MATLAB: Find black images in a file

.jpgblack imageImage Processing Toolbox

Hello, So I have this file with jpg images (more than 5000 images), and some of them are completely black. I want to know how many black images I have in my file. I never worked with loading and doing loops with jpg images so I don't know how to generate the code. I was thinking on doing a loop where if the sum of the pixels would be zero (all pixels black), then it would be a black image, else a color image. The problem is that I don't know how to address the pixels in the image matrix.

Thanks in advance!

Best Answer

Yes, you can do that. First use one of the code samples in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Before the loop, put this:

count = 0;

In the middle of the loop, put this:

theSum = sum(sum(imageArray));
if theSum == 0
  count = count + 1;
  blackFiles{count} = fullFileName; % Or whatever
end

Related Solutions

MATLAB: Black and white image

Try this

[counts, grayLevels] = imhist(grayImage, 256);
if sum(counts(2:end-1)) > 0
  % It's not pure black and white
end
% Get map of non-0 and non-255 pixels
grayPixels = grayImage > 0 & grayImage < 255;
% Get pure black and white image
bw = grayImage; % Initialize

bw(grayPixels) = 0; % Zero out any gray pixels.
% Get gray pixels only
grayOnly = grayImage; % Initialize
grayOnly(~grayPixels) = 0; % Zero out any pure 0 or pure 255 pixels.

MATLAB: Recognize black dot

Well now that you posted an image, and I see you have black spots not only on the dice but also on the red background, I need to modify my answer to have you threshold on the blue or green channel:

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;
folder = 'C:\Documents and Settings\user\My Documents\Temporary stuff';
% Read in a color demo image.
baseFileName = 'IMG_0584.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, 'Position', get(0,'Screensize')); 
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
spots = blueChannel < 128;
subplot(2, 2, 2);
imshow(spots, []);
title('Thresholded Blue Channel', 'FontSize', fontSize);
spots = imclearborder(spots);
subplot(2, 2, 3);
imshow(spots, []);
title('Border Cleared', 'FontSize', fontSize);
% Fill holes
spots = imfill(spots, 'holes');
subplot(2, 2, 4);
imshow(spots, []);
title('Final Spots Image', 'FontSize', fontSize);
% Count them
[labeledImage numberOfSpots] = bwlabel(spots);
message = sprintf('Done!\nThe number of spots (total on both dice) is %d', numberOfSpots);
msgbox(message);

Best Answer

Related Solutions

MATLAB: Black and white image

MATLAB: Recognize black dot

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