Code not showing desired outputs

I have written a code to identify the DNA bands and estimate their weight in a DNA gel electrophoresis image converted to grayscale. So, basically i am identifying the starting position of the column of the DNA band but here i am not getting the correct number and position of the column number where the white band occurs. Further after identification of the lanes i have counted the intensity of lanes and i identified the DNA ladder . So now the code asks for the reference weight of DNA ladder from the user and accordingly the weights of the rest of the DNA bands is displayed. But here i am not getting the correct starting point of the DNA band and also it shows error in line 87. Here is the image of the DNA gel and the i have uploaded the code in a file.