Performance of C# Graphics

Question

Hi ~

I need to make some image processing feature in my application, i use the classes in the namespaces of System.Drawing. The function i need to implemenet is the image filter, that is need to create a matrix to convoloving every pixel of the image. When i use the classes in the System.Drawing e.g. Bitmap.SetPixel or Bitmap.GetPixel, i found that the performance is not good. Such as i convoloving the 640*480 image, it take about 1.5 mins to complete. I see the commerical software like photoshop can process much faster. Is it the classes in System.Drawing have not well performance, or it is better to use another graphics toolkit from third party ?

Thank :)