NIH Image

Enables and disables thresholding mode. Thresholding is used to segment an image into objects of interest and background on the bases of gray level. When thresholding is enabled, objects are displayed in black and background is white. The threshold is automatically set based on an analysis of the histogram of the current selection, or of the entire image if there is no selection. Background pixels will be ignored when making area and gray value measurements using the Measure and Analyze Particles commands. To vary the threshold, use the LUT tool and click and drag near the black/white boundary in the LUT window. As you vary the threshold, its value is continuously displayed in the Info window.

Use the Make Binary command to set all thresholded pixels to black and all background pixels to white. Use the wand tool to outline thresholded objects, and Analyze Particles to automatically measure objects segmented by thresholding. As a shortcut, you can enable thresholding by clicking on the stair step icon in the Map window. This shortcut, however, always sets the threshold to 128.