MATLAB: How to save ROI parameters from DrawFreehand and load it onto another image

analysisdraw freehandImage Processing Toolboxroi

I'm working on a programme that analyses the contents within an ROI (such as Mean Grey Intensity). The images i want to measure are not clear enough to draw an ROI, but I have an image that is the same size (160x160px) and I would like to draw the ROI on that image and then display that ROI on the other images. I have the images uploaded in "axes" in the app designer. Any help is appreciated.

Best Answer

Here is what I do:

% User draws curve on image here.
hFH = drawfreehand();
% Get the xy coordinates of where they drew.
xy = hFH.Position
% get rid of imfreehand remnant.
delete(hFH);
% Overlay what they drew onto the image.
hold on; % Keep image, and direction of y axis.
xCoordinates = xy(:, 1);
yCoordinates = xy(:, 2);
plot(xCoordinates, yCoordinates, 'r.', 'LineWidth', 2, 'MarkerSize', 12);
caption = sprintf('Original Grayscale Image.\nPoints may not lie on adjacent pixels, depends on your speed of drawing!');
title(caption, 'FontSize', fontSize);

See attached full demo. Once you have xCoordinates and yCoordinates, you can save them and apply them to other images, for example by using them to create a mask with poly2mask().

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MATLAB: Find intersection between matrix and draw line on a figure

You forgot to post your image. Assuming you can segment out your cell then you just get (x,y) or (column, row) of the spot you want to track/trace and call

plot(x,y, 'r*-', 'MarkerSize', 5, 'LineWidth', 2);

Adjust options as desired.

By the way, imfreehand does give you the x,y coordinates in terms of column, row that are actual for the original full size image, not the on-screen pixels. See attached demo which has code like this:

% User draws curve on image here.
hFH = imfreehand();
% Get the xy coordinates of where they drew.
xy = hFH.getPosition
% get rid of imfreehand remnant.
delete(hFH);
% Overlay what they drew onto the image.
hold on; % Keep image, and direction of y axis.
xCoordinates = xy(:, 1);
yCoordinates = xy(:, 2);
plot(xCoordinates, yCoordinates, 'ro', 'LineWidth', 2, 'MarkerSize', 10);

MATLAB: Hi,, i’m new in matlab.. i want to draw using the mouse with this code, but this code can only make one line,, i want to make it more..,

Hi,

The simplest way is initialising an axes object that imfreehand() function can draw on to, and put your function into an infinite loop, like this:

ax=axes();
while true
    hFH = imfreehand(ax); % Get the xy coordinates of where they drew. 
    xy = hFH.getPosition; % get rid of imfreehand remnant.
    delete(hFH); % Overlay what they drew onto the image.
    hold on; % Keep image, and direction of y axis.
    x = xy(:, 1);
    y = xy(:, 2);
    % X = [X x];
    % Y = [Y y];
    line(x, y, 'Color','k','LineWidth', 4);
end

Is this what you are looking for?

Best Answer

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MATLAB: Find intersection between matrix and draw line on a figure

MATLAB: Hi,, i’m new in matlab.. i want to draw using the mouse with this code, but this code can only make one line,, i want to make it more..,

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