YUV420_888转RGB 格式

        最近在看android camera源码，在DngCreator.java 文件中看到YUV420_888转换成RGB代码，摘抄下来方便使用。代码路径：Android/sdk/platforms/android-35/android.jar!/android/hardware/camera2/DngCreator.class

1. 将YUV420_888先转换成YUV的格式。

    /**
     * Generate a direct RGB {@link ByteBuffer} from a YUV420_888 {@link Image}.
     */
    private static ByteBuffer convertToRGB(Image yuvImage) {
        // TODO: Optimize this with renderscript intrinsic.
        int width = yuvImage.getWidth();
        int height = yuvImage.getHeight();
        ByteBuffer buf = ByteBuffer.allocateDirect(BYTES_PER_RGB_PIX * width * height);

        Image.Plane yPlane = yuvImage.getPlanes()[0];
        Image.Plane uPlane = yuvImage.getPlanes()[1];
        Image.Plane vPlane = yuvImage.getPlanes()[2];

        ByteBuffer yBuf = yPlane.getBuffer();
        ByteBuffer uBuf = uPlane.getBuffer();
        ByteBuffer vBuf = vPlane.getBuffer();

        yBuf.rewind();
        uBuf.rewind();
        vBuf.rewind();

        int yRowStride = yPlane.getRowStride();
        int vRowStride = vPlane.getRowStride();
        int uRowStride = uPlane.getRowStride();

        int yPixStride = yPlane.getPixelStride();
        int vPixStride = vPlane.getPixelStride();
        int uPixStride = uPlane.getPixelStride();

        byte[] yuvPixel = { 0, 0, 0 };
        byte[] yFullRow = new byte[yPixStride * (width - 1) + 1];
        byte[] uFullRow = new byte[uPixStride * (width / 2 - 1) + 1];
        byte[] vFullRow = new byte[vPixStride * (width / 2 - 1) + 1];
        byte[] finalRow = new byte[BYTES_PER_RGB_PIX * width];
        for (int i = 0; i < height; i++) {
            int halfH = i / 2;
            yBuf.position(yRowStride * i);
            yBuf.get(yFullRow);
            uBuf.position(uRowStride * halfH);
            uBuf.get(uFullRow);
            vBuf.position(vRowStride * halfH);
            vBuf.get(vFullRow);
            for (int j = 0; j < width; j++) {
                int halfW = j / 2;
                yuvPixel[0] = yFullRow[yPixStride * j];
                yuvPixel[1] = uFullRow[uPixStride * halfW];
                yuvPixel[2] = vFullRow[vPixStride * halfW];
                yuvToRgb(yuvPixel, j * BYTES_PER_RGB_PIX, /*out*/finalRow);
            }
            buf.put(finalRow);
        }

        yBuf.rewind();
        uBuf.rewind();
        vBuf.rewind();
        buf.rewind();
        return buf;
    }

2.将YUV 转换成为RGB。

    /**
     * Convert a single YUV pixel to RGB.
     */
    private static void yuvToRgb(byte[] yuvData, int outOffset, /*out*/byte[] rgbOut) {
        final int COLOR_MAX = 255;

        float y = yuvData[0] & 0xFF;  // Y channel
        float cb = yuvData[1] & 0xFF; // U channel
        float cr = yuvData[2] & 0xFF; // V channel

        // convert YUV -> RGB (from JFIF's "Conversion to and from RGB" section)
        float r = y + 1.402f * (cr - 128);
        float g = y - 0.34414f * (cb - 128) - 0.71414f * (cr - 128);
        float b = y + 1.772f * (cb - 128);

        // clamp to [0,255]
        rgbOut[outOffset] = (byte) Math.max(0, Math.min(COLOR_MAX, r));
        rgbOut[outOffset + 1] = (byte) Math.max(0, Math.min(COLOR_MAX, g));
        rgbOut[outOffset + 2] = (byte) Math.max(0, Math.min(COLOR_MAX, b));
    }