Finish the thresholding function
This function only supplies the gray level image. It means that when a image will be applied this function, it should be translated to gray level image
Add CheckBox to check whether we want to apply the thresholding function
Add TrackBar to change the threshold value
Change some procedure of thresholding
When the value of CheckBox that apply thresholding is false, show the original image.
Let the result contain the original image and the gray level image.
Merge branch 'thresholding'