The so-called threshold, also known

The so-called threshold, also known as the critical value, refers to the lowest or highest value that an effect can produce. Thresholds are used in many places, such as automatic control systems, biological sciences, mathematics, and earthquake engineering. Here we talk about the gray threshold, refers to the gray image or color image into a high contrast black and white image. Take a certain color level as the threshold value, the pixels brighter than the threshold value will be converted to white, otherwise it will be converted to black.Gray threshold segmentation is to divide the image gray into different levels, and then determine the gray, threshold method. In fact, gray threshold segmentation is binarization, that is to choose a threshold to convert the image into black and white binary image for image segmentation and edge extraction. Obviously, image thresholding is a ladder function, which belongs to the nonlinear operation of image gray level. The curve of the transformation function is shown in the figure. Its function is to specify a threshold value by the user. If the gray value of a pixel in the image is greater than the threshold value, the gray value of the pixel will be set to 255, otherwise the gray value will be set to 0.