1. Using the examples presented for displaying an image in Matlab together with those for accessing pixel locations, investigate adding and subtracting a scalar value from an individual location, i.e. I(i, j) = I(i, j) + 25 and I(i, j) = I(i, j) - 25 . Start by using the grayscale 'cell.tif' example image and pixel location I(100,20). What is the effect on the greyscale color of adding and subtracting?

2. Based on your answer to Question 1, use the "for" construct in Matlab to loop over all the pixels in the image and brighten or darken the image.