problem with output of imrotate function.

Question

fred bnm 2018-5-25

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https://ww2.mathworks.cn/matlabcentral/answers/402636-problem-with-output-of-imrotate-function

编辑： sparrow Jr 2018-5-26

Hi, after using imrotate function, why center of object is changing. this problem is appear by obtain center of object before and after rotation. please guide me how to rotate image without changing coordination of center's object. original image:

output after rotation:

    clc;clear;
    img = imread('ms0.jpg');
    degree = 45;
    img1 = imrotate(img,-degree,'crop');
    prob1 = regionprops(img,'centroid');
    prob2 = regionprops(img1,'centroid');
    img_center = prob1.Centroid;
    img1_center = prob2.Centroid;
    img_center = round(img_center);
    img1_center = round(img1_center);
    fprintf('center before  rotation is : ( %d , %d ) \n.',img_center(1),img_center(2));
    fprintf('center after rotation is : ( %d , %d ) \n.',img1_center(1),img1_center(2));

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Answer 1

Image Analyst 2018-5-25

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https://ww2.mathworks.cn/matlabcentral/answers/402636-problem-with-output-of-imrotate-function#answer_321997

imrotate() rotates about the center of the center of the image. Your blob is not at the center of the image so it will move. Perhaps you should crop your image if you want it to be at the center of an image.

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Image Analyst 2018-5-26

在 MATLAB Online 中打开

See my Image Segmentation Tutorial to learn how you can call regionprops() to crop out the bounding box of your blob https://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862&sort=downloads_desc

props = regionprops(binaryImage, 'BoundingBox');
croppedImage = imcrop(binaryImage, props.BoundingBox);
imrotate(croppedImage, angle);

sparrow Jr 2018-5-26

编辑：sparrow Jr 2018-5-26

Hello, Sir.. Thank you so much for your comment in my thread. I would like to ask you further questions about matlab. Would you mind if I send you an email? Iam so sorry for my comment here.

Best regard, Sparrow.

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