Wait for the gel image to open.
Ask the user to draw a rectangle around the gel.
Get the coordinates of the Region of Interest (ROI) of the gel.
Check if a valid ROI has been selected.
If a valid ROI has been selected, perform the following actions:
a. Select the ROI in the image.
b. Calculate the mean intensity value within the ROI.
c. Check if the mean intensity value is valid.
d. If the mean intensity value is valid, normalize the image by dividing it by the mean value.
e. Enhance the contrast of the normalized image and display it.
f. Create a copy of the original gel image.
g. Ask the user to select the bands of interest in the normalized gel.
h. Store the coordinates of the selected bands.
i. Display the selected bands on the graph.
j. Calculate and display the normalized intensity profile for each selected band.
k. Save the original gel image, the graph, and the normalized image to files.
l. Display a success message indicating that the files have been saved.

If a valid ROI has not been selected, display an error message.
If the mean intensity value is zero or negative, display an error message.
If no valid bands of interest have been selected, display an error message.

In summary, this program automates the processing of gel images, normalizes the intensity of the image, allows the user to select and analyze bands of interest, and saves the results to files.