to extract pixel value from difference of gaussian filter

% Computes a Difference oOf Gaussians filter. clc; % Clear the command window. close all; % Close all figures (except those of imtool.) clear; % Erase all existing variables. workspace; % Make sure the workspace panel is showing. format longg; format compact; fontSize = 20;

I=imread('1.jpg'); grayImage = rgb2gray(I); % Get the dimensions of the image. % numberOfColorBands should be = 1. [rows columns numberOfColorBands] = size(grayImage); % Display the original gray scale image. subplot(2, 2, 1); imshow(grayImage, []); title('Original Grayscale 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','graphs','numbertitle','off')

% Let's compute and display the histogram. [pixelCount grayLevels] = imhist(grayImage); subplot(2, 2, 2); bar(pixelCount); grid on; title('Histogram of Original Image', 'FontSize', fontSize); xlim([0 grayLevels(end)]); % Scale x axis manually.

gaussian1 = fspecial('Gaussian', 21, 15); gaussian2 = fspecial('Gaussian', 21, 20); dog = gaussian1 - gaussian2; dogFilterImage = conv2(double(grayImage), dog, 'same'); subplot(2, 2, 3); imshow(dogFilterImage, []); title('DOG Filtered Image', 'FontSize', fontSize); imtool(dogFilterImage);

% Let's compute and display the histogram. [pixelCount grayLevels] = hist(dogFilterImage(:)); subplot(2, 2, 4); bar(grayLevels, pixelCount); grid on; title('Histogram of DOG Filtered Image', 'FontSize', fontSize);

xlim([0 grayLevels(end)]); % Scale x axis manually. yRange = ylim; % Calculate the mean gray level meanGL = sum(pixelCount .* grayLevels) / sum(pixelCount); meanBinHeight = mean(pixelCount); line([meanGL meanGL], yRange); message = sprintf('The mean gray level is %6.2f', meanGL); text(meanGL+5, 0.8*yRange(2), message); message = sprintf('Done!\nThe mean gray level is %6.2f\nThe mean binheight = %.2f', ... meanGL, meanBinHeight); msgbox(message);

In the above program, i am getting negative values for some pixels(pixels of my interest) in difference of Gaussian filter for which i plotted imtool and positive values for remaining pixels. please help me in converting this image to binary image. i want negative valued pixels to be white(255) and remaining all pixels to black(0).

Answer 1

[Image Analyst]

Of course there will be negative values - a DoG filter is an edge detection filter.

If you want negative values to be white and zero and positive values to be black, you can do this

binaryImage = dogImage < 0;  % Logical image -- 0 and 1 (false and true)

If you want an uint8 integer image, multiply by 255

image255 = uint8(255 * binaryImage);

By the way, I attached my demo of a dog filter.