opencv/android/android-jni/jni/yuv420sp2rgb.c

#include <string.h>
#include <jni.h>

#include <yuv420sp2rgb.h>

/*
 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.

 H V
 Y Sample Period      1 1
 U (Cb) Sample Period 2 2
 V (Cr) Sample Period 2 2
 */

/*
 size of a char:
 find . -name limits.h -exec grep CHAR_BIT {} \;
 */

#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

const int bytes_per_pixel = 2;
void color_convert_common(const unsigned char *pY, const unsigned char *pUV, int width, int height, unsigned char *buffer, int grey)
{

  int i, j;
  int nR, nG, nB;
  int nY, nU, nV;
  unsigned char *out = buffer;
  int offset = 0;

  if (grey)
  {
    memcpy(out,pY,width*height*sizeof(unsigned char));
  }
  else
    // YUV 4:2:0
    for (i = 0; i < height; i++)
    {
      for (j = 0; j < width; j++)
      {
        nY = *(pY + i * width + j);
        nV = *(pUV + (i / 2) * width + bytes_per_pixel * (j / 2));
        nU = *(pUV + (i / 2) * width + bytes_per_pixel * (j / 2) + 1);

        // Yuv Convert
        nY -= 16;
        nU -= 128;
        nV -= 128;

        if (nY < 0)
          nY = 0;

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

        nR = min(262143, max(0, nR));
        nG = min(262143, max(0, nG));
        nB = min(262143, max(0, nB));

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

        out[offset++] = (unsigned char)nR;
        out[offset++] = (unsigned char)nG;
        out[offset++] = (unsigned char)nB;
      }
    }

}