How can I show a big image to the user, and let him zoom on it to click on specified points?

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Elena Casiraghi 2018-8-18

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https://ww2.mathworks.cn/matlabcentral/answers/415357-how-can-i-show-a-big-image-to-the-user-and-let-him-zoom-on-it-to-click-on-specified-points

编辑： Elena Casiraghi 2018-8-20

Hello I'm showing images (with a huge size) to the user, and he must selct pixels from it. However, selection must be precise and I would allow him to zoom on the shown images to selct the pixels with precision. However, the "zoom on" instruction doesn't work for me. This my code:

fig=figure('Name', 'select Cell pixels', ... 'Position',[1 scrsz(4) scrsz(3) scrsz(4)]); hold on; imshow(IRGB); zoom on; [X,Y]=getpts(fig); close(fig);

Can you help me?? just a note: when I show the image (with imshow()) the user can zoom. After executing the getpts ... the zoom is automatically turned off.

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Answer 1

Image Analyst 2018-8-18

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https://ww2.mathworks.cn/matlabcentral/answers/415357-how-can-i-show-a-big-image-to-the-user-and-let-him-zoom-on-it-to-click-on-specified-points#answer_333256

zoom_image.m

See my attached zooming demo.

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Elena Casiraghi 2018-8-19

Unluckily the magnification factor can work but doesn't completely help. Let me try to explain again my problem. I want to show to the user (a biologist and/or pathologist) a color image (histological image with huge resolution); the user must click on specific points (pixels) to choose them. Note that I need precision in the choice; for this reason I need to let the user to zoom in and out when choosing both the area where to select the pixels, and the pixels themselves (the user might want to zoom in and out to better "understand" the (histological) image and select the correct pixels).

To show the image and allow pixel selection I use instructions like the following: fig= figure('Name', 'Click on pixels of interest'); imshow(IRGB); [X,Y]=getpts(fig)

Now what happens is: AFTER the instructions: fig= figure('Name', 'Click on pixels of interest'); imshow(IRGB);

the image is shown and, as you might note from the following picture, the zoom in/out options are set on

However, after the necessary instruction: [X,Y]=getpts(fig) that allows me to collect the coordinates of the user's clicks, the zoom in/out options are set to off (see the image below).... How can I avoid this???

Image Analyst 2018-8-19

Maybe try ginput() instead of getpts().

Elena Casiraghi 2018-8-20

编辑：Elena Casiraghi 2018-8-20

Thanks again for your quick answer, but I already tried and it behaves exactly as getpts. Precisely, when called, ginput() sets the zoom off. Basically, what I need, is the behaviour of the DataCursor that I find in the menu bar of the figure:

Indeed, afetr zooming in and/or out, with the dataCursor I can move in the image and see the position and rgb value of pixels. However, the observed pixels are not recorded. I believe the behaviour of the DataCursor is implemented in the figure class, but I can't find its implementation. How can I modify the dataCursor behaviour do that it returns the coordinates of the pixels observed by the user? Or ... how can I add a further selection tool to the figure menu bar? Do you have any clue?

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