How can I save an image with its plotted centroids?

Question

Nathan Costin 2016-7-5

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评论： Image Analyst 2016-7-6

I have found the center of some cells in an image and successfully plotted the centroids over these positions. However when I attempt to save the image only the original image is saved. Is there a way of saving the image with the centroids plotted? The code I am using is below and starts after I have converted the image 'I' to a binary image and done some processing to remove the noise:

baccenter = regionprops(imclean4, 'centroid');
centroids = cat(1, baccenter.Centroid);
measurements = regionprops(imclean4, 'BoundingBox', 'Area');
centroiddata = regionprops('table', imclean4, 'Centroid')
areadata = regionprops('table', imclean4, 'Area')
imshow(I)
hold on
plot(centroids(:,1),centroids(:,2), 'b*')
hold off
number_of_bacteria = numel(centroiddata)
locPath2 = '\\userfs\nac515\w2k\MATLAB\Tables and Pictures';
prompt2 = 'What would you like the image file to be called? ';
[~,locName] = fileparts(input(prompt2,'s'));
locFull2 = fullfile(locPath2,[locName,'.jpg']);
imwrite(I, locFull2)

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Answer 1

Walter Roberson 2016-7-5

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You can use getframe to get a copy of what was rendered to the screen, and then imwrite() it to a file.

If you have Computer Vision Toolbox then you can instead not plot at all, and instead use insertShape to insert markers into the image array, and then imwrite() the image array.

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Thorsten 2016-7-5

在 MATLAB Online 中打开

You can use the following little convenience function to get things done:

function figwrite(filename)
if nargin == 0 % write to default file
  filename = 'fig.png';
  if exist('fig.png', 'file')
    s = input(['Overwrite existing file ' filename '? Y/N >>'], 's');
    if ~strcmpi(s, 'Y')
      disp('No file written.')
      return
    end
  end
end
F = getframe(gcf);
if isempty(F.colormap)
  imwrite(F.cdata, filename);
else
  imwrite(F.cdata, F.colormap, filename);
end

Nathan Costin 2016-7-6

Thanks for your help, I was able to solve the issue using saveas :)

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Answer 2

Image Analyst 2016-7-5

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https://ww2.mathworks.cn/matlabcentral/answers/293749-how-can-i-save-an-image-with-its-plotted-centroids#answer_227726

Or you can use export_fig

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Image Analyst 2016-7-5

编辑：Image Analyst 2016-7-5

在 MATLAB Online 中打开

Warning: getframe does NOT maintain the size of your original image. It gives you the displayed size, which can vary depending on how much room on your screen your figure takes up. Use getimage() to get the actual image instead of basically a screen capture. However, getimage() does not capture any graphics your put into the overlay so you'd have to burn those into the image, for example with the insertShape function that Walter mentioned.

See code that demonstrates this:

grayImage = imread('moon.tif');
[rows, columns, numberOfColorChannels] = size(grayImage)
imshow(grayImage);
hold on;
plot(100, 200, 'r+', 'LineWidth', 4, 'MarkerSize', 30);
frameStructure = getframe;
displayedImage = getimage();
[rows, columns, numberOfColorChannels] = size(frameStructure.cdata)
[rows, columns, numberOfColorChannels] = size(displayedImage)
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
frameStructure = getframe;
displayedImage = getimage();
[rows, columns, numberOfColorChannels] = size(frameStructure.cdata)
[rows, columns, numberOfColorChannels] = size(displayedImage)

Nathan Costin 2016-7-6

thank you very much for your help! I was able to solve the issue using saveas!

Image Analyst 2016-7-6

OK, fine if you don't care about the size. Like getframe, you don't get the same size as the original image. See the note for saveas in the help "Starting in R2016a, the size of saved figures match the size of the figure on the screen by default." So it saves the whole figure, not just the axes control only, and the size is different. But if you're okay with that, then have at it.

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