I used the "imfreehand" to crop an irregular shape and save its positions into a variable. This position variable is a 85*2 double matrix (85 points, X and Y coordinates). Now, I want to use the same position to crop another image (different layer of the image, but the location of the objects is the same). The functions I can find all requires rectangle positions (X1,X2,Y1,Y2). In my situation, I have 82 different (X,Y) coordinates, how can I use the position information to crop a new image?
MATLAB: Crop an image using multiple coordinates
croppinggetpositionimcropimfreehandMATLAB
Related Solutions
Try this:
% Mask the image.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, 'like', rgbImage));where mask is your binary image.
See if my imfreehand demo helps you:
% Demo to have the user freehand draw an irregular shape over
% a gray scale image, have it extract only that part to a new image,
% and to calculate the mean intensity value of the image within that shape.
% By ImageAnalyst
% Change the current folder to the folder of this m-file.
if(~isdeployed) cd(fileparts(which(mfilename)));endclc; % 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 = 16;% Read in standard MATLAB gray scale demo image.
grayImage = imread('cameraman.tif');subplot(2, 3, 1);imshow(grayImage, []);title('Original Grayscale Image', 'FontSize', fontSize);set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.
message = sprintf('Left click and hold to begin drawing.\nSimply lift the mouse button to finish');uiwait(msgbox(message));hFH = imfreehand();% Create a binary image ("mask") from the ROI object.
binaryImage = hFH.createMask();% Display the freehand mask.
subplot(2, 3, 2);imshow(binaryImage);title('Binary mask of the region', 'FontSize', fontSize);% Calculate the area, in pixels, that they drew.
numberOfPixels1 = sum(binaryImage(:))% Another way to calculate it that takes fractional pixels into account.
numberOfPixels2 = bwarea(binaryImage)% Get coordinates of the boundary of the freehand drawn region.
structBoundaries = bwboundaries(binaryImage);xy=structBoundaries{1}; % Get n by 2 array of x,y coordinates.
x = xy(:, 2); % Columns.
y = xy(:, 1); % Rows.
subplot(2, 3, 1); % Plot over original image.
hold on; % Don't blow away the image.
plot(x, y, 'LineWidth', 2);% Burn line into image by setting it to 255 wherever the mask is true.
burnedImage = grayImage;burnedImage(binaryImage) = 255;% Display the image with the mask "burned in."
subplot(2, 3, 3);imshow(burnedImage);caption = sprintf('New image with\nmask burned into image');title(caption, 'FontSize', fontSize);% Mask the image and display it.
% Will keep only the part of the image that's inside the mask, zero outside mask.
blackMaskedImage = grayImage;blackMaskedImage(~binaryImage) = 0;subplot(2, 3, 4);imshow(blackMaskedImage);title('Masked Outside Region', 'FontSize', fontSize);% Calculate the mean
meanGL = mean(blackMaskedImage(binaryImage));% Report results.
message = sprintf('Mean value within drawn area = %.3f\nNumber of pixels = %d\nArea in pixels = %.2f', ...meanGL, numberOfPixels1, numberOfPixels2);msgbox(message);% Now do the same but blacken inside the region.
insideMasked = grayImage;insideMasked(binaryImage) = 0;subplot(2, 3, 5);imshow(insideMasked);title('Masked Inside Region', 'FontSize', fontSize);% Now crop the image.
topLine = min(x);bottomLine = max(x);leftColumn = min(y);rightColumn = max(y);width = bottomLine - topLine + 1;height = rightColumn - leftColumn + 1;croppedImage = imcrop(blackMaskedImage, [topLine, leftColumn, width, height]);% Display cropped image.
subplot(2, 3, 6);imshow(croppedImage);title('Cropped Image', 'FontSize', fontSize);
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