yuv2rgb.cc

/* Copyright 2015 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

// This is a collection of routines which converts various YUV image formats
// to ARGB.

#include "yuv2rgb.h"

#ifndef MAX
#define MAX(a, b) ({__typeof__(a) _a = (a); __typeof__(b) _b = (b); _a > _b ? _a : _b; })
#define MIN(a, b) ({__typeof__(a) _a = (a); __typeof__(b) _b = (b); _a < _b ? _a : _b; })
#endif

// This value is 2 ^ 18 - 1, and is used to clamp the RGB values before their ranges
// are normalized to eight bits.
static const int kMaxChannelValue = 262143;

static inline uint32 YUV2RGB(int nY, int nU, int nV) {
  nY -= 16;
  nU -= 128;
  nV -= 128;
  if (nY < 0) nY = 0;

  // This is the floating point equivalent. We do the conversion in integer
  // because some Android devices do not have floating point in hardware.
  // nR = (int)(1.164 * nY + 2.018 * nU);
  // nG = (int)(1.164 * nY - 0.813 * nV - 0.391 * nU);
  // nB = (int)(1.164 * nY + 1.596 * nV);

  int nR = (int)(1192 * nY + 1634 * nV);
  int nG = (int)(1192 * nY - 833 * nV - 400 * nU);
  int nB = (int)(1192 * nY + 2066 * nU);

  nR = MIN(kMaxChannelValue, MAX(0, nR));
  nG = MIN(kMaxChannelValue, MAX(0, nG));
  nB = MIN(kMaxChannelValue, MAX(0, nB));

  nR = (nR >> 10) & 0xff;
  nG = (nG >> 10) & 0xff;
  nB = (nB >> 10) & 0xff;

  return 0xff000000 | (nR << 16) | (nG << 8) | nB;
}

//  Accepts a YUV 4:2:0 image with a plane of 8 bit Y samples followed by
//  separate u and v planes with arbitrary row and column strides,
//  containing 8 bit 2x2 subsampled chroma samples.
//  Converts to a packed ARGB 32 bit output of the same pixel dimensions.
void ConvertYUV420ToARGB8888(const uint8* const yData, const uint8* const uData,
                             const uint8* const vData, uint32* const output,
                             const int width, const int height,
                             const int y_row_stride, const int uv_row_stride,
                             const int uv_pixel_stride) {
  uint32* out = output;

  for (int y = 0; y < height; y++) {
    const uint8* pY = yData + y_row_stride * y;

    const int uv_row_start = uv_row_stride * (y >> 1);
    const uint8* pU = uData + uv_row_start;
    const uint8* pV = vData + uv_row_start;

    for (int x = 0; x < width; x++) {
      const int uv_offset = (x >> 1) * uv_pixel_stride;
      *out++ = YUV2RGB(pY[x], pU[uv_offset], pV[uv_offset]);
    }
  }
}

//  Accepts a YUV 4:2:0 image with a plane of 8 bit Y samples followed by an
//  interleaved U/V plane containing 8 bit 2x2 subsampled chroma samples,
//  except the interleave order of U and V is reversed. Converts to a packed
//  ARGB 32 bit output of the same pixel dimensions.
void ConvertYUV420SPToARGB8888(const uint8* const yData,
                               const uint8* const uvData,
                               uint32* const output, const int width,
                               const int height) {
  const uint8* pY = yData;
  const uint8* pUV = uvData;
  uint32* out = output;

  for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
      int nY = *pY++;
      int offset = (y >> 1) * width + 2 * (x >> 1);
#ifdef __APPLE__
      int nU = pUV[offset];
      int nV = pUV[offset + 1];
#else
      int nV = pUV[offset];
      int nU = pUV[offset + 1];
#endif

      *out++ = YUV2RGB(nY, nU, nV);
    }
  }
}

// The same as above, but downsamples each dimension to half size.
void ConvertYUV420SPToARGB8888HalfSize(const uint8* const input,
                                       uint32* const output,
                                       int width, int height) {
  const uint8* pY = input;
  const uint8* pUV = input + (width * height);
  uint32* out = output;
  int stride = width;
  width >>= 1;
  height >>= 1;

  for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
      int nY = (pY[0] + pY[1] + pY[stride] + pY[stride + 1]) >> 2;
      pY += 2;
#ifdef __APPLE__
      int nU = *pUV++;
      int nV = *pUV++;
#else
      int nV = *pUV++;
      int nU = *pUV++;
#endif

      *out++ = YUV2RGB(nY, nU, nV);
    }
    pY += stride;
  }
}

//  Accepts a YUV 4:2:0 image with a plane of 8 bit Y samples followed by an
//  interleaved U/V plane containing 8 bit 2x2 subsampled chroma samples,
//  except the interleave order of U and V is reversed. Converts to a packed
//  RGB 565 bit output of the same pixel dimensions.
void ConvertYUV420SPToRGB565(const uint8* const input, uint16* const output,
                             const int width, const int height) {
  const uint8* pY = input;
  const uint8* pUV = input + (width * height);
  uint16 *out = output;

  for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
      int nY = *pY++;
      int offset = (y >> 1) * width + 2 * (x >> 1);
#ifdef __APPLE__
      int nU = pUV[offset];
      int nV = pUV[offset + 1];
#else
      int nV = pUV[offset];
      int nU = pUV[offset + 1];
#endif

      nY -= 16;
      nU -= 128;
      nV -= 128;
      if (nY < 0) nY = 0;

      // This is the floating point equivalent. We do the conversion in integer
      // because some Android devices do not have floating point in hardware.
      // nR = (int)(1.164 * nY + 2.018 * nU);
      // nG = (int)(1.164 * nY - 0.813 * nV - 0.391 * nU);
      // nB = (int)(1.164 * nY + 1.596 * nV);

      int nR = (int)(1192 * nY + 1634 * nV);
      int nG = (int)(1192 * nY - 833 * nV - 400 * nU);
      int nB = (int)(1192 * nY + 2066 * nU);

      nR = MIN(kMaxChannelValue, MAX(0, nR));
      nG = MIN(kMaxChannelValue, MAX(0, nG));
      nB = MIN(kMaxChannelValue, MAX(0, nB));

      // Shift more than for ARGB8888 and apply appropriate bitmask.
      nR = (nR >> 13) & 0x1f;
      nG = (nG >> 12) & 0x3f;
      nB = (nB >> 13) & 0x1f;

      // R is high 5 bits, G is middle 6 bits, and B is low 5 bits.
      *out++ = (nR << 11) | (nG << 5) | nB;
    }
  }
}