Saving Grayscale image as real grayscale -- dotnet drawing api

bert
5/27/2005 12:00:00 AM

I want to save an image which I converted to grayscale as a real
grayscale image.

When I save the image and open it in photoshop, the mode is RGB
color/ 8bit.
I want the mode to be grayscale.

I've been searching for a solution for my problem for some time now
but I can't seem to find an answer.

Hopefully somebody can help me.
I know there are some .NET components around that I can use, but I
prefer to do it myself.

bert
5/27/2005 12:00:00 AM

Hi morten,

I know there is no grayscale pixelformat. The bitmap is a 8bpp format
wich is converted to grayscale using colormatrix.
I'm trying to find a way to save this RGB bitmap as grayscale.

The 16bppGrayscale pixalformat is indeed broken. It shouldn't be in
the framework sourcecode but somebody left it in :-(

On Fri, 27 May 2005 12:23:11 +0200, "Morten Wennevik"
[quoted text, click to view]

Morten Wennevik
5/27/2005 12:00:00 AM

Ah, now I get you.

If you have an 8bpp color bitmap to begin with. Simply convert the palette to grayscale.

ColorPalette pal = myBitmap.Palette;
for(int i = 0; i < pal.Entries.Length; i++)
{
Color c = pal.Entries[i];
int gray = (int)(c.R * 0.3086f + c.G * 0.6094f + c.B * 0.082f);
pal.Entries[i] = Color.FromArgb(255, gray, gray, gray);
}
myBitmap.Palette = pal;

[quoted text, click to view]

--
Happy coding!

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dotnet drawing api : Saving Grayscale image as real grayscale