1. A computer-implemented method for determining inflection points in an image of an object, the method comprising: (a) obtaining the image of the object from an image measuring machine; (b) performing binary image processing on a border of the image to obtain border points of the image of the object, and storing data of the border points in a storage device; (c) selecting a predetermined number of the border points to fit a straight line of the selected border points; (d) calculating a vertical distance between each selected border point and the straight line, summing each calculated distance to obtain a total distance, and executing step (e) if the total distance is less than a predetermined value, or executing step (f) if the total distance is greater than or equal to the predetermined value; (e) adding a new border point to the selected border points to fit a new straight line, and going to step (d); (f) regarding a last border point of the selected border points as an inflection point of the border of the object; and (g) sequentially selecting the predetermined number of other border points to fit another new straight line if a number of the residual border points is greater than or equal to the predetermined number, and returning to step (d).