our concluding example uses gray-scale reconstruction in seceral steps. the objective is to isolate the text out of the image of calculator keys shown in fig. 9.30(a). the first step is to suppress the horizontal reflections along the top of each key. to accomplish this, we take advantage of the fact that these reflection are wider than any single text character in image. we perform opening-by-reconstruction using a structuring element that is a long horizontal line: