MATLAB: Custom Colours of a Pie Chart Sections

pie chart

Hello!

I wonder if it is possible to create a pie chart in such a way so as to have 6 equally sized sections – each of which is coloured in a specific shade of green or red -depending on the percentage input – 100% being the brightest red or green and 10% being very pale green or red. Thanks! Dima

Best Answer

It was necessary to get rid of the "clc" to get it to work.

Note: the sectors go counter-clockwise in a "pie" chart.

% Program to apply red and green tinted colors to pie segments
% depending on the size of the pie segment.
function test1()
    fontSize = 24;
    X = [0 0.5 -0.2 0.3 0.8 -0.7];
    fig = figure;
    ax = axes('Parent', fig);
    numberOfSegments = length(X);
    rgbmatrix = [1+(X(:) < 0).*X(:), 1-(X(:) > 0).*X(:), 1-abs(X(:))];
    hPieComponentHandles = pie(ax, ones(1,numberOfSegments));
    title('Pie Chart with Custom Colors', 'Parent', ax, 'fontSize', fontSize);
    % Enlarge figure to full screen.
    set(fig, 'units', 'normalized', 'outerposition', [0 0 1 1]);
    set(fig, 'name', 'Demo by ImageAnalyst & Tanuki', 'numbertitle', 'off')
    % Assign custom colors.
    for k = 1 : numberOfSegments
      % Create a color for this sector of the pie
      pieColorMap = rgbmatrix(k,:);  % Color for this segment.
      % Apply the colors we just generated to the pie chart.
      set(hPieComponentHandles(k*2-1), 'FaceColor', pieColorMap);
      set(hPieComponentHandles(k*2), 'String', num2str(X(k)), 'FontSize', fontSize );
    end

Related Solutions

MATLAB: How to convert specific pixel value to pseudocolor

Is one of these what you are looking for? Walter's right about the ambiguity so I picked a couple of possibilities (grayscale changing the image and not using a colormap, and RGB thresholding each channel individually) and programmed up a demo for you. If neither case is what you want, then you must clarify. Don't worry about the length, just copy, paste, and run, then study the code later.

clc;  % Clear command window.
clear;  % Delete all variables.
close all;  % Close all figure windows except those created by imtool.
imtool close all;  % Close all figure windows created by imtool.
workspace;  % Make sure the workspace panel is showing.
fontSize = 16;
% Read in a standard MATLAB color demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'football.jpg';
% 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);
% Threshold each color channel to get pixels darker than 40.

redMask = redChannel < 40;
greenMask = greenChannel < 40;
blueMask = blueChannel < 40;
% Apply the mask

redChannel(redMask) = 255;
greenChannel(greenMask) = 0;
blueChannel(blueMask) = 0;
% Recombine into RGB image.

rgbImage = cat(3, redChannel, greenChannel, blueChannel);
% Display

subplot(2, 2, 2);
imshow(rgbImage, []);
title('Masked Color Image', 'FontSize', fontSize);
promptMessage = sprintf('Now we will do it for a gray scale image?');
titleBarCaption = 'Continue with gray scale example?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmp(button, 'Cancel')
  return;
end
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'cameraman.tif';
% 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);
    uiwait(warndlg(errorMessage));
    return;
  end
end
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, 2, 3);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Get red, green, and blue channels.
redChannel = grayImage;
greenChannel = grayImage;
blueChannel = grayImage;
% Threshold each color channel to get pixels darker than 40.
mask = grayImage < 40;
% Apply the mask
redChannel(mask) = 255;
greenChannel(mask) = 0;
blueChannel(mask) = 0;
% Recombine into RGB image.
rgbImage = cat(3, redChannel, greenChannel, blueChannel);
% Display
subplot(2, 2, 4);
imshow(rgbImage, []);
title('Masked Color Image', 'FontSize', fontSize);

MATLAB: I am not sure how i can get histogram both the fig which i looked in are the same.. Anybody help me in completing the code.

Why are you computing the histogram yourself??? You know, there is a function for that called imhist() in the Image Processing Toolbox. See this demo:

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 = 22;
% 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
% Read in the image from disk.
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);
% Get histograms for each color channel.
[pixelCountsR grayLevelsR] = imhist(redChannel, 256);
[pixelCountsG grayLevelsG] = imhist(greenChannel, 256);
[pixelCountsB grayLevelsB] = imhist(blueChannel, 256);
% Plot them
subplot(2, 2, 2);
bar(grayLevelsR, pixelCountsR, 'BarWidth', 1, 'FaceColor', 'r');
grid on;
title('Red Histogram', 'FontSize', fontSize);
subplot(2, 2, 3);
bar(grayLevelsG, pixelCountsG, 'BarWidth', 1, 'FaceColor', 'g');
grid on;
title('Green Histogram', 'FontSize', fontSize);
subplot(2, 2, 4);
bar(grayLevelsB, pixelCountsB, 'BarWidth', 1, 'FaceColor', 'b');
grid on;
title('Blue Histogram', 'FontSize', fontSize);

Regarding your code...What do you think this line will do:

for k=1:0:256

You have a step size of 0!!!! And in this line:

for k=0:256

what do you think will happen when k = 256 in this line:

final(i,j)=z(1,k+1)+1;

Normally you run from 0 to 255 (but not as indexes) or from 1 to 256, not from 0 to 256.

Best Answer

Related Solutions

MATLAB: How to convert specific pixel value to pseudocolor

MATLAB: I am not sure how i can get histogram both the fig which i looked in are the same.. Anybody help me in completing the code.

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