MATLAB: Crop a image using ‘imfreehand’ and move the cropped region to the center of black background

centercropped roiImage Processing Toolboxmatlab 2007

I've cropped an ROI with imfreehand() and plotted the center of it using mean (position of cropped region). Then I've plotted the center of completely black image. For the resulting image to have the cropped image at center of black background, is it OK to map the marked centers of both images, or get positions for moving the region manually? I want to do this for multiple images, so is it possible to apply any formula or function? Also I've attached example images and sample output. Kindly help me in this.

I've tried also tried using circular shift, circshift(), for moving the cropped portion to the center of black background, but it is not working. Applying a circular shift made the ROI to move like half portion up an remaining down the center of black image. Why did it appear so?

Original Image:

ROI with centroid marked:

Center of black image:

Desired output image:

Thank you and have a Good Day.

Best Answer

It's not obvious, but you can use imwarp() instead of circshift. See this demo:

% Shifts / translates an image to the right by 500 pixels and down by 200 pixels.
% Area shifted in is black.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
grayImage = imread('concordorthophoto.png');
[rows, columns, numberOfColorChannels] = size(grayImage);
subplot(1, 2, 1);
imshow(grayImage);
axis on;
title('Original Image', 'fontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
deltaX = 500; % Shift x by 500 pixels.

deltaY = 200; % Shift y by 200 pixels.
D = zeros(rows, columns, 2);
D(:,:,1) = -deltaX; % Shift x by 500 pixels.
D(:,:,2) = -deltaY; % Shift x by 200 pixels.
warpedImage = imwarp(grayImage, D);
subplot(1, 2, 2);
imshow(warpedImage);
axis on;
title('Shifted Image', 'fontSize', fontSize);

So just mask the image in place (see attached demo script freehand_masking_demo.m), then do the shifting with imwarp().

Related Solutions

MATLAB: How to fill the region inside a contour

Alright, try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
%===============================================================================
% Read in good demo image.
folder = pwd;
baseFileName = 'contour.jpg';
% 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.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, '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
rgbImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorChannels] = size(rgbImage);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = rgbImage(:, :, 2); % Take green channel.
else
  grayImage = rgbImage; % It's already grayscale.
end
% Display the image.




subplot(2, 3, 1);
imshow(grayImage, []);
axis on;
title('Gray Scale Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 
% Threshold the image
binaryImage = grayImage > 128;
% Display the image.
subplot(2, 3, 2);
imshow(binaryImage, []);
axis on;
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Get rid of huge white surround
binaryImage = imclearborder(binaryImage);
% Display the image.
subplot(2, 3, 3);
imshow(binaryImage, []);
axis on;
title('Border-cleared Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Close the image
se = strel('disk', 2, 0);
binaryImage = imclose(binaryImage, se);
% Display the image.
subplot(2, 3, 4);
imshow(binaryImage, []);
axis on;
title('Closed Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Fill holes
binaryImage = imfill(binaryImage, 'holes');
% Display the image.
subplot(2, 3, 5);
imshow(binaryImage, []);
axis on;
title('Final Image', 'FontSize', fontSize, 'Interpreter', 'None');

MATLAB: How to find the location of the pixels between adjacent regions.

As you can imagine, there will be some ambiguities in some places, like when three regions meet. However, that will be just at a few pixels. I'd recommend doing two for loops to find where every region overlaps every other region. Then dilate each region and AND them to find the overlap pixels. Run this demo:

clc;  % Clear command window.
clear;  % Delete all variables.
close all;  % Close all figure windows except those created by imtool.
imtool close all;  % Close all figure windows created by imtool.
workspace;  % Make sure the workspace panel is showing.
fontSize = 15;
% 1.
% Make a binary image containing two overlapping circular objects.
center1 = -10;
center2 = -center1;
dist = sqrt(2*(2*center1)^2);
radius = dist/2 * 1.4;
lims = [floor(center1-1.2*radius) ceil(center2+1.2*radius)];
[x,y] = meshgrid(lims(1):lims(2));
bw1 = sqrt((x-center1).^2 + (y-center1).^2) <= radius;
bw2 = sqrt((x-center2).^2 + (y-center2).^2) <= radius;
bw = bw1 | bw2;
figure;
% 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');
subplot(2, 2, 1);
imshow(bw,'InitialMagnification','fit');
title('bw', 'FontSize', fontSize);
%  2.
% Compute the distance transform of the complement of the binary image.
D = bwdist(~bw);
subplot(2, 2, 2);
imshow(D,[],'InitialMagnification','fit')
title('Distance transform of ~bw', 'FontSize', fontSize)
% 3.
% Complement the distance transform, and force pixels that don't belong to the objects to be at -Inf.
D = -D;
D(~bw) = -Inf;
% 4.
% Compute the watershed transform and display the resulting label matrix as an RGB images. 
L = watershed(D);
rgb = label2rgb(L,'jet',[.5 .5 .5]);
subplot(2, 2, 3);
imshow(rgb,'InitialMagnification','fit')
title('Watershed transform of D', 'FontSize', fontSize)
% Code above was from the watershed demo, with some changes by Image Analyst.
% Code below is from Image Analyst.
numberOfRegions = max(L(:));
figure;
% 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') 
for r1 = 1 : numberOfRegions
  % Get the region

  region1 = ismember(L, r1);
  % Dilate it.

  region1Dilated = imdilate(region1, true(3));
  for r2 = r1 + 1 : numberOfRegions
    % Get the region
    region2 = ismember(L, r2);
    % Dilate it.
    region2Dilated = imdilate(region2, true(3));
    % Find the intersection
    intersectionRegions = region1Dilated & region2Dilated;
    
    % Display everything.
    subplot(2, 3, 1);
    imshow(region1);
    title('Region1', 'FontSize', fontSize);
    subplot(2, 3, 4);
    imshow(region1Dilated);
    title('Region1 Dilated', 'FontSize', fontSize);
    subplot(2, 3, 2);
    imshow(region2);
    title('Region2', 'FontSize', fontSize);
    subplot(2, 3, 5);
    imshow(region2Dilated);
    title('Region2 Dilated', 'FontSize', fontSize);
    subplot(2, 3, 6);
    imshow(intersectionRegions);
    title('intersectionRegions', 'FontSize', fontSize);
  end
end

Best Answer

Related Solutions

MATLAB: How to fill the region inside a contour

MATLAB: How to find the location of the pixels between adjacent regions.

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