How to compare two images from each other: Round 2

Question

Frank 2011-5-13

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/7366-how-to-compare-two-images-from-each-other-round-2

Hello again!

Slightly stuck on this issue. I need help on finding a way for MatLab to follow an object from one picture to the next, automatically. I've written a small script from help online that allows me to select the object and determine its coordinates, but is there a way that MatLab can see the object without me manually tracing it?

Thanks!,

-Frank

Images:

Code:

    I = imread('rice.png');
    %%imshow(I)
    background = imopen(I,strel('disk',15));
    figure, surf(double(background(1:8:end,1:8:end))),zlim([0 255]);
    set(gca,'ydir','reverse');
    %%Darkens image
    I2 = I - background;
    %figure, imshow(I2)
    %%Increases contrast
    I3 = imadjust(I2);
    %figure, imshow(I3);
    %%Turns image into binary colors (Black and White)
    level = graythresh(I3);
    bw = im2bw(I3,level);
    bw = bwareaopen(bw, 50);
    %%figure, imshow(bw)
    cc = bwconncomp(bw, 4);
    cc.NumObjects
    %%Select grain connected to background
    grain = false(size(bw));
    grain(cc.PixelIdxList{50}) = true;
    figure, imshow(grain);
    labeled = labelmatrix(cc);
    whos labeled
    %%Color Shift
    RGB_label = label2rgb(labeled, @autumn, 'c', 'shuffle');
    figure, imshow(RGB_label)
    graindata = regionprops(cc, 'basic');
    graindata(1).Area
    %%Grain area
    grain_areas = [graindata.Area];
    [max_area, idx] = max(grain_areas);
    grain = false(size(bw));
    grain(cc.PixelIdxList{idx}) = true;
    figure, imshow(grain)
    %%Select a portion to allocate coordinates of object
    [x, y, ~, xi, yi] = roipoly(grain);
    BW = roipoly(100, 200, xi, yi);
    %%Displays xi, yi coordinates 
    figure, imshow(BW)
    grain2 = imread('Rice3.gif');
    [x2,y2,Bw,xi2, yi2] = roipoly(grain2);

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Frank 2011-5-13

My goal for this is to track the object and calculate how much it has moved from picture to picture

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Answer 1

Sean de Wolski 2011-5-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/7366-how-to-compare-two-images-from-each-other-round-2#answer_10115

在 MATLAB Online 中打开

For this rice example, what do you know about that grain that makes it different that the rest?

Its size (+- a few pixels due to digitization)
The area of its boundingbox
Eccentricity

These are just three options of:

doc regionprops

that could be used.

Basically you would isolate the object you want in the first image.
Run the same binarization operation on the second image
do a connected components analysis in both, keeping the connected component of interest in the first one. (doc bwconncomp)
Get the measurements of all objects in the second image.
Whichever one is the most similar is your match.

Note: these are just a few of the things you could do. Looking at your above binary image, binarized, they seem feasible. If you want to compare in non-binary images then we might have to figure out something a little more complicated.

By the way, well written question - this is what allows you get a good answer

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Sean de Wolski 2011-5-13

If the grain is the only object in the image (like above) then yes. If not it'll calculate the boundingbox for every object in CC. From this you'd have to figure out which one was the one you want.

Frank 2011-5-13