Matlab图像旋转错误排查及旋转裁剪图分窗口显示实现

Hey there! Let's work through your two MATLAB image processing questions step by step, using your code as a starting point.

Your current code uses imshow(uprightImage); hold on, which overwrites the same window with each new image. To get a separate window for every rotated pill, just add a figure() call before imshow—you can even name each window to keep track of which pill is which:

Replace the imshow(uprightImage); hold on line in your loop with:

figure('Name', sprintf('Upright Pill %d', k));
imshow(uprightImage);

This creates a new, named figure window for each object, so you can view all rotated crops side by side without overlapping.

The root cause here is a mismatch between how regionprops defines the Orientation angle and how imrotate interprets rotation angles:

• regionprops.Orientation: This value ranges from -90° to 0°, representing the angle between the x-axis (rightward) and the object's major axis. A 0° value means the pill is horizontal (pointing right), while -90° means it's vertical (pointing down).
• imrotate angle rule: Positive angles rotate images clockwise, negative angles rotate them counterclockwise.

Your original code uses uprightImage = imrotate(croppedImage, angle);, which applies the raw Orientation value directly. For example, a vertical pill with -90° orientation would get rotated counterclockwise 90°—resulting in a horizontal pill pointing left, not the upright right-facing result you want.

Fix 1: Correct the Rotation Direction #

Invert the angle to get the right rotation direction:

uprightImage = imrotate(croppedImage, -angle);

Fix 2: Handle Circular Pills #

For nearly circular pills (like some in pillsetc.png), Orientation is arbitrary (since circles have no distinct major axis), leading to random-looking rotations. You can skip rotating these by checking the Circularity property (values close to 1 mean the object is circular):

Update your regionprops call to include Circularity, then add a conditional check:

measurements = regionprops(thisObject, 'Orientation', 'BoundingBox', 'Circularity');

if measurements.Circularity < 0.9
    angle = measurements.Orientation;
    uprightImage = imrotate(croppedImage, -angle);
else
    uprightImage = croppedImage; % Keep circular pills as-is
end

Full Corrected Code #

Here's the complete code with both fixes applied:

clear; clc;
RGB = imread('pillsetc.png');
I = rgb2gray(RGB);
bw = imbinarize(I);
bw = bwareaopen(bw,30);
bw = imfill(bw,'holes');
imshow(bw)
[B,L] = bwboundaries(bw,'noholes');
imshow(bw)
[labeledImage, numBlobs] = bwlabel(bw);

for k = 1 : numBlobs
    thisObject = ismember(labeledImage, k);
    measurements = regionprops(thisObject, 'Orientation', 'BoundingBox', 'Circularity');
    croppedImage = imcrop(RGB, measurements.BoundingBox);
    
    % Apply rotation only to non-circular objects
    if measurements.Circularity < 0.9
        angle = measurements.Orientation;
        uprightImage = imrotate(croppedImage, -angle);
    else
        uprightImage = croppedImage;
    end
    
    % Show each result in a separate window
    figure('Name', sprintf('Upright Pill %d', k));
    imshow(uprightImage);
end

内容的提问来源于stack exchange，提问作者jane