C# getpixels() gets the correct value on xp and vista but is slightly off when used on windows 7

Question

I have a C# program that works correctly on xp and vista but it needs to be used on windows 7, I have not been able to come up with a solution, it appears that getpixels just doesn't work right on windows 7.

I am getting one of the RGB values because I am dealing with tiff grayscale images.

 System.Drawing.Bitmap image;// this is in a separate class

 image = new Bitmap(destination);// this is in the constructor 

 Color t = image.GetPixel(j, i); // this is in a separate function
 int s = t.R 

when I print s, for example, image(0,0), it is supposed to be 220, it will be 221

I am doing edge detection on an image and I have to go through the image pixel by pixel, I have run the exact same program on XP,Vista,windows7 and windows 7 got different values.

It wouldn't let me post images at all and only one link.

http://img96.imageshack.us/img96/1559/mandrilly.png

img696.imageshack.us/img696/2844/newmany.png

img185.imageshack.us/img185/6124/edmandrilly.png

The first image is the original image, the second is the correct image, also the one I get with XP and Vista, the final image is the image when running the same program in Windows 7. There is not much of a visible difference but it matters for what I am doing.

Thanks for the help, it seems that I am having a hard time explaining my problem.

Answer 1

Are you sure your program is really correct, according to the documentation? Bugs like this sometimes mean that you're accidentally relying on undefined behavior.

Answer 2

If you mean Bitmap.GetPixel, that method returns a Color structure. I assume when you say it's "slightly off" that the RGB values of the returned color are slightly different than the value you're expecting.

This is probably due to your Windows 7 PC/image having a different color depth than your XP or Vista machines, or it may be that Windows 7 does something slightly different under the hood with .Net colors. This really shouldn't matter, except I suspect that your code is looking for a specific color value. It would help if you posted additional details.

Answer 3

I just ended up using libtiff.net.

http://bitmiracle.com/libtiff/