imshow() for multiple selected objects

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Veena Chatti 2020-10-6

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https://ww2.mathworks.cn/matlabcentral/answers/606241-imshow-for-multiple-selected-objects

评论： Ameer Hamza 2020-10-7

采纳的回答： Ameer Hamza

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Hi,

I have an image with ~200-250 labeled objects. How can I use imshow() to display multiple selected objects?

When I try this:

imshow(LL == 200)

It works to show the object labeled 200. Say I want to see 200 and 201. I tried:

imshow(LL == 200)
hold on
imshow(LL == 201)

This erases 200 and shows just 201.

Thanks for your suggestions and tips!

采纳的回答

Ameer Hamza 2020-10-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/606241-imshow-for-multiple-selected-objects#answer_506446

image(): https://www.mathworks.com/help/matlab/ref/image.html is better suited for this case. Or even pcolor(): https://www.mathworks.com/help/matlab/ref/pcolor.html.

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Veena Chatti 2020-10-6

Thank you, Ameer Hamza! This works like a charm to give it the same colormap.

Can you explain a little about the logic behind 'CDataMapping'? I took a look at the documentation. It says:

"Color data mapping method, specified as 'direct' or 'scaled'. Use this property to control the mapping of color data values in CData into the colormap. CData must be a vector or a matrix defining indexed colors. This property has no effect if CData is a 3-D array defining true colors.

'direct' — Interpret the values as indices into the current colormap. Values with a decimal portion are fixed to the nearest lower integer.

If the values are of type double or single, then values of 1 or less map to the first color in the colormap. Values equal to or greater than the length of the colormap map to the last color in the colormap."

So if I understand this correctly, it assigns them the same map, but since the objects might move between frames, the object indices/labels change. If I can get the object labels to stay the same, in the same order, will it give each label the same color?

Veena Chatti 2020-10-7

Thank you! I think I am beginning to follow the logic of how image() works. The trick is to find a way to get it to retain the labels while tracking the objects now.

I really appreciate all your help. Thanks again!