conversion.cc

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/* SPDX-FileCopyrightText: 2001-2002 NaN Holding BV. All rights reserved.
 * SPDX-FileCopyrightText: 2024 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

 
#include "BLI_array.hh"
#include "BLI_rect.h"
#include "BLI_task.hh"
 
#include "IMB_filter.hh"
#include "IMB_imbuf.hh"
#include "IMB_imbuf_types.hh"
 
#include "IMB_colormanagement.hh"
#include "IMB_colormanagement_intern.hh"
 
#include "MEM_guardedalloc.h"
 
#include "OCIO_colorspace.hh"
 
/* -------------------------------------------------------------------- */

 
MINLINE void ushort_to_byte_v4(uchar b[4], const ushort us[4])
{
  b[0] = unit_ushort_to_uchar(us[0]);
  b[1] = unit_ushort_to_uchar(us[1]);
  b[2] = unit_ushort_to_uchar(us[2]);
  b[3] = unit_ushort_to_uchar(us[3]);
}
 
MINLINE uchar ftochar(float value)
{
  return unit_float_to_uchar_clamp(value);
}
 
MINLINE void ushort_to_byte_dither_v4(uchar b[4], const ushort us[4], float dither, int x, int y)
{
#define USHORTTOFLOAT(val) (float(val) / 65535.0f)
  float dither_value = dither_random_value(x, y) * 0.0033f * dither;
 
  b[0] = ftochar(dither_value + USHORTTOFLOAT(us[0]));
  b[1] = ftochar(dither_value + USHORTTOFLOAT(us[1]));
  b[2] = ftochar(dither_value + USHORTTOFLOAT(us[2]));
  b[3] = unit_ushort_to_uchar(us[3]);
 
#undef USHORTTOFLOAT
}
 
MINLINE void float_to_byte_dither_v4(uchar b[4], const float f[4], float dither, int x, int y)
{
  float dither_value = dither_random_value(x, y) * 0.0033f * dither;
 
  b[0] = ftochar(dither_value + f[0]);
  b[1] = ftochar(dither_value + f[1]);
  b[2] = ftochar(dither_value + f[2]);
  b[3] = unit_float_to_uchar_clamp(f[3]);
}
 
bool IMB_alpha_affects_rgb(const ImBuf *ibuf)
{
  return ibuf && (ibuf->flags & IB_alphamode_channel_packed) == 0;
}
 
void IMB_buffer_byte_from_float(uchar *rect_to,
                                const float *rect_from,
                                int channels_from,
                                float dither,
                                int profile_to,
                                int profile_from,
                                bool predivide,
                                int width,
                                int height,
                                int stride_to,
                                int stride_from,
                                int start_y)
{
  float tmp[4];
  int x, y;
 
  /* we need valid profiles */
  BLI_assert(profile_to != IB_PROFILE_NONE);
  BLI_assert(profile_from != IB_PROFILE_NONE);
 
  for (y = 0; y < height; y++) {
    if (channels_from == 1) {
      /* single channel input */
      const float *from = rect_from + size_t(stride_from) * y;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from++, to += 4) {
        to[0] = to[1] = to[2] = to[3] = unit_float_to_uchar_clamp(from[0]);
      }
    }
    else if (channels_from == 3) {
      /* RGB input */
      const float *from = rect_from + size_t(stride_from) * y * 3;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      if (profile_to == profile_from) {
        /* no color space conversion */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          rgb_float_to_uchar(to, from);
          to[3] = 255;
        }
      }
      else if (profile_to == IB_PROFILE_SRGB) {
        /* convert from linear to sRGB */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          linearrgb_to_srgb_v3_v3(tmp, from);
          rgb_float_to_uchar(to, tmp);
          to[3] = 255;
        }
      }
      else if (profile_to == IB_PROFILE_LINEAR_RGB) {
        /* convert from sRGB to linear */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          srgb_to_linearrgb_v3_v3(tmp, from);
          rgb_float_to_uchar(to, tmp);
          to[3] = 255;
        }
      }
    }
    else if (channels_from == 4) {
      /* RGBA input */
      const float *from = rect_from + size_t(stride_from) * y * 4;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      if (profile_to == profile_from) {
        /* no color space conversion */
        if (dither && predivide) {
          float straight[4];
          for (x = 0; x < width; x++, from += 4, to += 4) {
            premul_to_straight_v4_v4(straight, from);
            float_to_byte_dither_v4(to, straight, dither, x, y + start_y);
          }
        }
        else if (dither) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            float_to_byte_dither_v4(to, from, dither, x, y + start_y);
          }
        }
        else if (predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            premul_float_to_straight_uchar(to, from);
          }
        }
        else {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            rgba_float_to_uchar(to, from);
          }
        }
      }
      else if (profile_to == IB_PROFILE_SRGB) {
        /* convert from linear to sRGB */
        ushort us[4];
        float straight[4];
 
        if (dither && predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            premul_to_straight_v4_v4(straight, from);
            linearrgb_to_srgb_ushort4(us, from);
            ushort_to_byte_dither_v4(to, us, dither, x, y + start_y);
          }
        }
        else if (dither) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            linearrgb_to_srgb_ushort4(us, from);
            ushort_to_byte_dither_v4(to, us, dither, x, y + start_y);
          }
        }
        else if (predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            premul_to_straight_v4_v4(straight, from);
            linearrgb_to_srgb_ushort4(us, from);
            ushort_to_byte_v4(to, us);
          }
        }
        else {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            linearrgb_to_srgb_ushort4(us, from);
            ushort_to_byte_v4(to, us);
          }
        }
      }
      else if (profile_to == IB_PROFILE_LINEAR_RGB) {
        /* convert from sRGB to linear */
        if (dither && predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_predivide_v4(tmp, from);
            float_to_byte_dither_v4(to, tmp, dither, x, y + start_y);
          }
        }
        else if (dither) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_v4(tmp, from);
            float_to_byte_dither_v4(to, tmp, dither, x, y + start_y);
          }
        }
        else if (predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_predivide_v4(tmp, from);
            rgba_float_to_uchar(to, tmp);
          }
        }
        else {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_v4(tmp, from);
            rgba_float_to_uchar(to, tmp);
          }
        }
      }
    }
  }
}
 
void IMB_buffer_byte_from_float_mask(uchar *rect_to,
                                     const float *rect_from,
                                     int channels_from,
                                     float dither,
                                     bool predivide,
                                     int width,
                                     int height,
                                     int stride_to,
                                     int stride_from,
                                     char *mask)
{
  int x, y;
 
  for (y = 0; y < height; y++) {
    if (channels_from == 1) {
      /* single channel input */
      const float *from = rect_from + size_t(stride_from) * y;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from++, to += 4) {
        if (*mask++ == FILTER_MASK_USED) {
          to[0] = to[1] = to[2] = to[3] = unit_float_to_uchar_clamp(from[0]);
        }
      }
    }
    else if (channels_from == 3) {
      /* RGB input */
      const float *from = rect_from + size_t(stride_from) * y * 3;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from += 3, to += 4) {
        if (*mask++ == FILTER_MASK_USED) {
          rgb_float_to_uchar(to, from);
          to[3] = 255;
        }
      }
    }
    else if (channels_from == 4) {
      /* RGBA input */
      const float *from = rect_from + size_t(stride_from) * y * 4;
      uchar *to = rect_to + size_t(stride_to) * y * 4;
 
      if (dither && predivide) {
        float straight[4];
        for (x = 0; x < width; x++, from += 4, to += 4) {
          if (*mask++ == FILTER_MASK_USED) {
            premul_to_straight_v4_v4(straight, from);
            float_to_byte_dither_v4(to, straight, dither, x, y);
          }
        }
      }
      else if (dither) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          if (*mask++ == FILTER_MASK_USED) {
            float_to_byte_dither_v4(to, from, dither, x, y);
          }
        }
      }
      else if (predivide) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          if (*mask++ == FILTER_MASK_USED) {
            premul_float_to_straight_uchar(to, from);
          }
        }
      }
      else {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          if (*mask++ == FILTER_MASK_USED) {
            rgba_float_to_uchar(to, from);
          }
        }
      }
    }
  }
}
 
void IMB_buffer_float_from_byte(float *rect_to,
                                const uchar *rect_from,
                                int profile_to,
                                int profile_from,
                                bool predivide,
                                int width,
                                int height,
                                int stride_to,
                                int stride_from)
{
  float tmp[4];
  int x, y;
 
  /* we need valid profiles */
  BLI_assert(profile_to != IB_PROFILE_NONE);
  BLI_assert(profile_from != IB_PROFILE_NONE);
 
  /* RGBA input */
  for (y = 0; y < height; y++) {
    const uchar *from = rect_from + size_t(stride_from) * y * 4;
    float *to = rect_to + size_t(stride_to) * y * 4;
 
    if (profile_to == profile_from) {
      /* no color space conversion */
      for (x = 0; x < width; x++, from += 4, to += 4) {
        rgba_uchar_to_float(to, from);
      }
    }
    else if (profile_to == IB_PROFILE_LINEAR_RGB) {
      /* convert sRGB to linear */
      if (predivide) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          srgb_to_linearrgb_uchar4_predivide(to, from);
        }
      }
      else {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          srgb_to_linearrgb_uchar4(to, from);
        }
      }
    }
    else if (profile_to == IB_PROFILE_SRGB) {
      /* convert linear to sRGB */
      if (predivide) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          linearrgb_to_srgb_predivide_v4(to, tmp);
        }
      }
      else {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          linearrgb_to_srgb_v4(to, tmp);
        }
      }
    }
  }
}
 
void IMB_buffer_float_from_float(float *rect_to,
                                 const float *rect_from,
                                 int channels_from,
                                 int profile_to,
                                 int profile_from,
                                 bool predivide,
                                 int width,
                                 int height,
                                 int stride_to,
                                 int stride_from)
{
  int x, y;
 
  /* we need valid profiles */
  BLI_assert(profile_to != IB_PROFILE_NONE);
  BLI_assert(profile_from != IB_PROFILE_NONE);
 
  if (channels_from == 1) {
    /* single channel input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from++, to += 4) {
        to[0] = to[1] = to[2] = to[3] = from[0];
      }
    }
  }
  else if (channels_from == 3) {
    /* RGB input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y * 3;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      if (profile_to == profile_from) {
        /* no color space conversion */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          copy_v3_v3(to, from);
          to[3] = 1.0f;
        }
      }
      else if (profile_to == IB_PROFILE_LINEAR_RGB) {
        /* convert from sRGB to linear */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          srgb_to_linearrgb_v3_v3(to, from);
          to[3] = 1.0f;
        }
      }
      else if (profile_to == IB_PROFILE_SRGB) {
        /* convert from linear to sRGB */
        for (x = 0; x < width; x++, from += 3, to += 4) {
          linearrgb_to_srgb_v3_v3(to, from);
          to[3] = 1.0f;
        }
      }
    }
  }
  else if (channels_from == 4) {
    /* RGBA input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y * 4;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      if (profile_to == profile_from) {
        /* same profile, copy */
        memcpy(to, from, sizeof(float) * size_t(4) * width);
      }
      else if (profile_to == IB_PROFILE_LINEAR_RGB) {
        /* convert to sRGB to linear */
        if (predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_predivide_v4(to, from);
          }
        }
        else {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            srgb_to_linearrgb_v4(to, from);
          }
        }
      }
      else if (profile_to == IB_PROFILE_SRGB) {
        /* convert from linear to sRGB */
        if (predivide) {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            linearrgb_to_srgb_predivide_v4(to, from);
          }
        }
        else {
          for (x = 0; x < width; x++, from += 4, to += 4) {
            linearrgb_to_srgb_v4(to, from);
          }
        }
      }
    }
  }
}
 
void IMB_buffer_float_from_float_threaded(float *rect_to,
                                          const float *rect_from,
                                          int channels_from,
                                          int profile_to,
                                          int profile_from,
                                          bool predivide,
                                          int width,
                                          int height,
                                          int stride_to,
                                          int stride_from)
{
  using namespace blender;
  threading::parallel_for(IndexRange(height), 64, [&](const IndexRange y_range) {
    int64_t offset_from = y_range.first() * stride_from * channels_from;
    int64_t offset_to = y_range.first() * stride_to * 4;
    IMB_buffer_float_from_float(rect_to + offset_to,
                                rect_from + offset_from,
                                channels_from,
                                profile_to,
                                profile_from,
                                predivide,
                                width,
                                y_range.size(),
                                stride_to,
                                stride_from);
  });
}
 
void IMB_buffer_float_from_float_mask(float *rect_to,
                                      const float *rect_from,
                                      int channels_from,
                                      int width,
                                      int height,
                                      int stride_to,
                                      int stride_from,
                                      char *mask)
{
  int x, y;
 
  if (channels_from == 1) {
    /* single channel input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from++, to += 4) {
        if (*mask++ == FILTER_MASK_USED) {
          to[0] = to[1] = to[2] = to[3] = from[0];
        }
      }
    }
  }
  else if (channels_from == 3) {
    /* RGB input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y * 3;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from += 3, to += 4) {
        if (*mask++ == FILTER_MASK_USED) {
          copy_v3_v3(to, from);
          to[3] = 1.0f;
        }
      }
    }
  }
  else if (channels_from == 4) {
    /* RGBA input */
    for (y = 0; y < height; y++) {
      const float *from = rect_from + size_t(stride_from) * y * 4;
      float *to = rect_to + size_t(stride_to) * y * 4;
 
      for (x = 0; x < width; x++, from += 4, to += 4) {
        if (*mask++ == FILTER_MASK_USED) {
          copy_v4_v4(to, from);
        }
      }
    }
  }
}
 
void IMB_buffer_byte_from_byte(uchar *rect_to,
                               const uchar *rect_from,
                               int profile_to,
                               int profile_from,
                               bool predivide,
                               int width,
                               int height,
                               int stride_to,
                               int stride_from)
{
  float tmp[4];
  int x, y;
 
  /* we need valid profiles */
  BLI_assert(profile_to != IB_PROFILE_NONE);
  BLI_assert(profile_from != IB_PROFILE_NONE);
 
  /* always RGBA input */
  for (y = 0; y < height; y++) {
    const uchar *from = rect_from + size_t(stride_from) * y * 4;
    uchar *to = rect_to + size_t(stride_to) * y * 4;
 
    if (profile_to == profile_from) {
      /* same profile, copy */
      memcpy(to, from, sizeof(uchar[4]) * width);
    }
    else if (profile_to == IB_PROFILE_LINEAR_RGB) {
      /* convert to sRGB to linear */
      if (predivide) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          srgb_to_linearrgb_predivide_v4(tmp, tmp);
          rgba_float_to_uchar(to, tmp);
        }
      }
      else {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          srgb_to_linearrgb_v4(tmp, tmp);
          rgba_float_to_uchar(to, tmp);
        }
      }
    }
    else if (profile_to == IB_PROFILE_SRGB) {
      /* convert from linear to sRGB */
      if (predivide) {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          linearrgb_to_srgb_predivide_v4(tmp, tmp);
          rgba_float_to_uchar(to, tmp);
        }
      }
      else {
        for (x = 0; x < width; x++, from += 4, to += 4) {
          rgba_uchar_to_float(tmp, from);
          linearrgb_to_srgb_v4(tmp, tmp);
          rgba_float_to_uchar(to, tmp);
        }
      }
    }
  }
}

 
/* -------------------------------------------------------------------- */
 
void IMB_byte_from_float(ImBuf *ibuf)
{
  using namespace blender;
 
  /* Nothing to do if there's no float buffer */
  if (ibuf->float_buffer.data == nullptr) {
    return;
  }
 
  /* Allocate byte buffer if needed. */
  if (ibuf->byte_buffer.data == nullptr) {
    if (!IMB_alloc_byte_pixels(ibuf, false)) {
      return;
    }
  }
 
  const char *from_colorspace = (ibuf->float_buffer.colorspace == nullptr) ?
                                    IMB_colormanagement_role_colorspace_name_get(
                                        COLOR_ROLE_SCENE_LINEAR) :
                                    ibuf->float_buffer.colorspace->name().c_str();
  const char *to_colorspace = (ibuf->byte_buffer.colorspace == nullptr) ?
                                  IMB_colormanagement_role_colorspace_name_get(
                                      COLOR_ROLE_DEFAULT_BYTE) :
                                  ibuf->byte_buffer.colorspace->name().c_str();
  const bool predivide = IMB_alpha_affects_rgb(ibuf);
  ColormanageProcessor *processor = STREQ(from_colorspace, to_colorspace) ?
                                        nullptr :
                                        IMB_colormanagement_colorspace_processor_new(
                                            from_colorspace, to_colorspace);
  if (processor && IMB_colormanagement_processor_is_noop(processor)) {
    IMB_colormanagement_processor_free(processor);
    processor = nullptr;
  }
 
  /* At 4 floats per pixel, this is 32KB of data, and fits into typical CPU L1 cache. */
  static constexpr int grain_size = 2048;
  threading::parallel_for(
      IndexRange(IMB_get_pixel_count(ibuf)), grain_size, [&](const IndexRange range) {
        /* Copy chunk of source float pixels into a local buffer. */
        Array<float, grain_size * 4> buffer(range.size() * ibuf->channels);
        buffer.as_mutable_span().copy_from(
            Span(ibuf->float_buffer.data + range.first() * ibuf->channels, buffer.size()));
        /* Unpremultiply alpha if needed. */
        if (predivide) {
          IMB_unpremultiply_rect_float(buffer.data(), ibuf->channels, range.size(), 1);
        }
        /* Convert to byte color space if needed. */
        if (processor) {
          IMB_colormanagement_processor_apply(
              processor, buffer.data(), range.size(), 1, ibuf->channels, false);
        }
        /* Convert to bytes. */
        IMB_buffer_byte_from_float(ibuf->byte_buffer.data + range.first() * 4,
                                   buffer.data(),
                                   ibuf->channels,
                                   ibuf->dither,
                                   IB_PROFILE_SRGB,
                                   IB_PROFILE_SRGB,
                                   false,
                                   range.size(),
                                   1,
                                   ibuf->x,
                                   ibuf->x);
      });
  if (processor != nullptr) {
    IMB_colormanagement_processor_free(processor);
  }
 
  /* ensure user flag is reset */
  ibuf->userflags &= ~IB_RECT_INVALID;
}
 
void IMB_float_from_byte_ex(ImBuf *dst, const ImBuf *src, const rcti *region_to_update)
{
  using namespace blender;
 
  BLI_assert_msg(dst->float_buffer.data != nullptr,
                 "Destination buffer should have a float buffer assigned.");
  BLI_assert_msg(src->byte_buffer.data != nullptr,
                 "Source buffer should have a byte buffer assigned.");
  BLI_assert_msg(dst->x == src->x, "Source and destination buffer should have the same dimension");
  BLI_assert_msg(dst->y == src->y, "Source and destination buffer should have the same dimension");
  BLI_assert_msg(dst->channels = 4, "Destination buffer should have 4 channels.");
  BLI_assert_msg(region_to_update->xmin >= 0,
                 "Region to update should be clipped to the given buffers.");
  BLI_assert_msg(region_to_update->ymin >= 0,
                 "Region to update should be clipped to the given buffers.");
  BLI_assert_msg(region_to_update->xmax <= dst->x,
                 "Region to update should be clipped to the given buffers.");
  BLI_assert_msg(region_to_update->ymax <= dst->y,
                 "Region to update should be clipped to the given buffers.");
 
  const int region_width = BLI_rcti_size_x(region_to_update);
  const int region_height = BLI_rcti_size_y(region_to_update);
  const bool premultiply_alpha = IMB_alpha_affects_rgb(src);
 
  threading::parallel_for(
      IndexRange(region_to_update->ymin, region_height), 64, [&](const IndexRange y_range) {
        const uchar *src_ptr = src->byte_buffer.data;
        src_ptr += (region_to_update->xmin + y_range.first() * dst->x) * 4;
        float *dst_ptr = dst->float_buffer.data;
        dst_ptr += (region_to_update->xmin + y_range.first() * dst->x) * 4;
 
        /* Convert byte -> float without color or alpha conversions. */
        IMB_buffer_float_from_byte(dst_ptr,
                                   src_ptr,
                                   IB_PROFILE_SRGB,
                                   IB_PROFILE_SRGB,
                                   false,
                                   region_width,
                                   y_range.size(),
                                   src->x,
                                   dst->x);
 
        /* Convert to scene linear color space, and premultiply alpha if needed. */
        float *dst_ptr_line = dst_ptr;
        for ([[maybe_unused]] const int64_t y : y_range) {
          IMB_colormanagement_colorspace_to_scene_linear(
              dst_ptr_line, region_width, 1, dst->channels, src->byte_buffer.colorspace, false);
          if (premultiply_alpha) {
            IMB_premultiply_rect_float(dst_ptr_line, dst->channels, region_width, 1);
          }
          dst_ptr_line += 4 * dst->x;
        }
      });
}
 
void IMB_float_from_byte(ImBuf *ibuf)
{
  /* Nothing to do if there's no byte buffer. */
  if (ibuf->byte_buffer.data == nullptr) {
    return;
  }
 
  /* Allocate float buffer if needed. */
  if (ibuf->float_buffer.data == nullptr) {
    if (!IMB_alloc_float_pixels(ibuf, 4, false)) {
      return;
    }
  }
 
  rcti region_to_update;
  BLI_rcti_init(&region_to_update, 0, ibuf->x, 0, ibuf->y);
  IMB_float_from_byte_ex(ibuf, ibuf, &region_to_update);
}

 
/* -------------------------------------------------------------------- */
 
void IMB_color_to_bw(ImBuf *ibuf)
{
  float *rct_fl = ibuf->float_buffer.data;
  uchar *rct = ibuf->byte_buffer.data;
  size_t i;
 
  if (rct_fl) {
    if (ibuf->channels >= 3) {
      for (i = IMB_get_pixel_count(ibuf); i > 0; i--, rct_fl += ibuf->channels) {
        rct_fl[0] = rct_fl[1] = rct_fl[2] = IMB_colormanagement_get_luminance(rct_fl);
      }
    }
  }
 
  if (rct) {
    for (i = IMB_get_pixel_count(ibuf); i > 0; i--, rct += 4) {
      rct[0] = rct[1] = rct[2] = IMB_colormanagement_get_luminance_byte(rct);
    }
  }
}

 
/* -------------------------------------------------------------------- */
 
void IMB_saturation(ImBuf *ibuf, float sat)
{
  using namespace blender;
 
  const size_t pixel_count = IMB_get_pixel_count(ibuf);
  if (ibuf->byte_buffer.data != nullptr) {
    threading::parallel_for(IndexRange(pixel_count), 64 * 1024, [&](IndexRange range) {
      uchar *ptr = ibuf->byte_buffer.data + range.first() * 4;
      float rgb[3];
      float hsv[3];
      for ([[maybe_unused]] const int64_t i : range) {
        rgb_uchar_to_float(rgb, ptr);
        rgb_to_hsv_v(rgb, hsv);
        hsv_to_rgb(hsv[0], hsv[1] * sat, hsv[2], rgb + 0, rgb + 1, rgb + 2);
        rgb_float_to_uchar(ptr, rgb);
        ptr += 4;
      }
    });
  }
 
  if (ibuf->float_buffer.data != nullptr && ibuf->channels >= 3) {
    threading::parallel_for(IndexRange(pixel_count), 64 * 1024, [&](IndexRange range) {
      const int channels = ibuf->channels;
      float *ptr = ibuf->float_buffer.data + range.first() * channels;
      float hsv[3];
      for ([[maybe_unused]] const int64_t i : range) {
        rgb_to_hsv_v(ptr, hsv);
        hsv_to_rgb(hsv[0], hsv[1] * sat, hsv[2], ptr + 0, ptr + 1, ptr + 2);
        ptr += channels;
      }
    });
  }
}