Image snip and paste. Draw a polygone on an image, then click and drag to move that part of the image around. Bonus points for resize and rotate.

Hi,

I'm essentially trying to recreate the functionality of the select tool in MS Paint, but using a polygone rather than a rectangle. I want the user to load an image, draw a polygone over the image, then click and drag that polygone to cut that section out of the image and move it somewhere else.

bonus points, as later I want the user to be able to resize and rotate that polygone. Also place mutiple polygons moving different parts of the same image.

Below is the best code I have so far. It loads tire.jpg but feel free to swap that for any other image.

The user can select and draw the polygone, the commented out lines of code after defining the polygon_mask test that the image is cut from original image in the shape of the polygone correctly. Which it is. That works fine.

The function roi_moving seems to work well too. Dragging the cut section of image within the polygone, and a black section is left behind at the polygones orignal location.

roi_moved seems to be the problem. It doesn't paste the polygone down after the user has finished moving it. So I tried using the code from roi_moving at the end of roi_moved as shown at the bottom but that didn't work.

I also tried a whole seperate approach using addlistener functions.

Finally I've tried asking ChatGPT but to no avail.

I'm also getting the below warning message coming from MATLAB.

Error Message: (shows as code, it's actually orange error text from the command window.

> In images.roi.internal/ROI/dragROI
In images.roi.internal.ROI 
Warning: Error occurred while executing the listener callback for event MovingROI defined for class images.roi.Polygon:
Unable to perform assignment because the left and right sides have a different number of elements.

Error in test3>roi_moving (line 52)
    new_image(repmat(new_polygon_mask, [1, 1, size(I, 3)])) = I(repmat(temp_mask, [1, 1, size(I, 3)]));

Error in test3>@(src,event)roi_moving(src,event,h_image,I) (line 28)
lh_moving = addlistener(h, 'MovingROI', @(src, event)roi_moving(src, event, h_image, I));

Error in images.roi.internal.ROI/dragROI

Error in images.roi.internal.ROI 
> In images.roi.internal/ROI/dragROI
In images.roi.internal.ROI 

%The best code I have so far.

% this is really close. It moves the image but doesn't drop it off where it should be

I = imread('tire.jpg');
figure;
h_image = imshow(I);
hold on;

% Allow the user to create and move polygonal ROIs
h = drawpolygon;
if ~isvalid(h)
    return
end
pos = h.Position;

% Round the position values to integers for indexing
pos_int = round(pos);

% Generate a mask from the polygon
polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(I, 1), size(I, 2));

% % Create an image section from the polygon
% section = I(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)), :);
% figure
% h_section = imshow(section); % show rectancle of outer edge of polygone
% set(h_section, 'AlphaData', polygon_mask(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)))); %show polygone only

% Set up listeners for the MovingROI and ROIMoved events
lh_moving = addlistener(h, 'MovingROI', @(src, event)roi_moving(src, event, h_image, I));
lh_moved = addlistener(h, 'ROIMoved', @(src, event)roi_moved(src, event, h_image, I));

% Callback function for when the ROI is moving
% Callback function for when the ROI is moving
function roi_moving(src, ~, h_image, I)
    % Get the current position of the polygon
    pos = src.Position;
    
    % Round the position values to integers for indexing
    pos_int = round(pos);
    
    % Generate a mask from the new polygon position
    new_polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(I, 1), size(I, 2));
    
    % Get the old polygon_mask
    old_polygon_mask = src.UserData;
    
    % Create a new mask of the same size as I
    temp_mask = false(size(I, 1), size(I, 2));
    temp_mask(1:size(old_polygon_mask, 1), 1:size(old_polygon_mask, 2)) = old_polygon_mask;
    
    % Create a new image with the section cut from the original image
    new_image = I;
    new_image(repmat(new_polygon_mask, [1, 1, size(I, 3)])) = I(repmat(temp_mask, [1, 1, size(I, 3)]));
    new_image(repmat(temp_mask, [1, 1, size(I, 3)])) = 0;
    
    % Update the displayed image
    set(h_image, 'CData', new_image);
end


% Callback function for when the ROI has been moved
function roi_moved(src, ~, h_image, I)
    % Get the current position of the polygon
    pos = src.Position;
    
    % Round the position values to integers for indexing
    pos_int = round(pos);
    
    % Generate a mask from the new polygon position
    new_polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(I, 1), size(I, 2));
    
    % Store the new_polygon_mask in the ROI's UserData property
    src.UserData = new_polygon_mask;
    
    % Update the displayed image
    set(h_image, 'CData', I);
end

Modified roi_moved:

% Callback function for when the ROI has been moved
function roi_moved(src, ~, h_image, I)
    % Get the current position of the polygon
    pos = src.Position;
    
    % Round the position values to integers for indexing
    pos_int = round(pos);
    
    % Generate a mask from the new polygon position
    new_polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(I, 1), size(I, 2));
    
        % Get the old polygon_mask
    old_polygon_mask = src.UserData;
    
    % Create a new mask of the same size as I
    temp_mask = false(size(I, 1), size(I, 2));
    temp_mask(1:size(old_polygon_mask, 1), 1:size(old_polygon_mask, 2)) = old_polygon_mask;
    
    % Create a new image with the section cut from the original image
    new_image = I;
    new_image(repmat(new_polygon_mask, [1, 1, size(I, 3)])) = I(repmat(temp_mask, [1, 1, size(I, 3)]));
    new_image(repmat(temp_mask, [1, 1, size(I, 3)])) = 0;
    
    % Update the displayed image
    set(h_image, 'CData', new_image);
end

Answer 1

[Image Analyst]

See attached copy and paste demos.

[Gregory Smith]

Hi thank you that was super helpfull but I'm still now quite there.

I used your copy_paste_image code, and modified it to use drawpolygon to create a polygone. That all works, it extracts the image from under the polygone and draws that into a subplot. then I get stuck here.

pos_int are the corner or a rectangle around the polygone.

x and y are then mouse click points.

So I'm just shifting the polygone by values relative to the mouse click.

the new location of the polygone is within the image bounds.

However, originalImage(polygon_mask_new) = originalImage(polygon_mask) flags and error Unable to perform assignment because the left and right sides have a different number of elements. So I checked the size of my polygon's and they're different. How can that be? Is it rounding somewhere?

polygon_mask_new = poly2mask(pos_int(:,1)+x, pos_int(:,2)-y, size(originalImage, 1), size(originalImage, 2));

sum(polygon_mask_new,"all") % 58376

sum(polygon_mask,"all") % 58419

originalImage(polygon_mask_new) = originalImage(polygon_mask);

[Image Analyst]

I don't know just from looking at this snippet you included. Please attach the whole m-file with the paperclip icon.

[Gregory Smith]

Here is the code:

Thank you so much for your help!

% Lets user drag out a box on an image, then define where they want to paste it.
% Then it pastes the drawn region onto the original image.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;
format compact;

poly = true; % polygon or square

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
	% User does not have the toolbox installed.
	message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
	reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
	if strcmpi(reply, 'No')
		% User said No, so exit.
		return;
	end
end

fullFileName = ('tire.jpg');

% Read in the image.  It can be either color or gray scale.  Demo can handle either case.
[originalImage, storedColorMap] = imread(fullFileName);

% Get the dimensions of the image.
% numberOfColorBands should be = 1.

% If the image is floating point, like the 'HotCoffee.tif' thermal demo image,
% convert it to uint8.
if isa(originalImage, 'single') || isa(originalImage, 'double')
	originalImage = uint8(255 * mat2gray(originalImage));
end

% If the image is an indexed image, turn it into a RGB color image.
if ~isempty(storedColorMap)
	originalImage = ind2rgb(originalImage, storedColorMap);
	fprintf('%s is an indexed image. I will convert it to an RGB color image.');
end

% Get the dimensions (size) of the image in all directions.
[rows, columns, numberOfColorBands] = size(originalImage);
fprintf('%s is %d rows by %d columns by %d color channels.\n', rows, columns, numberOfColorBands);

% Display the original image.
hFig = figure;
subplot(2, 2, 1);
imshow(originalImage);
axis on;
drawnow;
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')



% Ask user to draw a box.
subplot(2, 2, 1);
if poly == false
    promptMessage = sprintf('Drag out a box that you want to copy,\nor click Cancel to quit.');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
    if strcmpi(button, 'Cancel')
    	close(hFig); % Close down the figure - get rid of it.
    	return;
    end

    k = waitforbuttonpress;
    point1 = get(gca,'CurrentPoint');    % button down detected
    finalRect = rbbox;                   % return figure units
    point2 = get(gca,'CurrentPoint');    % button up detected
    point1 = point1(1,1:2);              % extract x and y
    point2 = point2(1,1:2);
    p1 = min(point1,point2);             % calculate locations
    offset = abs(point1-point2);         % and dimensions
    % Find the coordinates of the box.
    xCoords = [p1(1) p1(1)+offset(1) p1(1)+offset(1) p1(1) p1(1)];
    yCoords = [p1(2) p1(2) p1(2)+offset(2) p1(2)+offset(2) p1(2)];
    x1 = round(xCoords(1));
    x2 = round(xCoords(2));
    y1 = round(yCoords(5));
    y2 = round(yCoords(3));
    width = x2-x1;
    height = y2-y1;

    hold on
    axis manual
    plot(xCoords, yCoords, 'b-'); % redraw in dataspace units

    % Display the cropped image.
    % croppedImage = grayImage(y1:y2,x1:x2); % For gray scale image only, you can use indexing instead of imcrop().
    croppedImage = imcrop(originalImage, [x1, y1, width, height]);
    subplot(2, 2, 3);
    imshow(croppedImage);
    axis on;
    title('Region that you defined', 'FontSize', fontSize);

    % Paste it onto the original image
    [rows2, columns2, numberOfColorBands2] = size(croppedImage);
    fprintf('The copied rectangle is %d rows by %d columns by %d color channels\n', rows2, columns2, numberOfColorBands2);
    promptMessage = sprintf('In the UPPER LEFT IMAGE,\nClick on the upper left point where you want to paste it,\nor click Cancel to quit.');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
    if strcmpi(button, 'Cancel')
    	close(hFig); % Close down the figure - get rid of it.
    	return;
    end
    [x, y] = ginput(1);
    % Determine the pasting boundaries.  Clip the image if it goes outside the original image.
    r1 = int32(y);
    c1 = int32(x);
    r2 = r1 + rows2 - 1;
    r2 = min([r2 rows]);
    c2 = c1 + columns2 - 1;
    c2 = min([c2, columns]);
    fprintf('The target rectangle is from row %d to row %d, and from column %d to column %d.\n', r1, r2, c1, c2);
    %plot([c1, c2, c2, c1, c1], [r1, r1, r2, r2, r1], 'r-'); %why are 5 dots needed for a square?
    plot([c1, c2, c2, c1], [r1, r1, r2, r2], 'r-')
    % Paste as much of croppedImage as will fit into the original image.
    originalImage(r1:r2, c1:c2, :) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1), :);
    subplot(2, 2, 4);
    imshow(originalImage);
    axis on;
    title('Region that you defined pasted onto original', 'FontSize', fontSize);


else

    h = drawpolygon;
    if ~isvalid(h)
        return
    end
    pos = h.Position;
    pos_int = pos;

    % Generate a mask from the polygon
    polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(originalImage, 1), size(originalImage, 2));


    % % Create an image section from the polygon
    croppedImage = originalImage(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)), :);
    subplot(2, 2, 3);
    h_section = imshow(croppedImage); % show rectancle of outer edge of polygone
    set(h_section, 'AlphaData', polygon_mask(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)))); %show polygone only
    axis on;
    title('Region that you defined', 'FontSize', fontSize);

    rows2 = min(pos_int(:,2)); %corner of rectangle containing the polygone
    columns2 = min(pos_int(:,1));%corner of rectangle containing the polygone

    fprintf('The copied rectangle is %d rows by %d columns by %d color channels\n', rows2, columns2);
    promptMessage = sprintf('In the UPPER LEFT IMAGE,\nClick on the upper left point where you want to paste it,\nor click Cancel to quit.');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
    if strcmpi(button, 'Cancel')
    	close(hFig); % Close down the figure - get rid of it.
    	return;
    end
    [x, y] = ginput(1);
    r1 = int32(y);
    c1 = int32(x);
    
    r2 = r1 + rows2 - 1;
    r2 = min([r2 rows]);
    c2 = c1 + columns2 - 1;
    c2 = min([c2, columns]);

    %plot([c1, c2, c2, c1, c1], [r1, r1, r2, r2, r1], 'r-');
    % Paste as much of croppedImage as will fit into the original image.
    %originalImage(r1:r2, c1:c2, :) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1), :);
    % new mask location
    
    subplot(2, 2, 2);
    imshow(polygon_mask_new)

    polygon_mask_new = poly2mask(pos_int(:,1)+x, pos_int(:,2)-y, size(originalImage, 1), size(originalImage, 2));
    sum(polygon_mask_new,"all")  % 58376
    sum(polygon_mask,"all")      % 58419

    originalImage(polygon_mask_new) = originalImage(polygon_mask);

    subplot(2, 2, 4);
    imshow(originalImage);
    axis on;
    title('Region that you defined pasted onto original', 'FontSize', fontSize);
end




% Paste it onto the original image
[rows2, columns2, numberOfColorBands2] = size(croppedImage);
fprintf('The copied rectangle is %d rows by %d columns by %d color channels\n', rows2, columns2, numberOfColorBands2);
promptMessage = sprintf('In the UPPER LEFT IMAGE,\nClick on the upper left point where you want to paste it,\nor click Cancel to quit.');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
	close(hFig); % Close down the figure - get rid of it.
	return;
end
[x, y] = ginput(1);
% Determine the pasting boundaries.  Clip the image if it goes outside the original image.
r1 = int32(y);
c1 = int32(x);
r2 = r1 + rows2 - 1;
r2 = min([r2 rows]);
c2 = c1 + columns2 - 1;
c2 = min([c2, columns]);
fprintf('The target rectangle is from row %d to row %d, and from column %d to column %d.\n', r1, r2, c1, c2);
plot([c1, c2, c2, c1, c1], [r1, r1, r2, r2, r1], 'r-');
% Paste as much of croppedImage as will fit into the original image.
originalImage(r1:r2, c1:c2, :) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1), :);
subplot(2, 2, 4);
imshow(originalImage);
axis on;
title('Region that you defined pasted onto original', 'FontSize', fontSize);

[Image Analyst]

You tried to show the new polygon before you created it. Plus your new polygon is not the same size as the old one. Try using imtranslate to move the polygon mask to the desired position.

[Gregory Smith]

Hi,

I've updated the code and made some progress.

1) My understanding is that the listener should triggar roi_moved any time the polygone is moved on the image, this works if the user draws and then moves the polygone, but it doens't work if the user click on the polygone a second time and then wants to move it again.

Do you know how I can pass polygones in and out? - So a user can load in a polygone, move it, set it down. Draw and load in a 2nd polygone and move, resize that.

1) I solved the rounding issue sausing the polygons to be slights different sizes by using a loop. It's not ideal but seems to work. imtranslate Migh clean this up though, I'll take a look into that. Thank you.

2) I then have another loop to color the old polygone black. Do you know how I can form a unit8 polygone thats all black in a shape defined by CurrentPoly_Original_mask?

Thank you so much or your help.

clear all
clc

Tireimage = imread('tire.jpg');
figure;
h_image = imshow(Tireimage);
hold on;
axis on

% Allow the user to create and move polygonal ROIs
CurrentPoly_Original = drawpolygon;
if ~isvalid(CurrentPoly_Original)
    return
end
pos = CurrentPoly_Original.Position;

% Round the position values to integers for indexing
pos_int = round(pos);

% Generate a mask from the polygon
CurrentPoly_Original_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(Tireimage, 1), size(Tireimage, 2));

% % Create an image section from the polygon
% section = I(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)), :);
% figure
% h_section = imshow(section); % show rectancle of outer edge of polygone
% set(h_section, 'AlphaData', polygon_mask(min(pos_int(:,2)):max(pos_int(:,2)), min(pos_int(:,1)):max(pos_int(:,1)))); %show polygone only

% Set up listeners for the MovingROI and ROIMoved events
src = CurrentPoly_Original;
%lh_moving = addlistener(CurrentPoly_Original , 'MovingROI', @(src, event)roi_moving(src, event, h_image, Tireimage, CurrentPoly_Original_mask));
lh_moved = addlistener(CurrentPoly_Original , 'ROIMoved', @(src, event)roi_moved(src, event, h_image, Tireimage, CurrentPoly_Original_mask));

% Callback function for when the ROI has been moved
function [src] = roi_moved(src, ~, h_image, Tireimage, CurrentPoly_Original_mask)
    
    % Get the new position of the polygon
    pos = src.Position;
    
    % Round the position values to integers for indexing
    pos_int = round(pos);
    
    % Generate a mask from the new polygon position
    new_polygon_mask = poly2mask(pos_int(:,1), pos_int(:,2), size(Tireimage, 1), size(Tireimage, 2));
    
    [row1, col1] = find(CurrentPoly_Original_mask);
    [row2, col2] = find(new_polygon_mask);

    % Calculate the number of elements to copy
    num_elements = min(length(row1), length(row2));

    I_temp = Tireimage; % copy the original image.

    % replace the copy from location with black, might not want this.
    %Tireimage(CurrentPoly_Original_mask) = uint8([0,0,0]);
    for k = 1:num_elements
        Tireimage(row1(k), col1(k), :) = uint8([0,0,0]);
    end

    % copy and paste 1 pixel at a time
    for k = 1:num_elements
        Tireimage(row2(k), col2(k), :) = I_temp(row1(k), col1(k), :);
    end
    disp('image pasted')

    imshow(Tireimage)
    axis on
    hold on
    src = drawpolygon('Position', [src.Position(:, 1), src.Position(:, 2)]);
end

[Image Analyst]

2)

mask = uint8(CurrentPoly_Original_mask);

or am I not understanding something?