Image segmentation determining method, gesture determining method, image sensing system and gesture determining system

An image segmentation threshold value determining method, comprising: defining a plurality of image regions of a first sensing image; determining a first, a second part image segmentation threshold values according to a first, second image regions of the image regions; performing a first, a second image segmentation operation to the first sensing image according to the first, the second part image segmentation threshold values to acquire a first, a second segmented images; and determining which one of the first, the second part image segmentation threshold values should be a first image segmentation threshold value of an image processor according to the first, the second segmented images.