Poor Contrast Image?

I used a threshold technique to change the black backround of an RGB image to Gray with a but it didn't work properly. Since it changes the pixels which are black inside the image also to gray. The code used is:

 X=imread('f100.bmp);
  im2=x;
  greycol= intmax(class(X))/2;
  [rows,cols,panes] = size(X);
  blacks = find(~sum(X,3));
  im2( [blacks,blacks + rows*cols,blacks+2*rows*cols] ) = greycol;
   imshow(im2)

Can anybody help me in improving the code or any suggestions?

Answer 1

[Image Analyst]

Try this code:

clc;
clearvars;
close all;
workspace;
fontSize = 20;

% Read in color demo image.
folder = 'C:\Users\Sachin\Documents\Temporary';
baseFileName = 't56hll.jpg';
fullFileName = fullfile(folder, baseFileName);
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % 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.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
rgbImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows columns numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 2, 1);
imshow(rgbImage, []);
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);

% Binarize the red channel low enough to leave unwanted clutter.
binaryImage = redChannel > 30;
% Display the binary image.
subplot(2, 2, 2);
imshow(binaryImage, []);
title('Initial Binary Image', 'FontSize', fontSize);

% Measure areas
labeledImage = bwlabel(binaryImage);
blobMeasurements = regionprops(binaryImage, 'area');

% Now I'll demonstrate how to select certain blobs based using the ismember function.
allBlobAreas = [blobMeasurements.Area];
% Get a list of the blobs that meet our criteria and we need to keep. 
allowableAreaIndex = allBlobAreas == max(allBlobAreas); % Take the largest object only.
keeperIndex = find(allowableAreaIndex); 
% Extract only those blobs that meet our criteria, and 
% eliminate those blobs that don't meet our criteria. 
% Note how we use ismember() to do this.
keeperBlobsImage = ismember(labeledImage, keeperIndex); 

% Fill in holes
mask = imfill(keeperBlobsImage, 'holes');
% Display the binary image.
subplot(2, 2, 3);
imshow(mask, []);
title('Final Mask Image', 'FontSize', fontSize);

% Mask the image.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask,class(rgbImage)));
subplot(2,2,4);
imshow(maskedRgbImage);
title('Final Masked RGB Image', 'FontSize', fontSize);

[Sachin]

HI There, This works fantastic and I understand what you did to Initial Binary Image by filling up with holes. But the point was to get the gray background image as final result. I tried to manupulate your final mask but didn't get success, I tried following things as an extension of your code:

Grayimage=rgb2gray(rgbImage);

grayMaskedimage(~binaryImage)=150;

Mask2=zeros(480,480);

for i = 1:480

for j = 1:480

if grayMaskedimage(i,j) == 150

Mask2(i,j) = 1;

else

Mask2(i,j) = 0;

end

end

end

But this Mask2 doesn't seem alright.

[Image Analyst]

So just add this line after the imfill() line:

% Invert it to get the gray background

mask = ~mask;

Plus, you've go to get away from that "for loop way of thinking" - you're not utilizing one of the best and most powerful features of MATLAB!

Answer 2

[Image Analyst]

Using any kind of point process like intlut() or im2(im2==0) = greycol (there - there's your suggestions) will change all black pixels to gray no matter where they are. If you have a foreground and background and your foreground object has some "holes" in it, then you need to create a mask that has foreground and background where the foreground is solid - no holes. Very easy to do. Why don't you upload an image somewhere, such as tinypic.com?

[Sachin]

Please follow the link below:

Original Image:

http://i48.tinypic.com/t56hll.jpg

Threholdded Image

http://i48.tinypic.com/34jf329.jpg