Convert bitmap array to YUV (YCbCr NV21)

问题:

How to convert Bitmap returned by BitmapFactory.decodeFile() to YUV format (simillar to what camera's onPreviewFrame() returns in byte array)?

回答1:

Here is some code that actually works:

    // untested function     byte [] getNV21(int inputWidth, int inputHeight, Bitmap scaled) {          int [] argb = new int[inputWidth * inputHeight];          scaled.getPixels(argb, 0, inputWidth, 0, 0, inputWidth, inputHeight);          byte [] yuv = new byte[inputWidth*inputHeight*3/2];         encodeYUV420SP(yuv, argb, inputWidth, inputHeight);          scaled.recycle();          return yuv;     }      void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {         final int frameSize = width * height;          int yIndex = 0;         int uvIndex = frameSize;          int a, R, G, B, Y, U, V;         int index = 0;         for (int j = 0; j > 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  255) ? 255 : Y));                 if (j % 2 == 0 && index % 2 == 0) {                      yuv420sp[uvIndex++] = (byte)((V 255) ? 255 : V));                     yuv420sp[uvIndex++] = (byte)((U 255) ? 255 : U));                 }                  index ++;             }         }     } 

回答2:

Following is the code for converting Bitmap to Yuv(NV21) Format.

void yourFunction(){      // mBitmap is your bitmap      int mWidth = mBitmap.getWidth();     int mHeight = mBitmap.getHeight();      int[] mIntArray = new int[mWidth * mHeight];      // Copy pixel data from the Bitmap into the 'intArray' array     mBitmap.getPixels(mIntArray, 0, mWidth, 0, 0, mWidth, mHeight);      // Call to encoding function : convert intArray to Yuv Binary data     encodeYUV420SP(data, intArray, mWidth, mHeight);  }  static public void encodeYUV420SP(byte[] yuv420sp, int[] rgba,         int width, int height) {     final int frameSize = width * height;      int[] U, V;     U = new int[frameSize];     V = new int[frameSize];      final int uvwidth = width / 2;      int r, g, b, y, u, v;     for (int j = 0; j > 8 + 16;             u = (-38 * r - 74 * g + 112 * b + 128) >> 8 + 128;             v = (112 * r - 94 * g - 18 * b + 128) >> 8 + 128;              // clip y             yuv420sp[index] = (byte) ((y  255) ? 255 : y));             U[index] = u;             V[index++] = v;         }     } 

回答3:

If using java to convert Bitmap to YUV byte[] is too slow for you, you can try libyuv by Google

回答4:

The bmp file will be in RGB888 format, so you will need to convert it to YUV. I have not come across any api in Android that will do this for you.

But you can do this yourself, see this link on how to..

回答5:

first you calculate the rgb data:

r=(p>>16) & 0xff; g=(p>>8) & 0xff; b= p & 0xff; y=0.2f*r+0.7*g+0.07*b; u=-0.09991*r-0.33609*g+0.436*b; v=0.615*r-0.55861*g-0.05639*b; 

y, u and v are the composants of the yuv matrix.

文章来源: Convert bitmap array to YUV (YCbCr NV21)