将位图数组转换为 YUV（420 平面）？

Question

如何将使用 getDrawingCache() 创建的位图转换为 YUV420planar 格式？

位图是从这样的自定义视图创建的

view.setDrawingCacheEnabled(true);
bitmap = Bitmap.createScaledBitmap(board.getDrawingCache(), 320, 240, true);
board.setDrawingCacheEnabled(false);

这个问题很相似，但没有给出我正在寻找的相同格式。 Convert bitmap array to YUV (YCbCr NV21).

提前致谢。

Answer 1

对 YUV 格式的一些阅读帮助我弄清楚了。我只需要修改上面链接的代码的一小部分。对于任何有同样疑问的人

void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {
        final int frameSize = width * height;
    
        int yIndex = 0;
        int uIndex = frameSize;
        int vIndex = frameSize+((yuv420sp.length-frameSize)/2);
        System.out.println(yuv420sp.length+" "+frameSize);
        
    
        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; // a is not used obviously
                R = (argb[index] & 0xff0000) >> 16;
                G = (argb[index] & 0xff00) >> 8;
                B = (argb[index] & 0xff) >> 0;
    
                // well known RGB to YUV algorithm
                
                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; 
    
                // 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.
                yuv420sp[yIndex++] = (byte) ((Y < 0) ? 0 : ((Y > 255) ? 255 : Y));
                if (j % 2 == 0 && index % 2 == 0) { 
                    yuv420sp[uIndex++] = (byte)((U<0) ? 0 : ((U > 255) ? 255 : U));
                    yuv420sp[vIndex++] = (byte)((V<0) ? 0 : ((V > 255) ? 255 : V));
                }
    
                index ++;
            }
        }
    }