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

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jagannath mishra
jagannath mishra 2013-3-10
评论： 玉山 邓 2021-1-29
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);

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Walter Roberson
Walter Roberson 2013-3-10
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
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jagannath mishra
jagannath mishra 2013-3-12
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
Image Analyst 2013-3-12
编辑：Image Analyst 2013-3-12
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');

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更多回答（3 个）

Steve Eddins
Steve Eddins 2013-3-11
tofloat is a function provided with the book you are reading. You can find it in Appendix C on page 806.
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Kiranraddi morab
Kiranraddi morab 2013-3-13
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
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PRABAKARAN K
PRABAKARAN K 2019-10-24
编辑：PRABAKARAN K 2019-10-24
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 } ;

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muhammad alli
muhammad alli 2016-6-13
编辑：Walter Roberson 2019-10-24
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Walter Roberson
Walter Roberson 2016-6-13
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.

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