1. A method of measuring a thickness, the method comprising: obtaining an original image of a structure, the structure including a first layer, the first layer including a first boundary and a second boundary, the original image including an image of the structure having the first layer, the second boundary being substantially indistinguishable in the original image; extracting the first boundary of the first layer in the original image; converting the original image into a first image based on the extracted first boundary; generating a second image, based on filtering the first image; extracting the second boundary of the first layer in the second image; and calculating a thickness of the first layer based on the extracted second boundary in the second image.