MATLAB crop image and make more blue not displaying change - image

Question

In Matlab, I am trying to crop an image and be able to manipulate in some way (I adjusted contrast) and show change in formatting as its displayed beside the original image (by making it turn more and more blue).
The code runs successfully, but it seems to already have made the cropped image as blue as the for loop would take it.
How can I edit the code so that as the original is displayed beside the cropped, the cropped image is showing the change in formatting of turning more and more blue?
Here's what I have so far:
I = imread('peppers.png');
I2 = imcrop(I);
I3 = imadjust(I2,[.2 .3 0; .6 .7 1],[]);
subplot(1,2,1), subimage(I);
for i = 1:0.1:7
I3(:,:,3) = I3(:,:,3) + i;
subplot(1,2,2), subimage(I3)
end
To understand what is meant by showing an image to turn more and more blue upon display, please run:
img = imread('peppers.png');
for i = 1:0.1:7
figure(1)
img(:,:,3) = img(:,:,3) + i;
imshow(img)
end

Answer 1

If I understand what you want correctly, you want to display the original image on the left, and the bluer image on the right, and showing it progressively going blue as the loop is iterating. What I suggest you do is pause at each iteration in the loop to give you time to see the results. You can also put a title that shows what value i is at each iteration before the image changes. Also, make sure you add a drawnow command before you pause to flush the buffer so that you can visualize the results immediately. In other words, try this:
I = imread('peppers.png');
I2 = imcrop(I);
I3 = imadjust(I,[.2 .3 0; .6 .7 1],[]);
figure;
subplot(1,2,1);
subimage(I);
for i = 1:0.1:7
I3(:,:,3) = I3(:,:,3) + i;
subplot(1,2,2);
subimage(I3);
title(num2str(i)); %// Change - add title
drawnow; %// Change - flush buffer
pause(0.3); %// Change - add a pause
end
You should see the change in the blue channel for each value of i every 0.3 seconds. Change the value of 0.3 according to your tastes. BTW, the image is uint8, so adding floating point values to the blue channel will have no effect as these values will be truncated. Only integer values will show something appreciable.