qtrgbsplit.m

quadtree implementation in matlab

% % The method uses three thresholds for red,green and blue blocks.
% % For any R/G/B block if the maximum value of the block elements minus the
% % minimum value of the block elements is greater than its respective threshold
% % then the RGB image is splitted into 4 blocks. 

% % Thresholds are specified as a value between 0 and 1, even if I is of class uint8 or
% % uint16. If I is uint8, the threshold value you supply is multiplied by
% % 255 to determine the actual threshold to use; if I is uint16, the
% % threshold value you supply is multiplied by 65535

% % Input: image I (true color) image matrix of size M-by-N-by-3.
% % Output: if image is split the method returns 
% %         size and starting coordinate indices of each block. If the
% %         image is not divided then it return -1 value for each output argument

function [b1r,b1c,b2r,b2c,b3r,b3c,b4r,b4c,szr,szc]=qtrgbsplit(I,varargin)

% % Default Values 
thvec=[0 0 0];                %lossless encoding
defaultValues = {thvec};      %threshold vector
% % % Assign Values
nonemptyIdx = ~cellfun('isempty',varargin);
defaultValues(nonemptyIdx) = varargin(nonemptyIdx);
[thvec] = deal(defaultValues{:});
% % %------------------------------------------------------
% % Handling Threshold vector for various
if(length(thvec)==0)
    error('threshold vector must have atleast one value');
elseif(length(thvec)==1)
    ThR=thvec(1);
    ThG=ThR;
    ThB=ThG;
 elseif(length(thvec)==2)
    ThR=thvec(1);
    ThG=thvec(2);
    ThB=ThG;
 elseif(length(thvec)>=3)
    ThR=thvec(1);
    ThG=thvec(2);
    ThB=thvec(3);
end

if(ThR<0 || ThR>1 || ThG<0 || ThG>1 || ThB<0|| ThB>1)
    error('threshold value(s) must be between 0 and 1');
end

str=class(I);
if(strcmp(str,'uint8'))
    ThR=ThR*255;
    ThG=ThG*255;
    ThB=ThB*255;
elseif(strcmp(str,'uint16'))
    ThR=ThR*65535;
    ThG=ThG*65535;
    ThB=ThB*65535;
else
    error('Input Image must be of type uint8 or uint16');
end
% % %------------------------------------------------------
% % % ThR,ThG,ThB

[ir ic id]=size(I);
if(id~=3)
    error('Input Matrix (Image) must be of size M-by-N-by-3 (true color)');    
end

b1r=-1;
b1c=-1;
b2r=-1;
b2c=-1;
b3r=-1;
b3c=-1;
b4r=-1;
b4c=-1;
szr=-1;
szc=-1;

if(ir==1 && ic==1)  % block of size=1 are not split
    return
end

I=double(I); %convert to double for processing

if( max(max(I(:,:,1)))-min(min(I(:,:,1))) > ThR ||...
    max(max(I(:,:,2)))-min(min(I(:,:,2))) > ThG ||...
    max(max(I(:,:,3)))-min(min(I(:,:,3))) > ThB )

   [b1r,b1c,b2r,b2c,b3r,b3c,b4r,b4c,szr,szc]=splitinto4(ir,ic);
end

I=converttoclass(I,str); % back to original type

% % -------------------------------------------------------------------------
% % This program or any other program(s) supplied with it does not provide any
% % warranty direct or implied. This program is free to use/share for
% % non-commercial purpose only, for any other usage contact with author.
% % Kindly reference author.
% % Thanking you.
% % @ Copyright M Khan
% % Email: [e-mail]
% %        [e-mail] 
% % http://www.geocities.com/mak2000sw