Color.FromArgb Method (Int32, Int32, Int32, Int32)

 

Creates a Color structure from the four ARGB component (alpha, red, green, and blue) values. Although this method allows a 32-bit value to be passed for each component, the value of each component is limited to 8 bits.

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

public static Color FromArgb(
	int alpha,
	int red,
	int green,
	int blue
)

Parameters

alpha
Type: System.Int32

The alpha component. Valid values are 0 through 255.

red
Type: System.Int32

The red component. Valid values are 0 through 255.

green
Type: System.Int32

The green component. Valid values are 0 through 255.

blue
Type: System.Int32

The blue component. Valid values are 0 through 255.

Return Value

Type: System.Drawing.Color

The Color that this method creates.

Exception Condition
ArgumentException

alpha, red, green, or blue 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 PaintEventArgse, which is a parameter of the Paint event handler. The code performs the following actions:

  • Creates three brushes, each a different color. Each Color structure that is used to create a brush is created from four component values (alpha, red, green, blue).

  • Uses an imaginary triangle to position three circles.

  • Paints three overlapping circles, each centered on one vertex of the triangle, using a different brush for each circle.

public void FromArgb1(PaintEventArgs e)
{
    Graphics     g = e.Graphics;

    // Transparent red, green, and blue brushes.
    SolidBrush trnsRedBrush = new SolidBrush(Color.FromArgb(120, 255, 0, 0));
    SolidBrush trnsGreenBrush = new SolidBrush(Color.FromArgb(120, 0, 255, 0));
    SolidBrush trnsBlueBrush = new SolidBrush(Color.FromArgb(120, 0, 0, 255));

    // Base and height of the triangle that is used to position the
    // circles. Each vertex of the triangle is at the center of one of the
    // 3 circles. The base is equal to the diameter of the circles.
    float   triBase = 100;
    float   triHeight = (float)Math.Sqrt(3*(triBase*triBase)/4);

    // Coordinates of first circle's bounding rectangle.
    float   x1 = 40;
    float   y1 = 40;

    // Fill 3 over-lapping circles. Each circle is a different color.
    g.FillEllipse(trnsRedBrush, x1, y1, 2*triHeight, 2*triHeight);
    g.FillEllipse(trnsGreenBrush, x1 + triBase/2, y1 + triHeight,
        2*triHeight, 2*triHeight);
    g.FillEllipse(trnsBlueBrush, x1 + triBase, y1, 2*triHeight, 2*triHeight);
}

.NET Framework
Available since 1.1
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