rgbImage2ColorMap

Below is a demonstration of the features of the rgbImage2ColorMap function

Contents

Syntax

[C]=rgbImage2ColorMap(A,optStruct);

Description

The rgbImage2ColorMap creates a colormap based on an input RGB (red green blue) color image. Colormap colors are based on the intensities occuring in the image. Therefore monotonic color images probably yeild the best results.

Examples

clear; close all; clc;

Plot settings

fontSize=10;

Example: harvest colormap from image data

Import example images

%Set main folder
defaultFolder = fileparts(fileparts(mfilename('fullpath')));
pathName=fullfile(defaultFolder,'data','PICT');

% Load example images
loadName=fullfile(pathName,'leaf1.jpg'); %Load name
X_leaf=importdata(loadName); %Import image
X_leaf_intensity=mean(double(X_leaf),3);

loadName=fullfile(pathName,'fire.jpg'); %Load name
X_fire=importdata(loadName); %Import image
X_fire=X_fire(1:3:end,1:3:end,:); %Reduce resolution
X_fire_intensity=mean(double(X_fire),3);

Build colormaps from imported images

optStruct.n=250; %Number entries in the colormap
optStruct.numBins=25; %Number of bins to sample the colors (colors are averages across bins)
optStruct.normFactor=255; %Normalisation factor, e.g. max(X(:))

%Leaf colormap
[C_leaf]=rgbImage2ColorMap(X_leaf,optStruct);

%Fire colormap
[C_fire]=rgbImage2ColorMap(X_fire,optStruct);

Create example patch data to color surfaces

[X,Y,Z]=peaks(50);

Show colormap create results

cFigure;

%Show images
subplot(2,3,1);  imagesc(X_leaf);  axis equal; axis tight; axis off; hold on;
title('RGB leaf image');
hs=subplot(2,3,2); imagesc(X_leaf_intensity); axis equal; axis tight; axis off; hold on;
title('Colormapped image');
colormap(hs,C_leaf); colorbar; caxis([0 255]);

subplot(2,3,4);  imagesc(X_fire);  axis equal; axis tight; axis off; hold on;
title('RGB fire image');
hs=subplot(2,3,5); imagesc(X_fire_intensity); axis equal; axis tight; axis off; hold on;
title('Colormapped image');
colormap(hs,C_fire); colorbar; caxis([0 255]);

%Show surface data
hs=subplot(2,3,3);
h=surf(X,Y,Z); axis tight; axis off; hold on;
set(h,'EdgeColor','none'); shading interp;
camlight('headlight'); lighting phong;
title('Surface with leaf colormap');
colormap(hs,C_leaf); colorbar;

hs=subplot(2,3,6);
h=surf(X,Y,Z); axis tight; axis off; hold on;
set(h,'EdgeColor','none'); shading interp;
camlight('headlight'); lighting phong;
title('Surface with fire colormap');
colormap(hs,C_fire); colorbar;

Example: adjust harvested colormap

Use fact that flipped fire colormap looks like ice colormap and combine

C_fireIce=[rot90(C_fire,2); C_fire(2:end,:)];

hs=cFigure;
h=surf(X,Y,Z); axis equal; axis tight; axis off; hold on; view(2);
set(h,'EdgeColor','none'); shading interp;
title('Surface with fireIce colormap');
colormap(hs,C_fireIce); colorbar; caxis([-max(abs(Z(:))) max(abs(Z(:)))]);

GIBBON www.gibboncode.org

Kevin Mattheus Moerman, [email protected]