I am getting an error while running regionprops. How?

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Ad 2017-4-19

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评论： Ad 2017-4-23

[L,N] = superpixels(I,50);% superpixels=44 
props = regionprops(L,'MeanIntensity','PixelValues','PixelList','PixelIdxList');

I am getting this error."REGIONPROPS needs I as an input to calculate 'MeanIntensity'".

Thankyou

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Image Analyst 2017-4-19

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You need to pass in the original image. You can't just pass in the labeled image. If you want the mean intensity of regions in an image, of course you need to pass in the image itself. The labeled image L merely tells where the regions are in the original image. You have to pass in the image itself as the second argument if you want to measure its intensities in those regions.

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Image Analyst 2017-4-19

在 MATLAB Online 中打开

Yes, you have to pass in each color channel separately, not a 3-D RGB or LAB or HSV image. Like

L_Image = labImage(:, :, 1); % Extract the L channel.
props = regionprops(L, L_Image,'MeanIntensity','.......

Note, you used:

[L,N] = superpixels(I.......

following the Mathworks example of using crummy variable names. So I think you got confused between that L and the L of LAB color space. Be careful. The badly named L returned from superpixels is actually a labeled image, not the L color space image. It would be better to use descriptive variable names like

[labeledImage, numberOfLabels] = superpixels(.....
labImage = rgb2lab(rgbImage);
L_Image = labImage(:, :, 1); % Extract the L channel only.
A_Image = labImage(:, :, 2); % Extract the A channel only.
B_Image = labImage(:, :, 3); % Extract the B channel only.
propsL = regionprops(labeledImage, L_Image,'MeanIntensity','.......
propsA = regionprops(labeledImage, A_Image,'MeanIntensity','.......
propsB = regionprops(labeledImage, B_Image,'MeanIntensity','.......

Now you can get the mean value of each superpixel in each of the L, A, and B color channels.

Image Analyst 2017-4-22

编辑：Image Analyst 2017-4-22

在 MATLAB Online 中打开

I don't even know what "How to convert superpixel properties to individual pixel properties?" means. And what is that matrix? Is that from pdist2() where you passed in the LAB values of all the superpixels, like

distances = pdist2(labValues, labValues);

If so, then the array contains the delta E (color difference) between every superpixel and every other superpixel. Not sure what you want to do after that because I totally don't understand your last sentence/question. You have the original value and know the locations (row, column) and color value of every individual pixel inside each superpixel, but I really don't know what you mean by "individual pixel properties" and how you'd get those from superpixels.

Superpixels are an aggregation of pixels into similar adjacent groupings. You always still have the original image so if you want something from the original image, just use it. You can't go backwards without the original image. It would be like saying I have the mean of the entire image, now tell me the gray level of all the individual pixels. You just can't do that.

Walter Roberson 2017-4-23

If the color distance between P1 and P2 is "low", and the color distance between P2 and P3 is "low", but the color distance between P1 and P3 is not "low", then how do you want to handle the situation?

Ad 2017-4-23

@walter Roberson sir,

Do you mean pixel or superpixel by P1? If P1 means pixel, that is why I want to convert superpixel properties to all pixels within that superpixel region.

Thank you so much for pointing that out.

How do know what are the superpixels connected to each other ?

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Walter Roberson 2017-4-19

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You are passing in a label matrix but asking for mean intensity. In order to do both at the same time you need to pass the intensity matrix as well. If I recall correctly you would pass it as the second argument.