performance - Fast Converting RGBA to ARGB

Question

I am trying to convert a rgba buffer into argb, is there any way to improve the next algorithm, or any other faster way to perform such operation? Taking into account that the alpha value is not important once in the argb buffer, and should always end up as 0xFF.

int y, x, pixel;

for (y = 0; y < height; y++)
{
    for (x = 0; x < width; x++)
    {
     pixel = rgbaBuffer[y * width + x];
     argbBuffer[(height - y - 1) * width + x] = (pixel & 0xff00ff00) | ((pixel << 16) & 0x00ff0000) | ((pixel >> 16) & 0xff);
    }
}

Answer 1

I will focus only in the swap function:

typedef unsigned int Color32;

inline Color32 Color32Reverse(Color32 x)
{

    return
    // Source is in format: 0xAARRGGBB
        ((x & 0xFF000000) >> 24) | //______AA
        ((x & 0x00FF0000) >>  8) | //____RR__
        ((x & 0x0000FF00) <<  8) | //__GG____
        ((x & 0x000000FF) << 24);  //BB______
    // Return value is in format:  0xBBGGRRAA
}