Abstract: This study introduces the histogram thresholding approaches, explains its principals, advantages and disadvantages, and its uses. Thresholding is one of the old, simple and popular techniques for image segmentation. Here, three different thresholding algorithms are examined. These are global thresholding, adaptive thresholding and global adaptive thresholding methods. The effects of the examined thresholding methods and segmentation yields are compared with an application based on computer simulations over uneven illuminated images.