I have something like that:
[StructLayout(LayoutKind.Explicit)] public struct PixelColorRGBA { [FieldOffset(0)] public UInt32 ColorBGRA; [FieldOffset(0)] public byte Blue; [FieldOffset(1)] public byte Green; [FieldOffset(2)] public byte Red; [FieldOffset(3)] public byte Alpha; } What is the fastest way to copy PixelColorRGBA[w, h] to byte[w * h * 4] and vise versa?
I end up with the following code:
var source = new PixelColorRGBA[1000, 1000]; var destination = new byte[4000000]; { var start = DateTime.Now; unsafe { for (var q = 0; q < 100; q++) fixed (PixelColorRGBA* tmpSourcePtr = &source[0, 0]) { var sourcePtr = (IntPtr) tmpSourcePtr; Marshal.Copy(sourcePtr, destination, 0, 4000000); } } Console.WriteLine("MS: " + DateTime.Now.Subtract(start).TotalMilliseconds); } It takes 62 ms on my computer.
Try the following
PixelColorRGBA[,] source = ...; byte[] dest = source .Cast<PixelColorRGBA>() .SelectMany(x => new byte[] { x.Blue, x.Green, x.Red, x.Alpha }) .ToArray(); 
You can use
System.Buffer.BlockCopy(myArray, 0, byteArray, 0, length) or
System.Runtime.InteropServices.Marshal.Copy(myArray, 0, destPtr, length); 