MATLAB Answers


removing the noise

Asked by kash
on 18 Apr 2012
Latest activity Commented on by Hetal Jariwala on 26 Aug 2016

I have uploaded an image ,

please tell how to remove the extra white regions other than text must be removed ,i need only text ,please help




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4 Answers

Answer by Image Analyst
on 20 Apr 2012
 Accepted answer

For what's it's worth, here is 10 minutes worth of a very simplistic attempt to isolate letters. It obviously misses some of the letters for the reasons I mentioned in my comments above. That could possibly be fixed to get some of the missing ones, at the expense of altering the shapes of the ones it got correctly on the first pass, or maybe you can avoid even that with an even more sophisticated algorithm.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;
% Read in demo image.
folder = 'C:\Users\Kash\Documents\Temporary';
baseFileName = 'jlGZw.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
	% File doesn't exist -- didn't find it there.  Check the search path for it.
	fullFileName = baseFileName; % No path this time.
	if ~exist(fullFileName, 'file')
		% Still didn't find it.  Alert user.
		errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage)
% Display the original gray scale image.
subplot(2, 3, 1);
imshow(grayImage, []);
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 
% Convert to gray scale image and threshold to get binary image.
binaryImage = rgb2gray(grayImage) > 100;
% Display the image.
subplot(2, 3, 2);
imshow(binaryImage, []);
title('Binary Image', 'FontSize', fontSize);
% Invert it.
binaryImage2 = ~binaryImage;
% Display the image.
subplot(2, 3, 3);
imshow(binaryImage2, []);
title('Inverted Binary Image', 'FontSize', fontSize);
% Border kill.
binaryImage3 = imclearborder(binaryImage2);
% Get rid of blobs smaller than 15.
binaryImage3 = bwareaopen(binaryImage3, 15);
% Display the image.
subplot(2, 3, 4);
imshow(binaryImage3, []);
title('Binary Image', 'FontSize', fontSize);
% Crop to bounding box.
verticalProfile = any(binaryImage3, 2);
horizontalProfile = any(binaryImage3, 1);
x1 = find(horizontalProfile, 1, 'first');
x2 = find(horizontalProfile, 1, 'last');
y1 = find(verticalProfile, 1, 'first');
y2 = find(verticalProfile, 1, 'last');
binaryImage4 = imcrop(binaryImage3, [x1, y1, x2-x1+1, y2-y1+1]);
% Display the image.
subplot(2, 3, 5);
imshow(binaryImage4, []);
title('Binary Image', 'FontSize', fontSize);
% Label each blob with 8-connectivity, so we can make measurements of it
[labeledImage numberOfBlobs] = bwlabel(binaryImage4, 8);
% Apply a variety of pseudo-colors to the regions.
coloredLabelsImage = label2rgb (labeledImage, 'hsv', 'k', 'shuffle'); 
% Display the pseudo-colored image.
% Get all the blob properties.
blobMeasurements = regionprops(labeledImage, 'all');   
allAreas = [blobMeasurements.Area]
title('Labeled Letters', 'FontSize', fontSize);


on 20 Apr 2012

Thaks but some letters are missing and i did not get bounding box for each line for those text,i need two bounding boxes for each line(because it has two lines of text),please help

Yes, like I said. I can't continue/complete this for you - this is where you take over.

Thanks for the information. works like charm

Answer by Walter Roberson
on 18 Apr 2012

Everything in your images appears to be text. English in one patch, something Arabic-like in another patch, and some alphabet I do not recognize in a third patch.

Everything is text is some alphabet.


on 19 Apr 2012

ok walter plz tell how to draw bounding box for each word in that image

No, I do not know how to find word boundaries for the Arabic-like string, or for wasp-ish, or for Dalek.

on 20 Apr 2012

Walter i need for only hindi and english words

Answer by Geoff
on 19 Apr 2012

As Walter says, everything is text. Are you planning to use character recognition on this?

In your case, I'm going to assume you want to do the filtering only on the supplied images.

I would try something like this:

1. Detect blobs of connected pixels.
2. Go through your blob list and discard any that don't meet some required criteria (width, height, width/height ratio, number of pixels).
3. You are left with a list of all blobs that meet your 'goodness' criteria, and you construct an image using the pixels of those blobs.

An easy way to detect blobs is by the Union-Find algorithm:

There might be a nicer description somewhere else with pretty diagrams... Use Google.

You move through your image and do a Union on the current pixel with:

* the pixel immediately right (x+1, y)
* the pixel immediately down (x, y+1)
* the pixel immediately down and right (x+1,y+1)
* the pixel immediately down and left (x-1, y+1)

I haven't done this for years, and my brain doesn't feel like digging it up right now. But that's somewhere to start.


on 20 Apr 2012

GEof a bounding box for a word "Hydraulics Laboratory" and for a line which in in hindi,so i will get two bounding boxes for two lines

on 20 Apr 2012

Just to be clear here, are you intending to use this method on other images? Any useful method that you can apply to this image may well not work at all on other images. If you just want to do this image, is there a reason you need to "detect" the lines of text? Cos I know what I'd do... Click, click, click, click, click, click, click, click. Eight user-selected co-ordinates = two bounding polygons. Anyway, this thread seems to have gone beyond 'help with MatLab', and into 'please write my algorithm'-territory.

on 20 Apr 2012

Geof whats the solution for this

Answer by Image Analyst
on 19 Apr 2012

Well I didn't see any white text whatsoever. Only some black text interior to some white surround. (You could make it white though with inverting, border-clearing, hole-filling, and some other tricks though.) So my output image would be all zero. I think this task, doing OCR on text with very strange fonts, graphics, noise and all kinds of other garbage in the image is beyond kash's abilities or even mine. There are whole OCR companies with dozens of people who have worked on this for decades and even their accuracy would be low for these kinds of images.


on 20 Apr 2012

Oh! I never saw that image. I concur... Do the hard stuff BEFORE filtering out all the useful data from your image.

on 20 Apr 2012

S walter you are correcr cut i dont need ocr,i only need bounding box for each line of text

One way to do it is in my code that has the comment "% Crop to bounding box."

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