How to Crop A bunch of image with same box but different position

Hi ,

I'm trying to cropping polygons out of a bunch of images where the polygon's dimention and shape is always the same but I can choose the position changing the center or a vertex. I already made a code that allow me to do this with a rectangle but i want to change the shape. Anyone can help me please?

figure
imshow(read(DatabaseTest , i))
hold on
[x0,y0] = ginput(1);

J = imadjust(rgb2gray(read(DatabaseTest , i)));
ImageTest = imcrop(J,[x0 - width / 2,y0 - height / 2,width,height]);

this is a part of a code able to extract HOG Features so I change rgb2gray to reduce noise effects (if you want you can also suggest me any tips).

Answer 1

[Ani Singh]

You can do this by using roipoly function.

for ore infor see : https://www.mathworks.com/help/images/ref/roipoly.html

I am attaching sample script for it :

% read the image
input = imread (I)
%Co-ordinates of selected area(change thee according to your requirements)
r=[40 204 267 102];
c=[136 125 210 219];
BW=roipoly(input,r,c);
%replacing white area with the desired image
out=zeros(size(BW,1),size(BW,2));
out = gray .* uint8(BW); %store those pixels in output which are selected, can be done by 2 for loops also
imshow(out)

[Martino Corno]

Thanks very much,

I understood what this code want to performe but 'BW' and 'gray' are not the same class of integer . I copied and pasted your code, but the matrix moltiplication doesn't seems to work for my case, I also change with function uint8 the class of matrix 'gray' but it doesn't work as well . Do you have any suggestion?