can any one tell me how to convert an image of type 'unit8' to the image of type 'float'.basicaly i am following a book of 'Digial Image Processing Using Matlab' where they try to enhance a gray image .following is the code.thanks in advance

w=fspecial('laplacian',0);
f=imread('aa.jpg');
g1=imfilter(f,w,'replicate');
imshow(g1,[])
%as we get only a possitve image so he first try to convert the image type from 'unit8'to 'float'.so he write like this%
f2=tofloat(f);
%at here i am getting an error as [UNDEFINED FUNCTION OR METHOD 'tofloat' FOR INPUT ARGUMENTS OF TYPE 'unit8'].at this stage i could not understand what to do.%
%forther code is writen like this %
g2=imfilter(f2,w,'replicate');
imshow(g2,[])
%then he subtract the images like%
g=f2-g2;
imshow(g);

Answer 1

[Walter Roberson]

f2 = single(f);   %if you want the data type that is most commonly called "float"
f2 = double(f);   %if you want the "natural" floating point data type
f2 = im2double(f); %if you also want the uint8 values rescaled to 0-1 range

[jagannath mishra]

sir i am using the code "f2=single(f);" %where f is the input image and f2 is the converted image by single(f).%But i am getting an problem with it ,i.e,its writen on the command window as "Warning: Image is too big to fit on screen; displaying at 67% > In imuitools\private\initSize at 73 In imshow at 262 In page77 at 7 Warning: Image is too big to fit on screen;" please tell me what to do? thank you for your support

[Image Analyst]

Do nothing. It's just saying that it's zooming your picture so that it will fit onto your screen and you can see the whole image instead of just a small part of it. Don't worry about it. If you want, you can suppress the warning with this code:

% Turn off this warning "Warning: Image is too big to fit on screen; displaying at 33% "
% To set the warning state, you must first know the message identifier for the one warning you want to enable. 
% Query the last warning to acquire the identifier.  For example: 
% warnStruct = warning('query', 'last');
% messageID = warnStruct.identifier
% messageID =
%    MATLAB:Images:initSize:adjustingMag
warning('off', 'Images:initSize:adjustingMag');

Answer 2

[Steve Eddins]

tofloat is a function provided with the book you are reading. You can find it in Appendix C on page 806.

[jagannath mishra]

sorry sir i am using the 2nd edition of "DIGITAL IMAGE PROCESSING using MATLAB" by "R.C.GONZALEZ,R.E.WOODS,S.L.EDDINS" so i could not get it on the right place as you told. but according to you i try to find on Appendix C and get a code wcich is like

    function [f2,revertclass]=tofloat(f)
identity=@(X) X;
tosingle=@im2single;
table={'unit8',tosingle,@im2unit8
       'unit16',tosingle,@im2unit16
       'int16',tosingle,@im2int16
       'logical',tosingle,@logical
       'double',tosingle,identity
       'single',tosingle,identity};
   classindex=find(strcmp(class(f),table(:,1)));
   if isempty(classindex)
       error('unsupported input image class.');
   end
   out=table{classindex,2}(f);
   revertclass=table{classindex,3};
 "here%f is the input image by me%" but still i am getting some errors like
"%??? Error using ==> tofloat at 12
unsupported input image class.
Error in ==> page77 at 9
[f2,revertclass]=tofloat(f);
 %"

sir what to do now about this sir. thank you for your kind support.

[Walter Roberson]

'unit8' should be 'uint8' and likewise 'unit16' should be 'uint16'

[jagannath mishra]

sorry sir but can't understand

[Walter Roberson]

Change your code where you currently have

table={'unit8',tosingle,@im2unit8
       'unit16',tosingle,@im2unit16
       'int16',tosingle,@im2int16
       'logical',tosingle,@logical
       'double',tosingle,identity
       'single',tosingle,identity};

to become

table={'uint8',tosingle,@im2uint8
       'uint16',tosingle,@im2uint16
       'int16',tosingle,@im2int16
       'logical',tosingle,@logical
       'double',tosingle,identity
       'single',tosingle,identity};

[Image Analyst]

unit and uint are two different words. The middle two characters are swapped.

[玉山 邓]

dont like

Answer 3

[Kiranraddi morab]

hello sir i'm too getting the same error how to use [f,revertclass]=tofloat(f)... Undefined function 'tofloat' for input arguments of type 'uint8'. MATLAB has this function or what is the problem please help me out

[Image Analyst]

Did you see Steve's Answer about it being included with the book?

[Kiranraddi morab]

yeah thank you

[PRABAKARAN K]

dear the tofloat is an user defined fuction its not exist in MATLAB

the code for tofloat given in that book is bellow which s a user defined function

f u n c t i o n [ out , revert clas s ) = tofloat ( in )

%TOF LOAT Convert image t o floating point

% [ OUT , REVERTCLASS ] = TOFLOAT ( I N ) c o n v e r t s the input image IN t o

% float ing - point . If IN is a d o u b le o r single imag e , then OUT

% equals I N . O t h e rwise , OUT equals IM2SINGLE ( I N ) . REVERTCLASS is

% a f u n ct ion handle t h at can be used to c o n v e rt back to t he class

% of I N .

i d e n t i t y

t o s ingle

@ ( x ) x ;

@im2sing le ;

table = { ' u i n t8 ' , t o s i n g l e , @im2 uint8

' u int 1 6 ' , t o s i n g l e , @im2u in t 1 6

' int 1 6 ' , t o s i n g l e , @im2 int 1 6

' logical ' , t o s in g l e , @log ical

' double ' , identity , identity

' s ingle ' , ident i t y , identit y } ;

c la s s l n d e x = f ind ( st rcmp ( c lass ( in ) , t ab le ( : , 1 ) ) ) ;

if isempt y ( c l as s l nd e x )

e r r o r ( ' Unsupported input image c l a ss . ' ) ;

end

o u t = t a b l e { c l a s s l ndex , 2 } ( in ) ;

r e v e r t c l a s s = t able { c l a s s l ndex , 3 } ;

[Walter Roberson]

It is a function that is defined in the book the user was using.

Answer 4

[muhammad alli]

https://www.amazon.com/dp/B01GEZN09C

[Walter Roberson]

The reference is to a book "Computational Physics: A Guide For Beginners Looking To Speed Up Their Computation" that appears to have been written by the poster.