Image thresholding is a simple, yet effective, way of partitioning an image into a foreground and background. This image analysis technique is a type of image segmentation that isolates objects by converting grayscale images into binary images. Image thresholding is most effective in images with high levels of contrast.
For more detail, see Image Processing Toolbox.
See also: color profile, image analysis, image enhancement, image reconstruction, image segmentation, image transform, digital image processing, image processing and computer vision, Steve on Image Processing (blog), edge detection, image registration, affine transformation, lab color