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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
)

Parameters

threshold
Type: System::Single

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.

type
Type: System.Drawing.Imaging::ColorAdjustType

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

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.

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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