GetPixel/SetPixel very very slow...

I'm using C# and the latest release of Visual Studio 2005.

I have written a small filter to modify an image that is being loaded by some picture boxes. The filter works great except it takes about 30 to 40 seconds to run. How can I speed this up

public void GreyFilter()

{

Color pixel;

int t;

for (int y = 0; y < mainImage.Height; y++)

{

for (int x = 0; x < mainImage.Width; x++)

{

pixel = mainImage.GetPixel(x, y);

t = (pixel.R + pixel.G + pixel.B) / 3;

mainImage.SetPixel(x, y, Color.FromArgb(t, t, t));

}

}

MessageBox.Show("done");

}

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GetPixel/SetPixel very very slow...

shauli

I found an example for anyone that wants to do this:

http://msdn.microsoft.com/library/default.asp url=/library/en-us/dncscol/html/csharp11152001.asp
vindos
Are you familiar with C-style pointer arithmetic If so, I suggest you lock the image (see Bitmap.LockBits) and perform this per-pixel modification directly on the RGB data in memory, using "unsafe" code and pointers. That's very fast in my experience.

darrellp

Are you familiar with C-style pointer arithmetic If so, I suggest you lock the image (see Bitmap.LockBits) and perform this per-pixel modification directly on the RGB data in memory, using "unsafe" code and pointers. That's very fast in my experience.

Thank you. Do you have an example

Keehan
You may also want to consider using a ColorMatrix to modify the image as you draw it.

See Bob Powells site for more info:
http://www.bobpowell.net/grayscale.htm
Shinji

You may also want to consider using a ColorMatrix to modify the image as you draw it.

See Bob Powells site for more info:
http://www.bobpowell.net/grayscale.htm

Thank you. I'll give this a try.
GetPixel/SetPixel very very slow...

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