Rotate individual labelled/segmented characters about its centroid

Hi ,

How do I rotate the individual characters anti-clockwise 90 degrees about their own centroid?

I have obtained their centroids and other stuff:

Character # Mean Intensity Centroid(X) Centroid(Y) Area

# 1 54.8 16.7 57.6 109.0

# 2 62.8 33.5 57.6 136.0

# 3 79.5 51.5 57.3 106.0

# 4 66.1 59.9 28.1 145.0

# 5 62.4 68.1 56.7 100.0

# 6 65.6 77.2 29.0 100.0

# 7 55.4 85.6 55.2 56.0

# 8 55.5 94.9 26.0 50.0

# 9 67.3 100.2 56.9 118.0

#10 76.5 118.1 27.0 117.0

#11 65.7 116.6 56.4 118.0

#12 71.1 132.8 25.8 139.0

#13 59.9 130.7 53.2 102.0

#14 81.9 150.1 55.5 115.0

Things I have tried:

1.) tried cropping and rotate but could not crop individual characters and rotate

2.) Tried using BW2 = bwareafilt(BW,range) and rotate but the character rotate about the image centroid instead

3.) Wanted to tried bounded box but do not know how to write those codes

My codes

clear all;
I=imread('charact2.jpg');
J=imrotate(I,-180);
%Upright image
subplot(3, 3, 1);
imshow(J);
% Convert to binary image
J = im2bw(J,0.34);
%Remove symbol (row,column), convert to 1
J(6:42,7:41)=0;
subplot(3, 3, 2);
imshow(J)
% Identify each character by seeing which pixels are connected to each other.
labeledImage = bwlabel(J,8);    
coloredLabels = label2rgb (labeledImage, 'hsv', 'k', 'shuffle'); 
subplot(3, 3, 3);
imshow(coloredLabels)
% Get all the char properties. 
Measurements = regionprops(labeledImage,J,'all');
numberOfchar = size(Measurements, 1);
%get the centroids of ALL the char
fprintf(1,'Character #    Mean Intensity  Centroid(X) Centroid(Y)  Area\n')
for k = 1 : numberOfchar
xCenter = Measurements(k).Centroid(1);
yCenter = Measurements(k).Centroid(2);
Pixels = Measurements(k).PixelIdxList;
Intensity = mean(I(Pixels));
CharArea = Measurements(k).Area;
charOrientation = Measurements(k).Orientation;
fprintf(1,'#%2d %18.1f %13.1f %12.1f %12.1f\n', k,Intensity, xCenter, yCenter, CharArea);
end

Answer 1

[Madhav Thakker]

Hi Ronald,

I understand that you want to rotate the letters 90 degrees anticlockwise. You are correct about extracting bounding boxes. You can extract bounding boxes, rotate them, and paste them on a new image.

I am attaching a snippet that can help you.

another = zeros(size(J));
for k =1:numberOfchar
    croppedImage = imcrop(J, Measurements(k).BoundingBox);
    angle = 90;
    rotated = imrotate(croppedImage, angle);
    center_x = Measurements(k).Centroid(1);
    center_y = Measurements(k).Centroid(2);
    [rows, cols] = size(croppedImage);
    prev_x = round(center_y - cols/2);
    prev_y = round(center_x - rows/2);
    another(prev_x:prev_x+cols-1,prev_y:prev_y+rows-1) = rotated;
end
imshow(another)

Hope this helps.

[Ronald Lim]

Thank you for the answer!, it will be perfect if I can see the overlapping characters as well.

[Matt J]

Then you should Accept-click the answer. It appears to have resolved your question.

[Ronald Lim]

Upon trying the codes, I encountered 2 problems

1.) Some of the characters edges were clipped away. It did not show the full characters after being rotated.

2.) It did not work for other angles such as 35 degrees clockwise etc.

Which my original question is to rotate labelled/segmented characters.

[Image Analyst]

1. There is a 'loose' option to imrotate to enlarge the canvass so that the corners don't get clipped off.
2. No idea why it would not work for 35 degrees. Please upload the whole m-file and the image where that failed.

[Ronald Lim]

Attached was the image that was clipped off

[Image Analyst]

You forgot to attach your m-file. Also since some characters are taller than wide, if you rotate them in place, the characters would be overlapped. Why do you want to do that? Why not just crop each character out to its own subimage to deal with it?