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From: ImageAnalyst on 1 May 2010 16:25
On May 1, 2:48 pm, Bhuvan <kushalbhu...(a)yahoo.co.in> wrote:
> ??? Undefined function or method 'sqrt' for input arguments of type 'uint8'.
>
> Error in ==> Untitled7 at 16
> deltaE = sqrt(deltaLImage.^2 + deltaAImage.^2 + deltaBImage.^2);
>
> steve Y is this???

-------------------------------------------------------------------------------------------
I'm not Steve but I'll answer. You need to cast them to double like
in 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.

% Change the current folder to the folder of this m-file.
% (The line of code below is from Brett Shoelson of The Mathworks.)
if(~isdeployed)
cd(fileparts(which(mfilename)));
end

% Read in standard MATLAB color demo image.
rgbImage1 = imread('peppers.png');
subplot(3, 4, 1);
imshow(rgbImage1, []);
title('Original Color Image');
set(gcf, 'Position', get(0,'Screensize')); % Enlarge figure to full
screen.

% Generate a second image from the first one.
rgbImage2 = imnoise(rgbImage1, 'gaussian', 0, 0.02) * 0.95;
subplot(3, 4, 5);
imshow(rgbImage2, []);
title('Other Color Image');

% Get the rgb to lab transform and convert both images.
cform = makecform('srgb2lab');
lab1 = applycform(rgbImage1,cform);
lab2 = applycform(rgbImage2,cform);

% Extract the component images like this:
LImage1 = double(lab1(:,:,1));
AImage1 = double(lab1(:,:,2));
BImage1 = double(lab1(:,:,3));
LImage2 = double(lab2(:,:,1));
AImage2 = double(lab2(:,:,2));
BImage2 = double(lab2(:,:,3));

% Display all the lab images.
subplot(3, 4, 2);
imshow(LImage1, []);
title('L1 Image');
subplot(3, 4, 3);
imshow(AImage1, []);
title('A1 Image');
subplot(3, 4, 4);
imshow(BImage1, []);
title('B1 Image');
subplot(3, 4, 6);
imshow(LImage2, []);
title('L2 Image');
subplot(3, 4, 7);
imshow(AImage2, []);
title('A2 Image');
subplot(3, 4, 8);
imshow(BImage2, []);
title('B2 Image');

deltaLImage = LImage1 - LImage2;
deltaAImage = AImage1 - AImage2;
deltaBImage = BImage1 - BImage2;

subplot(3, 4, 10);
imshow(deltaLImage, []);
title('Delta L Image');
subplot(3, 4, 11);
imshow(deltaAImage, []);
title('Delta A Image');
subplot(3, 4, 12);
imshow(deltaBImage, []);
title('Delta B Image');

% Get the Delta E image:
deltaEImage = sqrt(deltaLImage.^2 + deltaAImage.^2 + deltaBImage.^2);
meanDeltaE = mean(deltaEImage(:));
subplot(3, 4, 9);
imshow(deltaEImage, []);
title('Delta E Image');
message = sprintf('Done!\nThe mean Delta E (color difference) = %.2f',
meanDeltaE);
msgbox(message);
%---------------------- end of code----------------------------------

However I don't think those are actual CIELAB values so treat them as
relative. A and B values generally go between about -20 and +20, not
0-255 like the transform is giving.
-ImageAnalyst (not Steve - a different person)
From: Walter Roberson on 1 May 2010 22:09
Bhuvan wrote:
> ??? Undefined function or method 'sqrt' for input arguments of type 'uint8'.
>
> Error in ==> Untitled7 at 16
> deltaE = sqrt(deltaLImage.^2 + deltaAImage.^2 + deltaBImage.^2);
>
>
> steve Y is this???

Because it didn't seem worthwhile to go through the complete testing
phase for a function that only has 16 possible outputs, and which would
surely get badly misused if it existed.

You go an error message and were thus alerted to the problem that you
are trying to take integer square roots. If Mathworks had provided the
code, then you would have been completely baffled as to why the program
ran but your outputs were almost all 15. Remember, when you do
arithmetic using uint8, values "saturate" at the maximum uint8, 255, so
if any of your input values had been 16 or greater, the square of that
input would have saturated at 255; adding more things to that would have
left you with 255, and the integer square root would then have been 15
(15*15 is the the greatest square number less than or equal to 255.)
Thus, by NOT providing the code, Mathworks made your program easier to
debug.

If you REALLY want the uint8 square root code, we could probably come up
with something pretty efficient and fairly compact... and mostly useless.
From: Bhuvan on 4 May 2010 06:23
hey thanks a lot.....it works perfectly...
i'm also doing sketch based search...what i have done is to rangefilt the image so that the edges get prominent then take std value of the image...it works when when ur sketch is of same size as that of the picture...do have any better ideas how sketch based search can be made...in this user searches the images based on the sketch he draws....
From: Bhuvan on 4 May 2010 06:30
yea thanks....i'm trying to do sketch based search

i got this code
for freehand draw



function [lineobj,xs,ys] = freehanddraw(varargin)
% [LINEOBJ,XS,YS] = FREEHANDDRAW(ax_handle,line_options)
%
% Draw a smooth freehand line object on the current axis (default),
% or on the axis specified by handle in the first input argument.
% Left-click to begin drawing, right-click to terminate, or double-click
% to close contour and terminate.
%
%
% INPUT ARGUMENTS: First: axis handle (optional)
% Additional: valid line property/value pairs
%
% OUTPUT ARGUMENTS: 1) Handle to line object
% 2) x-data
% 3) y-data
% (Note that output args 2 and 3 can also be extracted from the first output
% argument.)
%
% Ex: [myobj,xs,ys] = freehanddraw(gca,'color','r','linewidth',3);
% freehanddraw('linestyle','--');
%
% Written by Brett Shoelson, PhD
% shoelson(a)helix.nih.gov
% 3/29/05
% Modified:
% 10/05/05: Now allows double-click closing of contour

axdef = 0;
if nargin ~= 0 & ishandle(varargin{1})
try
axes(varargin{1});
axdef = 1;
catch
error('If the initial input argument is a handle, it must be to a valid axis.');
end
end


%Get current figure and axis parameters
oldvals = get(gcf);
oldhold = ishold(gca);

%hold on;

set(gcf,'Pointer','crosshair','doublebuffer','on');

%Get the initial point
[xs,ys,zs] = ginput(1);

%Create and store line object
if axdef
lineobj = line(xs,ys,'tag','tmpregsel',varargin{2:end});
else
lineobj = line(xs,ys,'tag','tmpregsel',varargin{:});
end
setappdata(gcf,'lineobj',lineobj);


%Modify wbmf of current figure to update lineobject on mouse motion
set(gcf,'windowbuttonmotionfcn',@wbmfcn);
%fdsd
disp('stop');
set(gcf,'windowbuttondownfcn',@wbdfcn);
%Wait for right-click or double-click
while ~strcmp(get(gcf,'SelectionType'),'alt') & ~strcmp(get(gcf,'SelectionType'),'open')
drawnow;
end

%Extract xyz data from line object for return in output variables
%(Also retrievable from first output argument)
if nargout > 1
xs = get(getappdata(gcf,'lineobj'),'xdata')';
end
if nargout > 2
ys = get(getappdata(gcf,'lineobj'),'ydata')';
end

%Clear temporary variables from base workspace
evalin('caller','clear tmpx tmpy tmpz done gca lineobj');

%Reset figure parameters
set(gcf,'Pointer',oldvals.Pointer,...
'windowbuttonmotionfcn',oldvals.WindowButtonMotionFcn,...
'windowbuttondownfcn',oldvals.WindowButtonDownFcn,...
'doublebuffer',oldvals.DoubleBuffer);
%Reset hold value of the axis
if ~oldhold, hold off; end

function wbmfcn(varargin)
lineobj = getappdata(gcf,'lineobj');
if strcmp(get(gcf,'selectiontype'),'normal');
tmpx = get(lineobj,'xdata');
tmpy = get(lineobj,'ydata');
a=get(gca,'currentpoint');
%set(a,'units',points);
% set(a,'xlim',[0,1],'ylim',[0,1]);

% if(a==1)
set(lineobj,'xdata',[tmpx,a(1,1)],'ydata',[tmpy,a(1,2)]);
%else
% a=1;
%end
drawnow;
else
setappdata(gcf,'lineobj',lineobj);
end

function wbdfcn(varargin)
lineobj = getappdata(gcf,'lineobj');
if strcmp(get(gcf,'selectiontype'),'open')
tmpx = get(lineobj,'xdata');
tmpy = get(lineobj,'ydata');
a=get(gca,'currentpoint');
set(a,'xlim',[0,1],'ylim',[0,1]);
set(lineobj,'xdata',[tmpx,tmpx(1)],'ydata',[tmpy,tmpy(1)]);
setappdata(gcf,'lineobj',lineobj);
drawnow;
end
return


but it doesn't work.... the first mouse click on the figure generates a random line...then it's fine why is it so?
From: ImageAnalyst on 4 May 2010 11:54
On May 4, 10:23 am, Bhuvan <kushalbhu...(a)yahoo.co.in> wrote:
> hey thanks a lot.....it works perfectly...
> i'm also doing sketch based search...what i have done is to rangefilt the image so that the edges get prominent then take std value of the image...it works when when ur sketch is of same size as that of the picture...do have any better ideas how sketch based search can be made...in this user searches the images based on the sketch he draws....

-------------------------------------------------------------
No, I've only heard about it but I've never worked in that field.
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