The simplest technique for segmenting an image is to pick a threshold pixel value. All pixels with grey-scale values below the threshold are assigned as object pixels, while all pixels with values above the threshold are assigned as background pixels. This technique is called binary thresholding or hard thresholding.
The following figure shows an idealized scene, the application of a hard threshold, and the resulting segmentation of the image into object and background pixels. In the example below, a threshold value of 150 was used. All pixels with values greater than or equal to 150 are treated as background; all pixels with values less than 150 are treated as object.
