how to decompose integer array to a byte array (pixel codings)

问题

Hi sorry for being annoying by rephrasing my question but I am just on the point of discovering my answer.

I have an array of int composed of RGB values, I need to decompose that int array into a byte array, but it should be in BGR order.

The array of int composed of RGB values is being created like so:

pix[index++] = (255 << 24) | (red << 16) | blue;

回答1:

C# code

        // convert integer array representing [argb] values to byte array representing [bgr] values
        private byte[] convertArray(int[] array)
        {
            byte[] newarray = new byte[array.Length * 3];

            for (int i = 0; i < array.Length; i++)
            {

                newarray[i * 3] = (byte)array[i];
                newarray[i * 3 + 1] = (byte)(array[i] >> 8);
                newarray[i * 3 + 2] = (byte)(array[i] >> 16);

            }
            return newarray;
        }

回答2:

#define N something
unsigned char bytes[N*3];
unsigned int  ints[N];

for(int i=0; i<N; i++) {
    bytes[i*3]   = ints[i];       // Blue
    bytes[i*3+1] = ints[i] >> 8;  // Green
    bytes[i*3+2] = ints[i] >> 16; // Red
}

回答3:

Using Linq:

        pix.SelectMany(i => new byte[] { 
            (byte)(i >> 0),
            (byte)(i >> 8),
            (byte)(i >> 16),
        }).ToArray();

Or

        return (from i in pix
                from x in new[] { 0, 8, 16 }
                select (byte)(i >> x)
               ).ToArray();

回答4:

Try to use Buffer Class

byte[] bytes = new byte[ints.Length*4];
Buffer.BlockCopy(ints, 0, bytes, 0, ints.Length * 4);

回答5:

r = (pix[index] >> 16) & 0xFF

the rest is similar, just change 16 to 8 or 24.

来源：https://stackoverflow.com/questions/392371/how-to-decompose-integer-array-to-a-byte-array-pixel-codings