Android : YUV420 to RGB565 conversion in Android

YUV420 to RGB565 conversion in Android

Moseycode is an augmented reality barcode system that combines live camera data and 3D graphics. Due to limitations in the way that live camera data is rendered by the Android framework, if you want to overlay 3D graphics onto live camera data your only option is to convert the camera data into an OpenGL texture.

The method below does just that in Java – and it’s not impossibly slow either; it’s been optimized quite a lot. At the fallback camera preview dimensions of 176x144 it takes approximately 90ms to perform the conversion on my G1.

/**
 * Converts semi-planar YUV420 as generated for camera preview into RGB565
 * format for use as an OpenGL ES texture. It assumes that both the input
 * and output data are contiguous and start at zero.
 * 
 * @param yuvs the array of YUV420 semi-planar data
 * @param rgbs an array into which the RGB565 data will be written
 * @param width the number of pixels horizontally
 * @param height the number of pixels vertically
 */

//we tackle the conversion two pixels at a time for greater speed
private void toRGB565(byte[] yuvs, int width, int height, byte[] rgbs) {
    //the end of the luminance data
    final int lumEnd = width * height;
    //points to the next luminance value pair
    int lumPtr = 0;
    //points to the next chromiance value pair
    int chrPtr = lumEnd;
    //points to the next byte output pair of RGB565 value
    int outPtr = 0;
    //the end of the current luminance scanline
    int lineEnd = width;

    while (true) {

        //skip back to the start of the chromiance values when necessary
        if (lumPtr == lineEnd) {
            if (lumPtr == lumEnd) break; //we've reached the end
            //division here is a bit expensive, but's only done once per scanline
            chrPtr = lumEnd + ((lumPtr  >> 1) / width) * width;
            lineEnd += width;
        }

        //read the luminance and chromiance values
        final int Y1 = yuvs[lumPtr++] & 0xff; 
        final int Y2 = yuvs[lumPtr++] & 0xff; 
        final int Cr = (yuvs[chrPtr++] & 0xff) - 128; 
        final int Cb = (yuvs[chrPtr++] & 0xff) - 128;
        int R, G, B;

        //generate first RGB components
        B = Y1 + ((454 * Cb) >> 8);
        if(B < 0) B = 0; else if(B > 255) B = 255; 
        G = Y1 - ((88 * Cb + 183 * Cr) >> 8); 
        if(G < 0) G = 0; else if(G > 255) G = 255; 
        R = Y1 + ((359 * Cr) >> 8); 
        if(R < 0) R = 0; else if(R > 255) R = 255; 
        //NOTE: this assume little-endian encoding
        rgbs[outPtr++]  = (byte) (((G & 0x3c) << 3) | (B >> 3));
        rgbs[outPtr++]  = (byte) ((R & 0xf8) | (G >> 5));

        //generate second RGB components
        B = Y2 + ((454 * Cb) >> 8);
        if(B < 0) B = 0; else if(B > 255) B = 255; 
        G = Y2 - ((88 * Cb + 183 * Cr) >> 8); 
        if(G < 0) G = 0; else if(G > 255) G = 255; 
        R = Y2 + ((359 * Cr) >> 8); 
        if(R < 0) R = 0; else if(R > 255) R = 255; 
        //NOTE: this assume little-endian encoding
        rgbs[outPtr++]  = (byte) (((G & 0x3c) << 3) | (B >> 3));
        rgbs[outPtr++]  = (byte) ((R & 0xf8) | (G >> 5));
    }
}

출처 : http://blog.tomgibara.com/post/132956174/yuv420-to-rgb565-conversion-in-android