Threshold Tab (Histogram Dialog Box)

Use this tab to convert a grayscale or color image to a simpler black and white bitonal image. This operation can be used to isolate features in an image. For example, you can isolate the contour lines from a grayscale scan of a USGS map.

After the grayscale or color image is converted to a bitonal image, you can use the vectorization tools to convert the raster objects to vectors.

Threshold

Displays which pixels are black and which pixels are white. After you move the slider, all pixels to the left of the slider become black and all pixels to the right of the slider become white.

Apply

Converts the selected grayscale or color image to a black and white bitonal image.

Preview

Displays a preview of the image showing the modifications.

Click an image name to view the preview for that image. Histogram changes apply to all images you have selected, not just to the image that is currently previewed.

This preview does not show any display-only adjustments you may have made to the image using the AutoCAD IMAGEADJUST command. If you apply changes to the image using the Histogram, then all display-only adjustments are reset to the defaults.