How would I paste a cropped image onto a blank image of different size?

I created a blank image with a yellow background that is 200x200 pixel and also cropped 150x150 pixel image from another image. How would I go about pasting the the cropped 150x150 image onto the 200x200 image?

I tried to use pastedimg=combine(blankimg, croppedimg), which did not work and gave me the following error: "Subscripted assignment dimension mismatch".

Thank you in advancee for any help you can provide.

Answer 1

[Image Analyst]

Here's the second one of my copy and paste images demo. This one lets you select a box from the source image, and a destination on the destination image and it pastes it onto that location.

% 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;

% 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

% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'eight.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage);
axis on;
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')

% Let's compute and display the histogram, just for fun.
[pixelCount grayLevels] = imhist(grayImage);
subplot(2, 2, 2);
bar(pixelCount);
grid on;
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.

% Ask user to draw a box.
subplot(2, 2, 1);
promptMessage = sprintf('Drag out a box that you want to copy,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  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));
hold on
axis manual
plot(xCoords, yCoords, 'b-'); % redraw in dataspace units

% Display the cropped image.
croppedImage = grayImage(y1:y2,x1:x2);
subplot(2, 2, 3);
imshow(croppedImage);
axis on;
title('Region that you defined', 'FontSize', fontSize);

% Paste it onto the original image
[rows2 columns2] = size(croppedImage)
promptMessage = sprintf('Click on the upper left point where you want to paste it,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
[x, y] = ginput(1)
% Determine the pasting boundaries.
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.
grayImage(r1:r2, c1:c2) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1));
subplot(2, 2, 4);
imshow(grayImage);
axis on;
title('Region that you defined pasted onto original', 'FontSize', fontSize);

[integra-t]

Thanks, Image Analyst, your demos are great. However, I will not be able to use them for my homework assignment since our professor prefers to see all of our command history. I would not know where to begin if my professor asked me to explain all of the commands from your demos. Well maybe a part of it but still, I would be at a lost for words afterwards.

For now, I will stick to what Walter has provided.

[Image Analyst]

You will see Walter's code buried inside mine. It's the main line of code that does all the heavy lifting. The rest of my code is just all the other fancy stuff you might need to make a workable program such as reading in images and displaying them, letting the user specify where the areas to copy and paste are, etc. Doing this on a command line would be basically impractical. I'm pretty sure he'd let you do the same commands in a script. You could always use "echo on" to echo the script commands to the command window. And you wouldn't need to make your script as polished and fancy as mine - I tend to go overboard when making demos.

[integra-t]

Being that I am only a beginner at MatLab, it is hard to decipher what is important and what is not in your demo. Maybe you could point out what comes next in the code that Walter has been helping me with so far? Otherwise, I will wait until he chimes in again.

[Image Analyst]

My demos are almost always very well commented so beginners can follow them. If you look at my code, you see the line where I and Walter paste in the image. The next logical thing you might want to do is to display it. You'll see the call to subplot() in my code which tells it where on the screen to display the image, and the call to imshow() which actually does the display. You might want to put a title above it saying that this is the final output image, so that is what I did with the title() function. See - it's not that difficult if you just take it a line at a time. Not sure what you had in mind. If displaying the final image, like I did, is not what you had in mind, then tell me what you think should come next and I can give you code for that.

[integra-t]

I am very close to actually being finished just need to be able to display my croppedimg over the blankimg. As you can see from the image above, when I executed the commands from Walter, I ended with a blank white box in the blankimg instead. If you could help correct that, I would greatly appreciate it.

[Image Analyst]

If you're displaying A1 or A4, they are double's in the range of 0-255. I don't know why they ended up as doubles. See if you can prevent that. Otherwise cast to uint8 before display.

A1 = uint8(A1);
A4 = uint8(A4);

[integra-t]

After checking both images, it seems that I must have overlooked the fact that A1 was double and everything else was uint8. A1 was changed to uint8 and followed through with the rest of the commands from before and ended up with this picture that contains a blank image with a black background instead of my original yellow one.

http://db.tt/VLM4aYxs

[Image Analyst]

Okay, glad it's working. It is working isn't it?

[integra-t]

Unfortunately, it is not. After I changed A1 to uint8, that made it black. How would I keep it yellow after I change the image type?

[Image Analyst]

I've given you two sets of working code, which you don't want to use. Instead you ask us to fix your code which you haven't given us. How can we fix code we can't run or debug, and haven't even seen????

[integra-t]

My apologies Image Analyst. I thought that the Command History in the screenshots would suffice. Here is the code:

A1=ones(200,200,3);
A1(:,:,3)=0;
imshow(A1);
A2=imread('peppers.jpg');
A3=imcrop(A2,[0 0 150 150]);
imshow(A3);
A1=uint8(A1);
A4=A1;
A4(1:1+150-1,1:1+150-1,:)=A3;
imshow(A4)

[Image Analyst]

I didn't scroll over that far enough to see it. Besides I can't copy and paste from an image into the code editor. Edit your post, put a blank line in front of the code, highlight the code and click the {}Code icon so that it will look properly formatted. thanks. I fixed your code by avoiding floating point arrays and sticking to all uint8 arrays:

clc;    % Clear the command window.
clearvars;
workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;

% Create yellow canvass
rows = 200;
columns = 200;
% Make uint8 image not floating point.
A1 = 255 * ones(200,200,3, 'uint8');
A1(:,:,3) = 0;
subplot(2,2,1);
imshow(A1);
axis on;
title('A1 Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

% Read in original image.
A2=imread('peppers.png');
subplot(2,2,2);
imshow(A2);
axis on;
title('Original Color Image', 'FontSize', fontSize);

% Crop out a portion of it.
A3=imcrop(A2,[0 0 150 150]);
subplot(2,2,3);
imshow(A3);
axis on;
title('A3 Image', 'FontSize', fontSize);

% Paste cropped image onto canvass image.
A4(1:1+150-1,1:1+150-1,:)=A3;
% Display result.
subplot(2,2,4);
imshow(A4);
axis on;
title('A4 Image', 'FontSize', fontSize);

[integra-t]

It was just a matter of making sure all of the images were of uint8 format. I simplified your commands above since I have to show each step of my work to my professor. Just wanted to point one thing out that you seem to have missed in your code is A4=A1; which caused A3 Image to look exactly like A4 Image missing the yellow background.

Thank you again for all your help!

A1=255*ones(200,200,3, 'uint8');
A1(:,:,3)=0;
imshow(A1);
A2=imread('peppers.png');
figure, imshow(A2);
A3=imcrop(A2,[0 0 150 150]);
figure, imshow(A3);
A4=A1;
A4(1:1+150-1,1:1+150-1,:)=A3;
figure, imshow(A4);

Answer 2

[Walter Roberson]

pastedimg = blankimg;
pastedimg( startrow:startrow+150-1, startcol:startcol+150-1) = croppedimg;

[integra-t]

I just tried entering the last part of the command pastedimg(0:0+150-1, 0:0+150-1)=croppedimg and it gave me the following error, "Subscripts indices must be either real positive integers or logicals". I was hoping to paste the crop image on the left corner of the blankimg.

[Walter Roberson]

Your startrow and startcol would be 1 in that case. MATLAB indexing starts from 1.

[integra-t]

I just tried pastedimg(1:1+150-1, 1:1+150-1)=croppedimg and that led me to this error "Assignment has more non-singleton rhs dimensions than non-singleton subscripts".

[Walter Roberson]

pastedimg( startrow:startrow+150-1, startcol:startcol+150-1, :) = croppedimg;

[integra-t]

That command did not give me any errors but I still ended up with the exact same image as the one that I cropped earlier. Here is a link for the screenshot. http://db.tt/6CsArwsU

I feel like I am getting closer to the answer and really appreciate your help Walter!

[Walter Roberson]

Please check

size(blankimg)
size(croppedimg)

Did you remember to have the

pastedimg = blankimg;

line before the assignment of croppedimg ? I notice that I had a typoe (pastediomg) in my original above.

[integra-t]

I noticed the typo but ignored since I was using my own naming scheme for each of the images. The sizes of the images are listed below and I did remember to add in pastedimg = blankimg;.

size(A1) blankimg ans = 200 200 3 size(A3) croppedimg ans = 150 150 3

[Walter Roberson]

No, you have

A4=A3;

in your command history, but A3 is your cropped image. You need to set A4 to your blank image, A1.

[integra-t]

Thought you would not answer until tomorrow since its late. I am up late cause I have to work until 7AM. =D

Sorry, about the mix up. I associated the correct images with the proper corresponding name. Now I end up with a white box inside of the blank yellow image. http://db.tt/7JD332yK

Answer 3

[Image Analyst]

Here's one of my old demos. You should just be able to copy and past and run. It uses standard demo images.

clear
clc;
close all;
workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;

% Change the current folder to the folder of this m-file.
if(~isdeployed)
  cd(fileparts(which(mfilename)));
end
  
% 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

% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'Moon.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
bigGrayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(bigGrayImage);
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(bigGrayImage, []);
title('Original BIG 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') 

% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'cameraman.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
smallGrayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[smallRows smallColumns numberOfColorBands] = size(smallGrayImage);
% Display the original gray scale image.
subplot(2, 2, 2);
imshow(smallGrayImage, []);
title('Original SMALL Grayscale Image', 'FontSize', fontSize);
% Note: smallGrayImage could just have well been a sub-portion of
% another image that you extracted out with imcrop() or indexing.

% Paste small image into big one.
% Put upper left at xColumn = 50, and yRow = 100.
xColumn = 50;
yRow = 100;
row1 = yRow;
row2 = row1 + smallRows - 1;
col1 = xColumn;
col2 = col1 + smallColumns - 1;
% Not shown: making sure they don't exceed 
% image boundaries and making adjustments if they do.
pastedImage = bigGrayImage; % Initialize.
pastedImage(row1:row2, col1:col2) = smallGrayImage;
% Display the pasted gray scale image.
subplot(2, 2, 3);
imshow(pastedImage, []);
title('Pasted Image', 'FontSize', fontSize);

[Aminah Zhulaika]

hi image analyst, can I know how to use this code which can paste the cropped image on other picture instead of paste it on the original picture?

[Image Analyst]

@Aminah Zhulaika, Just initialize pasted image with your "other picture" instead of bigGrayImage:

pastedImage = otherImage; % Initialize.
pastedImage(row1:row2, col1:col2) = smallGrayImage;

or to do it in place, overwriting your original otherImage:

otherImage(row1:row2, col1:col2) = smallGrayImage;

[Aminah Zhulaika]

thank you. but this code cant select the region that I want to crop. How about the other code that you give before. This one. How to use this code which can paste the cropped image on other picture instead of paste it on the original picture?

% 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;

% 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

% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'eight.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage);
axis on;
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')

% Let's compute and display the histogram, just for fun.
[pixelCount grayLevels] = imhist(grayImage);
subplot(2, 2, 2);
bar(pixelCount);
grid on;
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.

% Ask user to draw a box.
subplot(2, 2, 1);
promptMessage = sprintf('Drag out a box that you want to copy,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  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));
hold on
axis manual
plot(xCoords, yCoords, 'b-'); % redraw in dataspace units

% Display the cropped image.
croppedImage = grayImage(y1:y2,x1:x2);
subplot(2, 2, 3);
imshow(croppedImage);
axis on;
title('Region that you defined', 'FontSize', fontSize);

% Paste it onto the original image
[rows2 columns2] = size(croppedImage)
promptMessage = sprintf('Click on the upper left point where you want to paste it,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
[x, y] = ginput(1)
% Determine the pasting boundaries.
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.
grayImage(r1:r2, c1:c2) = croppedImage(1:(r2-r1+1), 1:(c2-c1+1));
subplot(2, 2, 4);
imshow(grayImage);
axis on;
title('Region that you defined pasted onto original', 'FontSize', fontSize);

Answer 4

[Mohseena Ansar]

can you give matlab code for pasting different portions of an image into a plane image...?

[Image Analyst]

See my two attached copy and paste demos.