ImageAttributes.ClearThreshold Method (ColorAdjustType)
Clears the threshold value for a specified category.
Assembly: System.Drawing (in System.Drawing.dll)
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 0.7x55, 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 different 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 threshold and a gamma value for the default category. If you set the threshold for the pen category by calling the SetThreshold method, the default threshold will not apply to pens. If you later clear the pen threshold by calling the ClearThreshold method, the pen category will not revert to the default threshold; rather, the pen category will have no threshold. Similarly, the pen category will not revert to the default gamma value; rather, the pen category will have no gamma value.
Available since 1.1