Change the bottom-left half of the original image to a black right triangle.

I can change the whole picture to black, but i dont know how to change just a half like that. Please help! Thank you!!

Answer 1

[Matt J]

Hint:

triu(true(5,7))

ans = 5×7 logical array
   1   1   1   1   1   1   1
   0   1   1   1   1   1   1
   0   0   1   1   1   1   1
   0   0   0   1   1   1   1
   0   0   0   0   1   1   1

[Anna]

  x = imread('peppers.png'); imshow(x);
[r,c,s] = size(x);
y = x;
y(tril(true(r,c))) = 0;
imshow(y);

i just tried somehting like this, use tril(); but I wonder if do we have a way to select the correct diagonal of the rectangle as the figure shown in the problem?

[Matt J]

One possibility is to resize it with imresize() to make it square. Then, after blackening the lower triangle, restore the original size.