Crop an image using coordinates

I am getting a grid for an image using vertical projection.

I want to crop the image part, within the 2 of the points as one cropping image.

Can someone advice me on this?

Thanks!

[darova]

What about find function? It can find index of point where y = 0

[Anonymous26]

@darova : Can you please explain this a bit?

[darova]

you have data (x,y) or only image (pixels)?

[Anonymous26]

I only have the image.

Answer 1

[Image Analyst]

I would use regionprops() to find the start and stop of each non-zero segment, then crop. Something like (untested)

props = regionprops(verticalProfile, 'PixelIdxList');
for k = 1 : length(props)
    row1 = props(k).PixelIdxList(1, 1)
    row2 = props(k).PixelIdxList(1, end)
    croppedImage = grayImage(row1:row2, :)
    imshow(croppedImage);
    drawnow;
end

[Image Analyst]

That looks like it should also work. It's just an alternative way. Is there something wrong with it?

[Anonymous26]

@Image Analyst

The image part between point 1 and 2 as one image, the image part between 2 and 3 as another image and so on.

[Image Analyst]

I don't understand. It looks like the cropping is being done by this line:

subImage = i(:, startingColumns(k):endingColumns(k)); 

Is it not? What do you want to crop out and save as a sub-image: BW or (the badly named) i?

[Anonymous26]

I will explain further.

Cropping is done by that part. That is correct.

In the grid there are 3 points. I want the cropping to be happend as;

Point 1 - 2 = A

Point 2 - 3 = B

[Image Analyst]

Post the image with the paper clip icon.

[Image Analyst]

But you are further saving out each blob in a vertical band, like, because you labeled it, you are getting two blobs in the rightmost band. Do you want two there or one? If one, get rid of the inner loop.

[Anonymous26]

I want only one there.

[Image Analyst]

Hopefully you tried what I told you about removing the inner loop. Did you? If not, why not?

Here is what you should have gotten:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 14;

% cd('F:\Matlab Research\Images\Codes');
% myFolder = 'F:\Matlab Research\Images\Codes';
myFolder = pwd;
pathname = pwd;
% [filename, pathname] = uigetfile('*.png','Select image to be read');
filename = 'image.png';

grayImage= imread(fullfile(pathname,filename));
if ndims(grayImage) > 1
	% Take blue channel
	grayImage = grayImage(:, :, 3);
end
grayImage=padarray(grayImage,[0 1]);
letterLocations = any(grayImage > 128, 1);
subplot(2, 2, 1);
imshow(grayImage);
subplot(2,2, 3:4);
plot(letterLocations, 'b-', 'LineWidth', 2);
title('Projection down vertically');
grid on;
% Find Rising and falling edges
d = diff(letterLocations);
startingColumns = find(d>0)
% disp (startingColumns)
endingColumns = find(d<0)
% disp (endingColumns)
% Extract each letter.
numLetters = length(startingColumns)
plotRows = ceil(sqrt(numLetters + 3))
subplot(plotRows, plotRows, 1);
imshow(grayImage);
impixelinfo;
title('Original Image', 'FontSize', fontSize);
subplot(plotRows, plotRows, 2:3);
plot(letterLocations, 'b-');
title('Projection down vertically');
grid on;

% Extract each letter.
for k = 1 : numLetters
	% Get sub image of just one character...
	subImage = grayImage(:, startingColumns(k):endingColumns(k));
	[L, numberOfBlobsInThisBand] = bwlabel(subImage);
	baseFileName = sprintf('c%d.png', k);
	% Prepend the folder to make the full file name.
	fullFileName = fullfile(myFolder, baseFileName);
	% Do the write to disk.
	% 		imwrite(bw, fullFileName);
	subplot(plotRows, plotRows, k + 3);
	imshow(subImage);
	caption = sprintf('Letter %d of %d', k, numLetters);
	title(caption);
end

[Anonymous26]

@Image Analyst

Thank you for your response.

When i am trying the code, i am getting the following error sir.

Index in position 3 exceeds array bounds (must not exceed 1).

Error in Untitled114 (line 17)

grayImage = grayImage(:, :, 3);

[Image Analyst]

It should only get to that line if it's an RGB image. What does this say?

ndims(grayImage)
whos grayImage
[rows, columns, numberOfColorChannels] = size(grayImage)

Don't use semicolons and look to see what it reports to the command window.

[Anonymous26]

@Image Analyst

Thank you so much for your support. I made some modifications in the code and made it work, according to my need.

Thanks a lot again!

Answer 2

[darova]

Here is an attempt

clc,clear

I = imread('Capture.jpeg');
I1 = im2bw(I);                  % convert to binary
I2 = bwareaopen(~I1,100);       % remove numbers (small areas)
[row,col] = find(I2);
I3 = I2*0;
h = 1;                          % crop thickness
ii = row(1)+h:row(end)-h;
jj = col(1)+h:col(end)-h;
I3(ii,jj) = I2(ii,jj);          % crop
I4 = bwareaopen(I3,200);        % remove small areas
[L,n] = bwlabel(I4);            % label image

for i = 1:4
    subplot(2,2,i)
    I5 = L == i;                % find part of a curve
    I6 = imdilate(I5,ones(5));  % highlight the part
    II = cat(3,~I6,I1,I1)*255;
    imshow(II)                  % show original image and part of a curve
end

im assuming the original image has no those circles

[Anonymous26]

@darova

My image is not the attached one. That is the gride i got for the original image.

After getting that gride only i am trying to crop the image using the y = 0 points.

[darova]

Do you like my idea?