Comparing Bitmap Pixels to Colors

[Typpo]

Hi all,

I'm trying to compare a color returned by a Bitmap's GetPixel method to
a normal static color of the Color class. My problem: after setting a
pixel to a certain color, the color returned by GetPixel isn't
considered the same color anymore. Example code:

bmp.SetPixel(0, 0, Color.Blue);
Color cc = bmp.GetPixel(0, 0);

if (cc.Equals(Colo r.Blue))
{
MessageBox.Show ("Pixel is blue");
}
else
{
MessageBox.Show ("Pixel isn't blue");
}

....this program will always tell me that the pixel isn't blue. Is there
anything I'm doing wrong? What's the proper way to compare these colors?

Thanks in advance.

[Bob Powell [MVP]]

The compare routine looks at other properties such as the KnownColor flag to
verify equality. The only way to check is to see if the R, G, B and, if
needed, A values match.

--
Bob Powell [MVP]
Visual C#, System.Drawing

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"Typpo" <ot********@opt online.net> wrote in message
news:uu******** ******@TK2MSFTN GP09.phx.gbl...

Hi all,

I'm trying to compare a color returned by a Bitmap's GetPixel method to a
normal static color of the Color class. My problem: after setting a pixel
to a certain color, the color returned by GetPixel isn't considered the
same color anymore. Example code:

bmp.SetPixel(0, 0, Color.Blue);
Color cc = bmp.GetPixel(0, 0);

if (cc.Equals(Colo r.Blue))
{
MessageBox.Show ("Pixel is blue");
}
else
{
MessageBox.Show ("Pixel isn't blue");
}

...this program will always tell me that the pixel isn't blue. Is there
anything I'm doing wrong? What's the proper way to compare these colors?

Thanks in advance.

[Typpo]

Bob Powell [MVP] wrote:

The compare routine looks at other properties such as the KnownColor flag to
verify equality. The only way to check is to see if the R, G, B and, if
needed, A values match.

Thanks. The following method works for me.

private bool IsSameColor(Col or first, Color second)
{
if (first.A.Equals (second.A)
&& first.R.Equals( second.R)
&& first.G.Equals( second.G)
&& first.B.Equals( second.B))
return true;
else
return false;
}

[Morten Wennevik]

For speed optimization I would check Alpha last as most likely it is the
same in all pixels :)
--
Happy Coding!
Morten Wennevik [C# MVP]