Convert RGB to YUV420 planar format in java

This Method shows how you can convert RGB data to YUV420 planar data in Java.

colorconvertRGB_IYUV_I420 is a public static method/function which expects RGB data in aRGB[] which is an int (4 bytes/pixel) array, followed by width & height of input image. Returns yuv[] which is a byte array containing yuv data.

Android refers this format as COLOR_FormatYUV420Planar
FourCC name for it is : IYUV & I420


public static byte[] colorconvertRGB_IYUV_I420(int[] aRGB, int width, int height) {
        final int frameSize = width * height;
        final int chromasize = frameSize / 4;
       
        int yIndex = 0;
        int uIndex = frameSize;
        int vIndex = frameSize + chromasize;
        byte [] yuv = new byte[width*height*3/2];
       
        int a, R, G, B, Y, U, V;
        int index = 0;
        for (int j = 0; j < height; j++) {
            for (int i = 0; i < width; i++) {

                //a = (aRGB[index] & 0xff000000) >> 24; //not using it right now
                R = (aRGB[index] & 0xff0000) >> 16;
                G = (aRGB[index] & 0xff00) >> 8;
                B = (aRGB[index] & 0xff) >> 0;

                Y = ((66 * R + 129 * G +  25 * B + 128) >> 8) +  16;
                U = (( -38 * R -  74 * G + 112 * B + 128) >> 8) + 128;
                V = (( 112 * R -  94 * G -  18 * B + 128) >> 8) + 128;

                yuv[yIndex++] = (byte) ((Y < 0) ? 0 : ((Y > 255) ? 255 : Y));
               
                if (j % 2 == 0 && index % 2 == 0)
                {
                    yuv[uIndex++] = (byte)((U < 0) ? 0 : ((U > 255) ? 255 : U));
                    yuv[vIndex++] = (byte)((V < 0) ? 0 : ((V > 255) ? 255 : V));
                }

                index ++;
            }
        }       
        return yuv;
    }