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Android允许用户实时捕获摄像头的视频流,这在利用摄像头的AR应用中非常有用。可以利用摄像流实时做画面图像的分析,并做出许多有用的应用。比如人脸识别,条码识别,特定图像替换等等,不过大多数图像处理软件在处理时是需要RGB格式的图像,而默认的视频流是压缩的YUV格式,Android下是YUV420SP,这个格式,虽然可以在程序中修改,但是修改后好像不起作用,也就是说只能得到编码为YUV420SP的视频流,这就需要把YUV420SP的视频流转换成RGB格式的图像,用于图像识别。

Java代码

static public void decodeYUV420SP(byte[] rgbBuf, byte[] yuv420sp, int width, int height) {

final int frameSize = width * height;

if (rgbBuf == null)

throw new NullPointerException(”buffer ‘rgbBuf’ is null”);

if (rgbBuf.length < frameSize * 3)

throw new IllegalArgumentException(”buffer ‘rgbBuf’ size “

+ rgbBuf.length + ” < minimum ” + frameSize * 3);

if (yuv420sp == null)

throw new NullPointerException(”buffer ‘yuv420sp’ is null”);

if (yuv420sp.length < frameSize * 3 / 2)

throw new IllegalArgumentException(”buffer ‘yuv420sp’ size ” + yuv420sp.length

+ ” < minimum ” + frameSize * 3 / 2);

int i = 0, y = 0;

int uvp = 0, u = 0, v = 0;

int y1192 = 0, r = 0, g = 0, b = 0;

for (int j = 0, yp = 0; j < height; j++) {

uvp = frameSize + (j >> 1) * width;

u = 0;

v = 0;

for (i = 0; i < width; i++, yp++) {

y = (0xff & ((int) yuv420sp[yp])) - 16;

if (y < 0) y = 0;

if ((i & 1) == 0) {

v = (0xff & yuv420sp[uvp++]) - 128;

u = (0xff & yuv420sp[uvp++]) - 128;

}

y1192 = 1192 * y;

r = (y1192 + 1634 * v);

g = (y1192 - 833 * v - 400 * u);

b = (y1192 + 2066 * u);

if (r < 0) r = 0; else if (r > 262143) r = 262143;

if (g < 0) g = 0; else if (g > 262143) g = 262143;

if (b < 0) b = 0; else if (b > 262143) b = 262143;

rgbBuf[yp * 3] = (byte)(r >> 10);

rgbBuf[yp * 3 + 1] = (byte)(g >> 10);

rgbBuf[yp * 3 + 2] = (byte)(b >> 10);

}

}

}


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