package org.jcodec.scale;

import org.jcodec.common.model.Picture;
import org.jcodec.common.tools.MathUtil;

public class RgbToYuv420p implements Transform {
  public void transform(Picture img, Picture dst) {
    byte[] y = img.getData()[0];
    byte[][] dstData = dst.getData();
    byte[][] out = new byte[4][3];
    int offChr = 0, offLuma = 0, offSrc = 0, strideSrc = img.getWidth() * 3, strideDst = dst.getWidth();
    for (int i = 0; i < img.getHeight() >> 1; i++) {
      for (int j = 0; j < img.getWidth() >> 1; j++) {
        dstData[1][offChr] = 0;
        dstData[2][offChr] = 0;
        rgb2yuv(y[offSrc], y[offSrc + 1], y[offSrc + 2], out[0]);
        dstData[0][offLuma] = out[0][0];
        rgb2yuv(y[offSrc + strideSrc], y[offSrc + strideSrc + 1], y[offSrc + strideSrc + 2], out[1]);
        dstData[0][offLuma + strideDst] = out[1][0];
        offLuma++;
        rgb2yuv(y[offSrc + 3], y[offSrc + 4], y[offSrc + 5], out[2]);
        dstData[0][offLuma] = out[2][0];
        rgb2yuv(y[offSrc + strideSrc + 3], y[offSrc + strideSrc + 4], y[offSrc + strideSrc + 5], out[3]);
        dstData[0][offLuma + strideDst] = out[3][0];
        offLuma++;
        dstData[1][offChr] = (byte)(out[0][1] + out[1][1] + out[2][1] + out[3][1] + 2 >> 2);
        dstData[2][offChr] = (byte)(out[0][2] + out[1][2] + out[2][2] + out[3][2] + 2 >> 2);
        offChr++;
        offSrc += 6;
      } 
      offLuma += strideDst;
      offSrc += strideSrc;
    } 
  }
  
  public static final void rgb2yuv(byte r, byte g, byte b, byte[] out) {
    int rS = r + 128;
    int gS = g + 128;
    int bS = b + 128;
    int y = 66 * rS + 129 * gS + 25 * bS;
    int u = -38 * rS - 74 * gS + 112 * bS;
    int v = 112 * rS - 94 * gS - 18 * bS;
    y = y + 128 >> 8;
    u = u + 128 >> 8;
    v = v + 128 >> 8;
    out[0] = (byte)MathUtil.clip(y - 112, -128, 127);
    out[1] = (byte)MathUtil.clip(u, -128, 127);
    out[2] = (byte)MathUtil.clip(v, -128, 127);
  }
}