How to remove a percentage of image counting from the bottom to top

Hi

I want to subtract a portion of image (e.g. 30% of it from the top). How do I do that?

If I do, something like this,

img = (croppedImage - (croppedImage.*0.3));

I usually get a 30% deduction from the bottom of it. I want this deduction to be from the top.

Moreover, I need a method to translate the deduction to number of rows. To be known, how many pixel rows this 30% of the image is.

Any ideas please?

[Rik]

Do you want to change the size of your image, or the ensities that make up that image?

Answer 1

[Mark Sherstan]

Look at the example I wrote for you below. Use the size function and realize that imcrop takes an array in the form of [xPosition yPosition width height] where the (0,0) point is the top left corner of your image.

I = imread('test.png');
[height width dims] = size(I);

J = imcrop(I,[0 floor(height*0.3) width height-floor(height*0.3)]);

figure(1)
subplot(1,2,1); imshow(I)
subplot(1,2,2); imshow(J)

[Stelios Fanourakis]

It needed some editing in order to fit to my code but it worked just fine. Thank you so much Mark.

May you know a way of how to find the number of rows this 30% deduction is from the top of the image?

[Mark Sherstan]

Glad it worked! You could do something along the lines of this:

I = imread('test.png');
[height width dims] = size(I);
rows30 = floor(height*0.3) % I used floor but you can use ceil, round, etc...

[Stelios Fanourakis]

Thank you so much Mark once again.