java 实现 Bitmap 转 YUV 数据

gistfile1.txt

    /**
     * YUV420sp
     *
     * @param inputWidth
     * @param inputHeight
     * @param scaled
     * @return
     */
    public static byte[] getYUV420sp(int inputWidth, int inputHeight, Bitmap scaled) {
        Log.d(TAG, "getYUV420sp: start");
        int[] argb = new int[inputWidth * inputHeight];
        scaled.getPixels(argb, 0, inputWidth, 0, 0, inputWidth, inputHeight);
        scaled.recycle();
        byte[] yuv = new byte[inputWidth * inputHeight * 3 / 2];
        encodeYUV420SP(yuv, argb, inputWidth, inputHeight);
        return yuv;
    }

    public static byte[] getYUV420sp(int inputWidth, int inputHeight, byte[] scaled) {
        Log.d(TAG, "getYUV420sp: start");
        int[] argb = new int[inputWidth * inputHeight];
        scaled.getPixels(argb, 0, inputWidth, 0, 0, inputWidth, inputHeight);
        scaled.recycle();
        byte[] yuv = new byte[inputWidth * inputHeight * 3 / 2];
        encodeYUV420SP(yuv, argb, inputWidth, inputHeight);
        return yuv;
    }


    /**
     * RGB转YUV420sp
     *
     * @param yuv420sp inputWidth * inputHeight * 3 / 2
     * @param argb     inputWidth * inputHeight
     * @param width
     * @param height
     */
    private static void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {
        // 帧图片的像素大小
        final int frameSize = width * height;
        // ---YUV数据---
        int Y, U, V;
        // Y的index从0开始
        int yIndex = 0;
        // UV的index从frameSize开始
        int uvIndex = frameSize;

        // ---颜色数据---
        int a, R, G, B;
        int argbIndex = 0;

        // ---循环所有像素点，RGB转YUV---
        for (int j = 0; j < height; j++) {
            for (int i = 0; i < width; i++) {

                // a is not used obviously
                a = (argb[argbIndex] & 0xff000000) >> 24;
                R = (argb[argbIndex] & 0xff0000) >> 16;
                G = (argb[argbIndex] & 0xff00) >> 8;
                B = (argb[argbIndex] & 0xff);
                
                argbIndex++;

                // well known RGB to YUV algorithm, 经典的转化算法，但是会导致转化后的图片灰度增加
                // 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;
                
                // 优化后的算法
                Y = (306 * R + 601 * G + 117 * B) >> 10;
                U = ((-173 * R - 339 * G + 512 * B) >> 10) + 128;
                V = ((512 * R - 429 * G - 83 * B) >> 10) + 128;

                // 取最大值
                Y = Math.max(0, Math.min(Y, 255));
                U = Math.max(0, Math.min(U, 255));
                V = Math.max(0, Math.min(V, 255));

                // NV21 has a plane of Y and interleaved planes of VU each
                // sampled by a factor of 2
                // meaning for every 4 Y pixels there are 1 V and 1 U. Note the
                // sampling is every other
                // pixel AND every other scanline.
                // ---Y---
                yuv420sp[yIndex++] = (byte) Y;
                // ---UV---
                if ((j % 2 == 0) && (i % 2 == 0)) {
                    yuv420sp[uvIndex++] = (byte) V;
                    yuv420sp[uvIndex++] = (byte) U;
                }
            }
        }
    }