Creating a histogram in 3D using LAB colorspace

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Lab Rat
Lab Rat 2012-9-23
评论： Image Analyst 2014-8-8
I'm trying to segment an image using kmeans, but I'm trying to find the number of clusters by creating a 3D histogram in the LAB colorspace. I'm looking for a histogram similar to http://blogs.mathworks.com/steve/2010/12/23/two-dimensional-histograms/ but in all the 3 dimensions. So I'd appreciate any help with this.

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回答（3 个）

Image Analyst
Image Analyst 2012-9-23
编辑：Image Analyst 2012-9-23
Try this: http://rsb.info.nih.gov/ij/plugins/color-inspector.html It can be downloaded and run from within MATLAB using code like this that I've put into a shortcut:
% Windows installation instructions:
% First, download and install ImageJ from here:
% http://rsb.info.nih.gov/ij/download.html
% Then download the 3D Color Inspector plug-in for ImageJ here:
% http://rsb.info.nih.gov/ij/plugins/color-inspector.html
% and save it here:
% C:/Program Files/ImageJ/plugins/Color
%
% Now we need to enable the plug-in to work with MATLAB.
% First open your classpath file:
% C:\Program Files\MATLAB\R2012b\toolbox\local\classpath.txt
% for editing. Then add the following lines as new lines to your classpath file:
% C:/Program Files/ImageJ/ij.jar
% C:/Program Files/ImageJ/plugins/Color/Color_Inspector_3D.jar
clc; % Clear the MATLAB command window.
% User must browse for the file they want to open.
% Set up a starting/initial folder that they will start browsing from.
startingFolder = pwd; % Change to something specific if you want.
if ~exist(startingFolder, 'dir')
startingFolder = pwd;
end
% Bring up the "Open File" dialog box.
[baseFileName, folder] = uigetfile({'*.jpg;*.tif;*.png;*.gif;*.bmp','Image Files (jpg,tif,png,bmp,gif)';...
'*.*','All Files (*.*)' },'Specify image file', startingFolder);
if baseFileName ~= 0
% If they didn't click Cancel, build the full filename:
fullFileName = fullfile(folder, baseFileName)
% Now pass that into the 3D Color Inspector plugin, and you're done.
color_inspector(fullFileName)
end
You might also be interested in the "color frequency image". Code for it is here:
http://www.mathworks.com/matlabcentral/fileexchange/28164-color-frequency-image
Lab Rat
Lab Rat 2012-9-23
Thanks! That looks to be an excellent tool. But this is kind of an assignment, so I'm trying to code it myself albeit with a bit of help. From the link that I've pasted above, the author mentions that it is possible to modify the code a bit to view the histogram in 3D, so I've made a few changes but with no result. Here is the code so far
if true
I=imread('pill2.jpg');
imshow(I);
cform= makecform('srgb2lab');
im=applycform(I,cform);
im = lab2double(im);
l = im(:,:,1);
a = im(:,:,2);
b = im(:,:,3);
N = 101;
bin_centers = linspace(-100, 100, N);
subscripts = 1:N;
ai = interp1(bin_centers, subscripts, a, 'linear', 'extrap');
bi = interp1(bin_centers, subscripts, b, 'linear', 'extrap');
li = interp1(bin_centers, subscripts, l, 'linear', 'extrap');
ai = round(ai);
bi = round(bi);
li = round(li);
ai = max(min(ai, N), 1);
bi = max(min(bi, N), 1);
li = max(min(li, N), 1);
H = accumarray([bi(:), ai(:), li(:)], 1, [N N N]);
imshow(H);
end
Image Analyst
Image Analyst 2012-9-24
编辑：Image Analyst 2012-9-24
Well then just follow the demo given by Mathworks for this: http://www.mathworks.com/products/demos/image/color_seg_k/ipexhistology.html
Or, why not just create the 3D scatter plot of the RGB color gamut. You can construct 2D histograms by projecting them along the 3 different axial dimensions. See this demo:
% Creates a 3D scatter plot of an RGB color gamut of a color image.
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.
format longg;
format compact;
fontSize = 20;
% Read in a standard MATLAB color demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'peppers.png';
% 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.
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);
% Construct the 3D color gamut.
gamut3D = zeros(256,256,256);
for column = 1: columns
for row = 1 : rows
rIndex = redChannel(row, column) + 1;
gIndex = greenChannel(row, column) + 1;
bIndex = blueChannel(row, column) + 1;
gamut3D(rIndex, gIndex, bIndex) = gamut3D(rIndex, gIndex, bIndex) + 1;
end
end
% Get a list of non-zero colors so we can put it into scatter3()
% so that we can visualize the colors that are present.
r = zeros(256, 1);
g = zeros(256, 1);
b = zeros(256, 1);
nonZeroPixel = 1;
for red = 1 : 256
for green = 1: 256
for blue = 1: 256
if (gamut3D(red, green, blue) > 1)
% Record the RGB position of the color.
r(nonZeroPixel) = red;
g(nonZeroPixel) = green;
b(nonZeroPixel) = blue;
nonZeroPixel = nonZeroPixel + 1;
end
end
end
end
figure;
scatter3(r, g, b, 3);
xlabel('R', 'FontSize', fontSize);
ylabel('G', 'FontSize', fontSize);
zlabel('B', 'FontSize', fontSize);
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Image Analyst
Image Analyst 2014-8-8
Yes, you can actually run that program from MATLAB since it's a jar file. Here's a shortcut I made to do it:
% Windows installation instructions:
% First, download and install ImageJ from here:
% http://rsb.info.nih.gov/ij/download.html
% Then download the 3D Color Inspector plug-in for ImageJ here:
% http://rsb.info.nih.gov/ij/plugins/color-inspector.html
% and save it here:
% C:/Program Files/ImageJ/plugins/Color
%
% Now we need to enable the plug-in to work with MATLAB.
% First open your classpath file:
% C:\Program Files\MATLAB\R2013b\toolbox\local\classpath.txt
% for editing. Then add the following lines as new lines to your classpath file:
% C:/Program Files/ImageJ/ij.jar
% C:/Program Files/ImageJ/plugins/Color/Color_Inspector_3D.jar
% Just put them as the first two lines, without any # symbols, right before this line:
% # DO NOT MODIFY THIS FILE.
%
% With Windows 7 you will need to save this to a different folder, like your Documents folder
% or some folder you have write privileges for, because Windows won't let you save
% anything under the Program Files folder. Then copy it over to the
% C:\Program Files\MATLAB\R2013b\toolbox\local folder and say Yes when it asks
% you if it's allowed to do the copy. Close down MATLAB if it's open, then start MATLAB.
% After starting MATLAB, type javaclasspath on the command line
% to verify that the folders have been recognized and added to the javaclasspath.
clc; % Clear the MATLAB command window.
% User must browse for the file they want to open.
% Set up a starting/initial folder that they will start browsing from.
startingFolder = pwd; % Change to something specific if you want.
if ~exist(startingFolder, 'dir')
startingFolder = pwd;
end
% Bring up the "Open File" dialog box.
[baseFileName, folder] = uigetfile({'*.jpg;*.tif;*.png;*.gif;*.bmp','Image Files (jpg,tif,png,bmp,gif)';...
'*.*','All Files (*.*)' },'Specify image file', startingFolder);
if baseFileName ~= 0
% If they didn't click Cancel, build the full filename:
fullFileName = fullfile(folder, baseFileName)
% Now pass that into the 3D Color Inspector plugin, and you're done.
color_inspector(fullFileName)
end

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