    }
  }
  free_aligned_buffer_64(row);
  return 0;
}

// Scale up down with bilinear interpolation.
static int ScalePlaneBilinearUp(int src_width,
                                int src_height,
                                int dst_width,
                                int dst_height,
                                int src_stride,
                                int dst_stride,
                                const uint8_t* src_ptr,
                                uint8_t* dst_ptr,
                                enum FilterMode filtering) {
  int j;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  const int max_y = (src_height - 1) << 16;
  void (*InterpolateRow)(uint8_t* dst_ptr, const uint8_t* src_ptr,
                         ptrdiff_t src_stride, int dst_width,
                         int source_y_fraction) = InterpolateRow_C;
  void (*ScaleFilterCols)(uint8_t* dst_ptr, const uint8_t* src_ptr,
                          int dst_width, int x, int dx) =
      filtering ? ScaleFilterCols_C : ScaleCols_C;
  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (filtering && src_width >= 32768) {
    ScaleFilterCols = ScaleFilterCols64_C;
  }
  if (!filtering && src_width * 2 == dst_width && x < 0x8000) {
    ScaleFilterCols = ScaleColsUp2_C;
  }

  if (y > max_y) {
    y = max_y;
  }
  {
    int yi = y >> 16;
    const uint8_t* src = src_ptr + yi * (int64_t)src_stride;

    // Allocate 2 row buffers.
    const int row_size = (dst_width + 31) & ~31;
    align_buffer_64(row, row_size * 2);
    if (!row)
      return 1;

    uint8_t* rowptr = row;
    int rowstride = row_size;
    int lasty = yi;

    ScaleFilterCols(rowptr, src, dst_width, x, dx);
    if (src_height > 1) {
      src += src_stride;
    }
    ScaleFilterCols(rowptr + rowstride, src, dst_width, x, dx);
    if (src_height > 2) {
      src += src_stride;
    }

    for (j = 0; j < dst_height; ++j) {
      yi = y >> 16;
      if (yi != lasty) {
        if (y > max_y) {
          y = max_y;
          yi = y >> 16;
          src = src_ptr + yi * (int64_t)src_stride;
        }
        if (yi != lasty) {
          ScaleFilterCols(rowptr, src, dst_width, x, dx);
          rowptr += rowstride;
          rowstride = -rowstride;
          lasty = yi;
          if ((y + 65536) < max_y) {
            src += src_stride;
          }
        }
      }
      if (filtering == kFilterLinear) {
        InterpolateRow(dst_ptr, rowptr, 0, dst_width, 0);
      } else {
        int yf = (y >> 8) & 255;
        InterpolateRow(dst_ptr, rowptr, rowstride, dst_width, yf);
      }
      dst_ptr += dst_stride;
      y += dy;
    }
    free_aligned_buffer_64(row);
  }
  return 0;
}

// Scale plane, horizontally up by 2 times.
// Uses linear filter horizontally, nearest vertically.
// This is an optimized version for scaling up a plane to 2 times of
// its original width, using linear interpolation.
// This is used to scale U and V planes of I422 to I444.
static void ScalePlaneUp2_Linear(int src_width,
                                 int src_height,
                                 int dst_width,
                                 int dst_height,
                                 int src_stride,
                                 int dst_stride,
                                 const uint8_t* src_ptr,
                                 uint8_t* dst_ptr) {
  void (*ScaleRowUp)(const uint8_t* src_ptr, uint8_t* dst_ptr, int dst_width) =
      ScaleRowUp2_Linear_Any_C;
  int i;
  int y;
  int dy;

  (void)src_width;
  // This function can only scale up by 2 times horizontally.
  assert(src_width == ((dst_width + 1) / 2));

  if (dst_height == 1) {
    ScaleRowUp(src_ptr + ((src_height - 1) / 2) * (int64_t)src_stride, dst_ptr,
               dst_width);
  } else {
    dy = FixedDiv(src_height - 1, dst_height - 1);
    y = (1 << 15) - 1;
    for (i = 0; i < dst_height; ++i) {
      ScaleRowUp(src_ptr + (y >> 16) * (int64_t)src_stride, dst_ptr, dst_width);
      dst_ptr += dst_stride;
      y += dy;
    }
  }
}

// Scale plane, up by 2 times.
// This is an optimized version for scaling up a plane to 2 times of
// its original size, using bilinear interpolation.
// This is used to scale U and V planes of I420 to I444.
static void ScalePlaneUp2_Bilinear(int src_width,
                                   int src_height,
                                   int dst_width,
                                   int dst_height,
                                   int src_stride,
                                   int dst_stride,
                                   const uint8_t* src_ptr,
                                   uint8_t* dst_ptr) {
  void (*Scale2RowUp)(const uint8_t* src_ptr, ptrdiff_t src_stride,
                      uint8_t* dst_ptr, ptrdiff_t dst_stride, int dst_width) =
      ScaleRowUp2_Bilinear_Any_C;
  int x;

  (void)src_width;
  // This function can only scale up by 2 times.
  assert(src_width == ((dst_width + 1) / 2));
  assert(src_height == ((dst_height + 1) / 2));

  Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  dst_ptr += dst_stride;
  for (x = 0; x < src_height - 1; ++x) {
    Scale2RowUp(src_ptr, src_stride, dst_ptr, dst_stride, dst_width);
    src_ptr += src_stride;
    // TODO(fbarchard): Test performance of writing one row of destination at a
    // time.
    dst_ptr += 2 * dst_stride;
  }
  if (!(dst_height & 1)) {
    Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  }
}

// Scale at most 14 bit plane, horizontally up by 2 times.
// This is an optimized version for scaling up a plane to 2 times of
// its original width, using linear interpolation.
// stride is in count of uint16_t.
// This is used to scale U and V planes of I210 to I410 and I212 to I412.
static void ScalePlaneUp2_12_Linear(int src_width,
                                    int src_height,
                                    int dst_width,
                                    int dst_height,
                                    int src_stride,
                                    int dst_stride,
                                    const uint16_t* src_ptr,
                                    uint16_t* dst_ptr) {
  void (*ScaleRowUp)(const uint16_t* src_ptr, uint16_t* dst_ptr,
                     int dst_width) = ScaleRowUp2_Linear_16_Any_C;
  int i;
  int y;
  int dy;

  (void)src_width;
  // This function can only scale up by 2 times horizontally.
  assert(src_width == ((dst_width + 1) / 2));

  if (dst_height == 1) {
    ScaleRowUp(src_ptr + ((src_height - 1) / 2) * (int64_t)src_stride, dst_ptr,
               dst_width);
  } else {
    dy = FixedDiv(src_height - 1, dst_height - 1);
    y = (1 << 15) - 1;
    for (i = 0; i < dst_height; ++i) {
      ScaleRowUp(src_ptr + (y >> 16) * (int64_t)src_stride, dst_ptr, dst_width);
      dst_ptr += dst_stride;
      y += dy;
    }
  }
}

// Scale at most 12 bit plane, up by 2 times.
// This is an optimized version for scaling up a plane to 2 times of
// its original size, using bilinear interpolation.
// stride is in count of uint16_t.
// This is used to scale U and V planes of I010 to I410 and I012 to I412.
static void ScalePlaneUp2_12_Bilinear(int src_width,
                                      int src_height,
                                      int dst_width,
                                      int dst_height,
                                      int src_stride,
                                      int dst_stride,
                                      const uint16_t* src_ptr,
                                      uint16_t* dst_ptr) {
  void (*Scale2RowUp)(const uint16_t* src_ptr, ptrdiff_t src_stride,
                      uint16_t* dst_ptr, ptrdiff_t dst_stride, int dst_width) =
      ScaleRowUp2_Bilinear_16_Any_C;
  int x;

  (void)src_width;
  // This function can only scale up by 2 times.
  assert(src_width == ((dst_width + 1) / 2));
  assert(src_height == ((dst_height + 1) / 2));

  Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  dst_ptr += dst_stride;
  for (x = 0; x < src_height - 1; ++x) {
    Scale2RowUp(src_ptr, src_stride, dst_ptr, dst_stride, dst_width);
    src_ptr += src_stride;
    dst_ptr += 2 * dst_stride;
  }
  if (!(dst_height & 1)) {
    Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  }
}

static void ScalePlaneUp2_16_Linear(int src_width,
                                    int src_height,
                                    int dst_width,
                                    int dst_height,
                                    int src_stride,
                                    int dst_stride,
                                    const uint16_t* src_ptr,
                                    uint16_t* dst_ptr) {
  void (*ScaleRowUp)(const uint16_t* src_ptr, uint16_t* dst_ptr,
                     int dst_width) = ScaleRowUp2_Linear_16_Any_C;
  int i;
  int y;
  int dy;

  (void)src_width;
  // This function can only scale up by 2 times horizontally.
  assert(src_width == ((dst_width + 1) / 2));

  if (dst_height == 1) {
    ScaleRowUp(src_ptr + ((src_height - 1) / 2) * (int64_t)src_stride, dst_ptr,
               dst_width);
  } else {
    dy = FixedDiv(src_height - 1, dst_height - 1);
    y = (1 << 15) - 1;
    for (i = 0; i < dst_height; ++i) {
      ScaleRowUp(src_ptr + (y >> 16) * (int64_t)src_stride, dst_ptr, dst_width);
      dst_ptr += dst_stride;
      y += dy;
    }
  }
}

static void ScalePlaneUp2_16_Bilinear(int src_width,
                                      int src_height,
                                      int dst_width,
                                      int dst_height,
                                      int src_stride,
                                      int dst_stride,
                                      const uint16_t* src_ptr,
                                      uint16_t* dst_ptr) {
  void (*Scale2RowUp)(const uint16_t* src_ptr, ptrdiff_t src_stride,
                      uint16_t* dst_ptr, ptrdiff_t dst_stride, int dst_width) =
      ScaleRowUp2_Bilinear_16_Any_C;
  int x;

  (void)src_width;
  // This function can only scale up by 2 times.
  assert(src_width == ((dst_width + 1) / 2));
  assert(src_height == ((dst_height + 1) / 2));

  Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  dst_ptr += dst_stride;
  for (x = 0; x < src_height - 1; ++x) {
    Scale2RowUp(src_ptr, src_stride, dst_ptr, dst_stride, dst_width);
    src_ptr += src_stride;
    dst_ptr += 2 * dst_stride;
  }
  if (!(dst_height & 1)) {
    Scale2RowUp(src_ptr, 0, dst_ptr, 0, dst_width);
  }
}

static int ScalePlaneBilinearUp_16(int src_width,
                                   int src_height,
                                   int dst_width,
                                   int dst_height,
                                   int src_stride,
                                   int dst_stride,
                                   const uint16_t* src_ptr,
                                   uint16_t* dst_ptr,
                                   enum FilterMode filtering) {
  int j;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  const int max_y = (src_height - 1) << 16;
  void (*InterpolateRow)(uint16_t* dst_ptr, const uint16_t* src_ptr,
                         ptrdiff_t src_stride, int dst_width,
                         int source_y_fraction) = InterpolateRow_16_C;
  void (*ScaleFilterCols)(uint16_t* dst_ptr, const uint16_t* src_ptr,
                          int dst_width, int x, int dx) =
      filtering ? ScaleFilterCols_16_C : ScaleCols_16_C;
  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (filtering && src_width >= 32768) {
    ScaleFilterCols = ScaleFilterCols64_16_C;
  }
  if (!filtering && src_width * 2 == dst_width && x < 0x8000) {
    ScaleFilterCols = ScaleColsUp2_16_C;
  }
  if (y > max_y) {
    y = max_y;
  }
  {
    int yi = y >> 16;
    const uint16_t* src = src_ptr + yi * (int64_t)src_stride;

    // Allocate 2 row buffers.
    const int row_size = (dst_width + 31) & ~31;
    align_buffer_64(row, row_size * 4);
    int rowstride = row_size;
    int lasty = yi;
    uint16_t* rowptr = (uint16_t*)row;
    if (!row)
      return 1;

    ScaleFilterCols(rowptr, src, dst_width, x, dx);
    if (src_height > 1) {
      src += src_stride;
    }
    ScaleFilterCols(rowptr + rowstride, src, dst_width, x, dx);
    if (src_height > 2) {
      src += src_stride;
    }

    for (j = 0; j < dst_height; ++j) {
      yi = y >> 16;
      if (yi != lasty) {
        if (y > max_y) {
          y = max_y;
          yi = y >> 16;
          src = src_ptr + yi * (int64_t)src_stride;
        }
        if (yi != lasty) {
          ScaleFilterCols(rowptr, src, dst_width, x, dx);
          rowptr += rowstride;
          rowstride = -rowstride;
          lasty = yi;
          if ((y + 65536) < max_y) {
            src += src_stride;
          }
        }
      }
      if (filtering == kFilterLinear) {
        InterpolateRow(dst_ptr, rowptr, 0, dst_width, 0);
      } else {
        int yf = (y >> 8) & 255;
        InterpolateRow(dst_ptr, rowptr, rowstride, dst_width, yf);
      }
      dst_ptr += dst_stride;
      y += dy;
    }
    free_aligned_buffer_64(row);
  }
  return 0;
}

// Scale Plane to/from any dimensions, without interpolation.
// Fixed point math is used for performance: The upper 16 bits
// of x and dx is the integer part of the source position and
// the lower 16 bits are the fixed decimal part.

static void ScalePlaneSimple(int src_width,
                             int src_height,
                             int dst_width,
                             int dst_height,
                             int src_stride,
                             int dst_stride,
                             const uint8_t* src_ptr,
                             uint8_t* dst_ptr) {
  int i;
  void (*ScaleCols)(uint8_t* dst_ptr, const uint8_t* src_ptr, int dst_width,
                    int x, int dx) = ScaleCols_C;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterNone, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (src_width * 2 == dst_width && x < 0x8000) {
    ScaleCols = ScaleColsUp2_C;
  }

  for (i = 0; i < dst_height; ++i) {
    ScaleCols(dst_ptr, src_ptr + (y >> 16) * (int64_t)src_stride, dst_width, x,
              dx);
    dst_ptr += dst_stride;
    y += dy;
  }
}

static void ScalePlaneSimple_16(int src_width,
                                int src_height,
                                int dst_width,
                                int dst_height,
                                int src_stride,
                                int dst_stride,
                                const uint16_t* src_ptr,
                                uint16_t* dst_ptr) {
  int i;
  void (*ScaleCols)(uint16_t* dst_ptr, const uint16_t* src_ptr, int dst_width,
                    int x, int dx) = ScaleCols_16_C;
  // Initial source x/y coordinate and step values as 16.16 fixed point.
  int x = 0;
  int y = 0;
  int dx = 0;
  int dy = 0;
  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterNone, &x, &y,
             &dx, &dy);
  src_width = Abs(src_width);

  if (src_width * 2 == dst_width && x < 0x8000) {
    ScaleCols = ScaleColsUp2_16_C;
  }

  for (i = 0; i < dst_height; ++i) {
    ScaleCols(dst_ptr, src_ptr + (y >> 16) * (int64_t)src_stride, dst_width, x,
              dx);
    dst_ptr += dst_stride;
    y += dy;
  }
}

// Scale a plane.
// This function dispatches to a specialized scaler based on scale factor.
int ScalePlane(const uint8_t* src,
               int src_stride,
               int src_width,
               int src_height,
               uint8_t* dst,
               int dst_stride,
               int dst_width,
               int dst_height,
               enum FilterMode filtering) {
  // Simplify filtering when possible.
  filtering = ScaleFilterReduce(src_width, src_height, dst_width, dst_height,
                                filtering);

  // Negative height means invert the image.
  if (src_height < 0) {
    src_height = -src_height;
    src = src + (src_height - 1) * (int64_t)src_stride;
    src_stride = -src_stride;
  }
  // Use specialized scales to improve performance for common resolutions.
  // For example, all the 1/2 scalings will use ScalePlaneDown2()
  if (dst_width == src_width && dst_height == src_height) {
    // Straight copy.
    CopyPlane(src, src_stride, dst, dst_stride, dst_width, dst_height);
    return 0;
  }
  if (dst_width == src_width && filtering != kFilterBox) {
    int dy = 0;
    int y = 0;
    // When scaling down, use the center 2 rows to filter.
    // When scaling up, last row of destination uses the last 2 source rows.
    if (dst_height <= src_height) {
      dy = FixedDiv(src_height, dst_height);
      y = CENTERSTART(dy, -32768);  // Subtract 0.5 (32768) to center filter.
    } else if (src_height > 1 && dst_height > 1) {
      dy = FixedDiv1(src_height, dst_height);
    }
    // Arbitrary scale vertically, but unscaled horizontally.
    ScalePlaneVertical(src_height, dst_width, dst_height, src_stride,
                       dst_stride, src, dst, 0, y, dy, /*bpp=*/1, filtering);
    return 0;
  }
  if (filtering == kFilterBox && dst_height * 2 < src_height) {
    return ScalePlaneBox(src_width, src_height, dst_width, dst_height,
                         src_stride, dst_stride, src, dst);
  }
  if ((dst_width + 1) / 2 == src_width && filtering == kFilterLinear) {
    ScalePlaneUp2_Linear(src_width, src_height, dst_width, dst_height,
                         src_stride, dst_stride, src, dst);
    return 0;
  }
  if ((dst_height + 1) / 2 == src_height && (dst_width + 1) / 2 == src_width &&
      (filtering == kFilterBilinear || filtering == kFilterBox)) {
    ScalePlaneUp2_Bilinear(src_width, src_height, dst_width, dst_height,
                           src_stride, dst_stride, src, dst);
    return 0;
  }
  if (filtering && dst_height > src_height) {
    return ScalePlaneBilinearUp(src_width, src_height, dst_width, dst_height,
                                src_stride, dst_stride, src, dst, filtering);
  }
  if (filtering) {
    return ScalePlaneBilinearDown(src_width, src_height, dst_width, dst_height,
                                  src_stride, dst_stride, src, dst, filtering);
  }
  ScalePlaneSimple(src_width, src_height, dst_width, dst_height, src_stride,
                   dst_stride, src, dst);
  return 0;
}

int ScalePlane_16(const uint16_t* src,
                  int src_stride,
                  int src_width,
                  int src_height,
                  uint16_t* dst,
                  int dst_stride,
                  int dst_width,
                  int dst_height,
                  enum FilterMode filtering) {
  // Simplify filtering when possible.
  filtering = ScaleFilterReduce(src_width, src_height, dst_width, dst_height,
                                filtering);

  // Negative height means invert the image.
  if (src_height < 0) {
    src_height = -src_height;
    src = src + (src_height - 1) * (int64_t)src_stride;
    src_stride = -src_stride;
  }
  // Use specialized scales to improve performance for common resolutions.
  // For example, all the 1/2 scalings will use ScalePlaneDown2()
  if (dst_width == src_width && dst_height == src_height) {
    // Straight copy.
    CopyPlane_16(src, src_stride, dst, dst_stride, dst_width, dst_height);
    return 0;
  }
  if (dst_width == src_width && filtering != kFilterBox) {
    int dy = 0;
    int y = 0;
    // When scaling down, use the center 2 rows to filter.
    // When scaling up, last row of destination uses the last 2 source rows.
    if (dst_height <= src_height) {
      dy = FixedDiv(src_height, dst_height);
      y = CENTERSTART(dy, -32768);  // Subtract 0.5 (32768) to center filter.
      // When scaling up, ensure the last row of destination uses the last
      // source. Avoid divide by zero for dst_height but will do no scaling
      // later.
    } else if (src_height > 1 && dst_height > 1) {
      dy = FixedDiv1(src_height, dst_height);
    }
    // Arbitrary scale vertically, but unscaled horizontally.
    ScalePlaneVertical_16(src_height, dst_width, dst_height, src_stride,
                          dst_stride, src, dst, 0, y, dy, /*bpp=*/1, filtering);
    return 0;
  }
  if (filtering == kFilterBox && dst_height * 2 < src_height) {
    return ScalePlaneBox_16(src_width, src_height, dst_width, dst_height,
                            src_stride, dst_stride, src, dst);
  }
  if ((dst_width + 1) / 2 == src_width && filtering == kFilterLinear) {
    ScalePlaneUp2_16_Linear(src_width, src_height, dst_width, dst_height,
                            src_stride, dst_stride, src, dst);
    return 0;
  }
  if ((dst_height + 1) / 2 == src_height && (dst_width + 1) / 2 == src_width &&
      (filtering == kFilterBilinear || filtering == kFilterBox)) {
    ScalePlaneUp2_16_Bilinear(src_width, src_height, dst_width, dst_height,
                              src_stride, dst_stride, src, dst);
    return 0;
  }
  if (filtering && dst_height > src_height) {
    return ScalePlaneBilinearUp_16(src_width, src_height, dst_width, dst_height,
                                   src_stride, dst_stride, src, dst, filtering);
  }
  if (filtering) {
    return ScalePlaneBilinearDown_16(src_width, src_height, dst_width,
                                     dst_height, src_stride, dst_stride, src,
                                     dst, filtering);
  }
  ScalePlaneSimple_16(src_width, src_height, dst_width, dst_height, src_stride,
                      dst_stride, src, dst);
  return 0;
}

int ScalePlane_12(const uint16_t* src,
                  int src_stride,
                  int src_width,
                  int src_height,
                  uint16_t* dst,
                  int dst_stride,
                  int dst_width,
                  int dst_height,
                  enum FilterMode filtering) {
  // Simplify filtering when possible.
  filtering = ScaleFilterReduce(src_width, src_height, dst_width, dst_height,
                                filtering);

  // Negative height means invert the image.
  if (src_height < 0) {
    src_height = -src_height;
    src = src + (src_height - 1) * (int64_t)src_stride;
    src_stride = -src_stride;
  }

  if ((dst_width + 1) / 2 == src_width && filtering == kFilterLinear) {
    ScalePlaneUp2_12_Linear(src_width, src_height, dst_width, dst_height,
                            src_stride, dst_stride, src, dst);
    return 0;
  }
  if ((dst_height + 1) / 2 == src_height && (dst_width + 1) / 2 == src_width &&
      (filtering == kFilterBilinear || filtering == kFilterBox)) {
    ScalePlaneUp2_12_Bilinear(src_width, src_height, dst_width, dst_height,
                              src_stride, dst_stride, src, dst);
    return 0;
  }

  return ScalePlane_16(src, src_stride, src_width, src_height, dst, dst_stride,
                       dst_width, dst_height, filtering);
}