Hello Andrew, thank you for your reply. I already use the Lockbits-method and it gave a good performance boost once I implemented it weeks ago. But the performance is still not good enough. I decided to just use C# and no C, but maybe thats the only possibilty to make it faster now. One big problem is that a brightness change should work in realtime, the user should see the change immediately. I tried it with indexed bitmaps and a Change of the Palette of this bitmap, which works wonderful but is still a litle slow. For that reason I wanted to decrease the size of the bitmap before changing the brightness. For that reason I used the Bitmap-Constructor which requires a Bitmap and the Width and Height of the new Bitmap as paramters: public Bitmap ( System.Drawing.Image original , System.Int32 width , System.Int32 height) But the bitmap this constructor delivers doe not have a Palette. :sigh: So I cannot change the Brightness by changing the palette. :confused: Anyone has experience with that? :confused: :confused:

Hi Daniel, sorry, I've been on vacation for a while. No, my monitor/ graphics card won't display the whole Image, that's why i started to think about resizing it to a moderate size. Do you know, how I can do it in Direct Draw? I'm right now trying to figure out how fast it would be with Direct Draw (Managed DirectX 9.0).