How to extract non zero values from an image?

Question

i want to extract lines from a text document. I can accomplish this by summing its columns and produce a 1 dimensional vector (This will be the horizontal projection of the image). This is the image

img = imcomplement(rgb2gray(imread('french.jpg')));
lines = sum(img, 2);
plot(lines);

If I plot this I can see that the zero values show the blank spaces and the peaks depict the lines. Here is the plot

So looking at the plot (and the array) I can tell that the third line is from array index 129:184. So to extract it I did this

test = lines(129:184);

It does not seem to work as if I do imshow(test) or imshow(test, []) It gives the following result. Not exactly the third line.

What am I doing wrong here?

Answer 1

You want to display the 2D image rather than 1D line:

imshow(img(129:184,:)) 

gives you line 129 - 184.