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Color.FromArgb Method (Int32, Color)

Creates a Color structure from the specified Color structure, but with the new specified alpha value. Although this method allows a 32-bit value to be passed for the alpha value, the value is limited to 8 bits.

Namespace:  System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

public static Color FromArgb(
	int alpha,
	Color baseColor
)

Parameters

alpha
Type: System.Int32
The alpha value for the new Color. Valid values are 0 through 255.
baseColor
Type: System.Drawing.Color
The Color from which to create the new Color.

Return Value

Type: System.Drawing.Color
The Color that this method creates.

ExceptionCondition
ArgumentException

alpha is less than 0 or greater than 255.

To create an opaque color, set alpha to 255. To create a semitransparent color, set alpha to any value from 1 through 254.

The following code example is designed for use with Windows Forms, and it requires PaintEventArgs e, which is a parameter of the Paint event handler. The code performs the following actions:

  1. Creates Color structures from the three color component values (red, green, blue). Three Color structures are created, one for each primary color.

  2. Iterates through a range of alpha values, changing the alpha value of a color.

  3. During each iteration, sets the color of a brush to the modified color and paints a rectangle to show the color.

  4. Repeats steps 2 and 3 for each primary color.

The alpha value is never fully opaque and the rectangles overlap so you get color-combination effects.


public void FromArgb3(PaintEventArgs e)
{
    Graphics     g = e.Graphics;

    // Opaque colors (alpha value defaults to 255 -- max value).
    Color red = Color.FromArgb(255, 0, 0);
    Color green = Color.FromArgb(0, 255, 0);
    Color blue = Color.FromArgb(0, 0, 255);

    // Solid brush initialized to red.
    SolidBrush  myBrush = new SolidBrush(red);
    int alpha;

    // x coordinate of first red rectangle
    int x = 50;         

    // y coordinate of first red rectangle
    int y = 50;         

    // Fill rectangles with red, varying the alpha value from 25 to 250.
    for (alpha = 25; alpha <= 250; alpha += 25)
    {
        myBrush.Color = Color.FromArgb(alpha, red);
        g.FillRectangle(myBrush, x, y, 50, 100);
        g.FillRectangle(myBrush, x, y + 250, 50, 50);
        x += 50;
    }
    // x coordinate of first green rectangle
    x = 50;             

    // y coordinate of first green rectangle
    y += 50;            

    // Fill rectangles with green, varying the alpha value from 25 to 250.
    for (alpha = 25; alpha <= 250; alpha += 25)
    {
        myBrush.Color = Color.FromArgb(alpha, green);
        g.FillRectangle(myBrush, x, y, 50, 150);
        x += 50;
    }
    // x coordinate of first blue rectangle.
    x = 50; 

     // y coordinate of first blue rectangle
    y += 100;           


    // Fill rectangles with blue, varying the alpha value from 25 to 250.
    for (alpha = 25; alpha <= 250; alpha += 25)
    {
        myBrush.Color = Color.FromArgb(alpha, blue);
        g.FillRectangle(myBrush, x, y, 50, 150);
        x += 50;
    }
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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