Texture manipulation

Hi,

I would like to do some pixel manipulation on a texture in runtime. The code is working but I have performance problem. This is the goal: I get a pixel color from Texture1 and an other pixel color from Texture2. I separating the R, G, B components of the colors and add them together (R to R, G to G, and so on). After this I write back the result color to Texture2. This procedure is repeated many many times. It is working but the performance is too poor. The question is: Is there a better (faster) solution to this task than Getpixel/Setpixel? Thanks!