C#-FORM: Problem using the function FromArgb(Int32)

[oberon]

Hi,
I am trying to use the function Color.FromArgb( Int32). The Int32 is on the format AARRGGBB, where AA is the alpha component.

My problem is that when I want to specify a solid color I need to give the alpha value FF, but that will not fit in an Int32 value (e.g. 0xFFFF0000 for solid red), since the largest Int32 value is 0x7FFFFFFF. How can I define a (near) solid color using this function?

[Plater]

It should?
.FromArgb() takes a 32 bit int.
32bits = 4 bytes
1 byte for AA
1 byte for RR
1 byte for GG
1 byte for BB

Although in your case I would use one of the overloads which is in this format:

Color.FromArgb(red,green,blue)

[oberon]

Thanks for your reply.

The overload Color.FromArgb( r, g, b) does not quite cover my needs as I want to be able to use alpha components also below 0xFF.

I found out that by placing the variable assignment inside an unchecked scope, it will compile:

unchecked
{
	Int32 argbValue = (Int32)0x9FFF0000;
	Color c = Color.FromArgb(argbValue);
}

If I don't include the "unchecked" it will not compile, complaining that the value "cannot be converted to a 'int' ".

[Plater]

You're killing me here guy.
LOOK at the function, shesh.

Here's another overload:
Color.FromArgb( alpha, red, green, blue);

If you have your heart set on using a single value, you can do it without having to use unchecked:

int argb=BitConverter.ToInt32(new byte[] { 0x9f, 0xff, 0x00, 0x00 }, 0); 
Color c = Color.FromArgb(argb);

[vladb]

Method #1:

    private static Color IntToColorWithAplphaFF(int i)
    {
        return Color.FromArgb(0xFF, Color.FromArgb(i));
    }

Method #2:

    private static Color IntToColorWithAplphaFF2(int i)
    {
        return Color.FromArgb(i | ((0xFFFFFF - i + 1)*-1));
    }