Cropping imagesc with a handler and rect

Hello!

I'm currently working on a project which requires me to crop detected objects out of frames of images. X,Y coordinates are already obtained automatically.

The frame can only be displayed using imagesc instead of imshow.

I would like to crop but imcrop requires the frame to be saved as an image first. However, when I save the imagesc as an image file and reopen it for cropping, the X and Y coordinates of the objects to be cropped have changed.

%% Display frame with detected objects, only 2 images detected is sufficient 
z=1 %frame number
       bin_image{z}
       handler = imagesc(bin_image{z}.frame);
       hold on;
       x1=bin_image{z}.x(1); %coordinates of object detected
       x2=bin_image{z}.x(2);
       x3=bin_image{z}.x(3);
       x4=bin_image{z}.x(4);

       y1=bin_image{z}.y(1);
       y2=bin_image{z}.y(2);
       y3=bin_image{z}.y(3);
       y4=bin_image{z}.y(4);

       rectangle('Position',[x1 y1 x2-x1 y2-y1],'EdgeColor','r');
       rectangle('Position',[x3 y3 x4-x3 y4-y3],'EdgeColor','r');
  
     
       saveas(handler,sprintf('Savedframe%d.png',z));
       hold off;

Imagesc coordinates:

x: [205 216 223 234 0 0 0 0 0 0 0 0 0 0 0 0]

y: [91 108 91 108 0 0 0 0 0 0 0 0 0 0 0 0]

num_obj: 2

By manually crop and trial and error, i realised that the corrdinates of x and y of the two objects have changed when I want to crop out the two objects. How do I avoid the change in coordinates, because I would like to automate this process if given a few hundred frames to crop out from? Thank you!

   %% Crop Rectangles       
        I = imread('SavedFrame1.png');
        J = imcrop(I,[590 318 201 69]);
        handler2 = imshow(J);
        saveas(handler2,sprintf('SavedCrop1.png'));   

[Image Analyst]

"imcrop requires the frame to be saved as an image first" well, don't you HAVE images? If not, what do you have? Isn't bin_image{z}.frame an image? If not, exactly what is it?

[WILSON XU WEIXUAN]

Oh sorry I just realised it is an image. My bad.

I have added the cropping code inside, but SavedCrop1 instead produced the same image as the Savedframe1.

Sorry but Am I still missing out on something?

SavedCrop1:

Savedframe1:

%% Display frame with detected objects, only 2 images detected is sufficient 
z=1 %frame number
       bin_image{z}
       handler = imagesc(bin_image{z}.frame);
       hold on;
       x1=bin_image{z}.x(1); %coordinates of object detected
       x2=bin_image{z}.x(2);
       x3=bin_image{z}.x(3);
       x4=bin_image{z}.x(4);
       y1=bin_image{z}.y(1);
       y2=bin_image{z}.y(2);
       y3=bin_image{z}.y(3);
       y4=bin_image{z}.y(4);
       rectangle('Position',[x1 y1 x2-x1 y2-y1],'EdgeColor','r');
       rectangle('Position',[x3 y3 x4-x3 y4-y3],'EdgeColor','r');
  
       saveas(handler,sprintf('Savedframe%d.png',z));
       
       J = imcrop(bin_image{z}.frame,[x1 x2 x2-x1 y2-y1]);
       handler2 = imshow(J);
       saveas(handler2,sprintf('SavedCrop1.png'));
       
       
       hold off;

Answer 1

[Image Analyst]

You should be saving the images bin_image{z}.frame and "J" directly with imwrite() instead of saving the figure windows with saveas().