"cleaning" a horizontal line removal code for object detection.
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I have a code that removes horizontal lines in an image but the problem is that it removes some of the lines that are needed for object detection. Any ide on how to make my output "cleaner"?
here is my code:
A=imread('sheetmusic.jpg');
B=rgb2gray(A);
C=double(B);
for i=1:size(C,1)-2
for j=1:size(C,2)-2
%Sobel mask for x-direction:
Gx=( ( 2*C(i+2,j+1)+C(i+2,j)+C(i+2,j+2) ) - ( 2*C(i,j+1)+C(i,j)+C(i,j+2) ) );
%Sobel mask for y-direction:
%Gy=((2*C(i+1,j+2)+C(i,j+2)+C(i+2,j+2))-(2*C(i+1,j)+C(i,j)+C(i+2,j)));
%The gradient of the image
if(Gx~=0)
B(i,j)=abs(Gx);
end
end
end
figure,imshow(B); title('Sobel gradient');
and here is my input image:
and here is my output:
采纳的回答
Brian Hart
2018-12-22
Hi Janrex,
For a nice clean image like this, there's a very simple solution. Just compute a row sum; rows with staff lines have a lower sum:
tmp=sum(C,2);
figure;plot(tmp)
Now set those rows to white:
ind=find(tmp<1E5)
C(ind,:)=255;
figure;imagesc(C);axis image;
(The downsampled image above doesn't look great; looks better for real)
If the white lines through the notes cause issues, you could do some morphology to close them (dilate then erode).
5 个评论
Image Analyst
2018-12-22
To expand on the white line removal process some more: You'd do an opening (erosion then dilation) with imopen() using a 3x1 vertical filter [1;1;1], or taller if the lines were more than one row tall.
openedImage = imopen(C, [1;1;1]);
This will expand the black vertically. But it will do it everywhere, even where we didn't want it to happen. So we need to use it only where there was a white line.
So then you'd make a mask using
[rows, columns] = size(openedImage);
mask = repmat(tmp<1E5, 1, columns)
Then you'd replace the filtered image with the opened image but only within the mask area.
C(mask) = openedImage(mask);
Note: this was just off the top of my head - I did not test it.
Brian Hart
2018-12-22
Good catch; since it's a white line, it'd be the opposite operation.
Janrex Pensader
2018-12-28
Janrex Pensader
2019-1-15
Image Analyst
2019-1-15
Correct. You'd have to adjust it for each size image.
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Image Analyst
2018-12-22
0 个投票
Ditch that simplistic algorithm and go for one of the more robust algorithms published here: Algorithms on Musical Notation. I'm sure you'll find something much better.
2 个评论
Janrex Pensader
2018-12-28
Image Analyst
2018-12-28
OK. Good for them. I'm sure they will learn a lot doing that. Not sure if any of the published papers I gave the link to do it that way since CNN's been around only for about 6 years or so. You might get a publication out of it if it's not been done before. Maybe you could at least upload it to the File Exchange.
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