This documentation is archived and is not being maintained.

ImageAttributes.SetThreshold Method (Single, ColorAdjustType)

Sets the threshold (transparency range) for a specified category.

Namespace: System.Drawing.Imaging
Assembly: System.Drawing (in system.drawing.dll)

public void SetThreshold (
	float threshold,
	ColorAdjustType type
public void SetThreshold (
	float threshold, 
	ColorAdjustType type
public function SetThreshold (
	threshold : float, 
	type : ColorAdjustType
Not applicable.



A threshold value from 0.0 to 1.0 that is used as a breakpoint to sort colors that will be mapped to either a maximum or a minimum value.


An element of ColorAdjustType that specifies the category for which the color threshold is set.

Return Value

This method does not return a value.

The threshold is a value from 0 through 1 that specifies a cutoff point for each color component. For example, suppose the threshold is set to 0.7, and suppose you are rendering a color whose red, green, and blue components are 230, 50, and 220, respectively. The red component (230) is greater than 0.7x255, so the red component will be changed to 255 (full intensity). The green component (50) is less than 0.7x255, so the green component will be changed to 0. The blue component (220) is greater than 0.7x255, so the blue component will be changed to 255.

An ImageAttributes object maintains color and grayscale settings for five adjustment categories: default, bitmap, brush, pen, and text. For example, you can specify a threshold for the default category, a threshold for the bitmap category, and still a different threshold for the pen category.

The default color-adjustment and grayscale-adjustment settings apply to all categories that do not have adjustment settings of their own. For example, if you never specify any adjustment settings for the pen category, the default settings apply to the pen category.

As soon as you specify a color-adjustment or grayscale-adjustment setting for a certain category, the default adjustment settings no longer apply to that category. For example, suppose you specify a collection of adjustment settings for the default category. If you set the threshold for the pen category by passing Pen to the SetThreshold method, none of the default adjustment settings will apply to pens.

For a code example, see the SetThreshold(Single) method.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0