Mercurial > hg > octave-shane
changeset 16630:5d6243c2acbf
rgb2ind.m: Enable handling of ND images, and enable n,tol,map,dither as inputs.
* rgb2ind.m: Enable handling of ND images, and enable n,tol,map,dither as inputs.
author | Adam H Aitkenhead <adamhaitkenhead@gmail.com> |
---|---|
date | Sat, 04 May 2013 10:53:43 +0100 |
parents | a1f613e5066d |
children | c979e6db619b |
files | scripts/image/rgb2ind.m |
diffstat | 1 files changed, 126 insertions(+), 27 deletions(-) [+] |
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--- a/scripts/image/rgb2ind.m +++ b/scripts/image/rgb2ind.m @@ -1,5 +1,6 @@ ## Copyright (C) 1994-2012 John W. Eaton ## Copyright (C) 2012 Carnë Draug +## Copyright (C) 2013 Adam H Aitkenhead ## ## This file is part of Octave. ## @@ -19,50 +20,148 @@ ## -*- texinfo -*- ## @deftypefn {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{map}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{n}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{tol}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{map}, @var{dither_option}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{n}, @var{dither_option}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{rgb}, @var{tol}, @var{dither_option}) ## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{map}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{n}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{tol}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{map}, @var{dither_option}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{n}, @var{dither_option}) +## @deftypefnx {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{R}, @var{G}, @var{B}, @var{tol}, @var{dither_option}) ## Convert an image in red-green-blue (RGB) color space to an indexed image. +## +## The input image @var{rgb} must be an N-dimensional RGB image (MxNxO...x3 array) where M,N,O... are the +## image dimensions, and the final dimension contains the values in the red, green and blue +## channels. Alternatively, the red, green and blue color channels can be input as separate arrays @var{R}, @var{G} and @var{B}. +## +## @var{map} defines the colormap to be used. Alternatively, @var{n} or @var{tol} may be used to define +## the maximum number of colors to use in an automatically generated colormap. @var{n} is related to @var{tol} +## by: @var{n} = (floor (1/@var{tol}) + 1)^3; +## @var{tol} must be >0 and <=1. +## +## @var{dither_option} is a string which enables or disables dithering: 'dither' (default) or 'nodither'. +## ## @seealso{ind2rgb, rgb2hsv, rgb2ntsc} ## @end deftypefn -## FIXME: This function has a very different syntax than the Matlab -## one of the same name. -## Octave function does not support N, MAP, DITHER, or TOL arguments. - ## Author: Tony Richardson <arichard@stark.cc.oh.us> ## Created: July 1994 ## Adapted-By: jwe -function [x, map] = rgb2ind (R, G, B) +function [x, map] = rgb2ind (varargin) + + ## Gather the inputs + if (nargin < 1 || nargin > 6) + print_usage (); + else + + ## Test for dither_option, by checking if the final input is a string + if ischar (varargin{end}) + dither_option = varargin{end}; + dither_check = true; + else + dither_option = 'dither'; + dither_check = false; + endif + + ## Read the rgb input + if (nargin-dither_check==1 || nargin-dither_check==2) + + rgb = varargin{1}; + if (size (rgb)(end) != 3) + error ("rgb2ind: The input image must be an RGB image (MxNxO...x3 array)."); + elseif (min (rgb(:)) < 0 || max (rgb(:)) > 1) + error ("rgb2ind: The input image must contain values between 0 and 1."); + endif + if (nargin-dither_check==2) + option = varargin{2}; + else + dither_option = 'nodither'; + endif + + ## Read the R,G,B inputs + elseif (nargin-dither_check==3 || nargin-dither_check==4) + + R = varargin{1}; + G = varargin{2}; + B = varargin{3}; + if (! size_equal (R, G, B)) + error ("rgb2ind: R, G, and B must have the same size"); + endif + if (nargin-dither_check==4) + option = varargin{4}; + else + dither_option = 'nodither'; + endif + + rgb = reshape ([R(:), G(:), B(:)], [size(R), 3]); - if (nargin != 1 && nargin != 3) - print_usage (); + endif + endif + + ## Apply a limited colormap if required + if (exist ('option','var')) + + if (size (option,1)==1) + + if option>0 && option<=1 + ## option: tol + tol = option; + n = (floor (1/option) + 1)^3; + else + ## option: n + n = option; + endif + optionstr = sprintf ('-colors %d',n); + + else + + ## option: map + map = option; + if (isequal (map(:,1),map(:,2)) || isequal (map(:,1),map(:,3)) || isequal (map(:,2),map(:,3))) + error ('rgb2ind: The colormap cannot contain matching R,G, or B channels.') + endif + fnmap = tmpnam; + map = reshape (map, size (map, 1), 1, 3); + imwrite (map, fnmap, 'tiff'); + optionstr = sprintf ('-map %s', fnmap); + + endif + + ## Prepare the Graphicsmagick dithering option + if strcmp (dither_option, 'nodither') + ditherstr = '+dither'; + elseif strcmp (dither_option, 'dither') + ditherstr = '-dither'; + endif + + ## Perform the image processing using Graphicsmagick + fna = tmpnam; + fnb = tmpnam; + imwrite (rgb, fna, 'tiff'); + gmstr = sprintf ('gm convert %s %s %s %s', fna, ditherstr, optionstr, fnb); + system (gmstr); + rgb = imread (fnb); + endif - if (nargin == 1) - rgb = R; - if (ndims (rgb) != 3 || size (rgb, 3) != 3) - error ("rgb2ind: argument is not an RGB image"); - else - R = rgb(:,:,1); - G = rgb(:,:,2); - B = rgb(:,:,3); - endif - elseif (! size_equal (R, G, B)) - error ("rgb2ind: R, G, and B must have the same size"); - endif - - x = reshape (1:numel (R), size (R)); - - map = unique ([R(:) G(:) B(:)], "rows"); - [~, x] = ismember ([R(:) G(:) B(:)], map, "rows"); - x = reshape (x, size (R)); + ## Conversion of rgb image to x,map + sz = size (rgb); + pr = prod (sz(1:end-1)); + x = zeros (sz(1:end-1)); + [map,~,x(:)] = unique (reshape(rgb, [pr, 3]), "rows"); ## a colormap is of class double and values between 0 and 1 - switch (class (R)) + switch (class (rgb)) case {"single", "double", "logical"} ## do nothing, return the same case {"uint8", "uint16"} - map = double (map) / double (intmax (class (R))); + map = double (map) / double (intmax (class (rgb))); case "int16" map = (double (im) + 32768) / 65535; otherwise