Extract black and white image from android camera's NV21 format

Question

I have done some google-ing around and couldn\'t find enough information about this format. It is the default format for camera preview. Can anyone suggest good sources of i

Answer 1

When you only need a grayscale camera preview, you could use a very simple renderscript:

# pragma version(1)
# pragma rs java_package_name(com.example.name)
# pragma rs_fp_relaxed

rs_allocation gIn;   // Allocation filled with camera preview data (byte[])
int previewwidth;    // camera preview width (int)

// the parallel executed kernel
void root(uchar4 *v_out, uint32_t x,uint32_t y){
   uchar c = rsGetElementAt_uchar(gIn,x+y*previewwidth); 
   *v_out = (uchar4){c,c,c,255};
}

Note : This is not faster than ScriptIntrinsicYuvToRGB (and a following ScriptIntrinsicColorMatrix to do the RGBA-> gray), but it runs with API 11+ (where the Intrinsics need Api 17+).