reason for converting image into double

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sandeep kumar
sandeep kumar on 28 Aug 2015
Commented: nabeel raza on 10 Oct 2017
while reading the, why have to convert an image into double format.
  1 Comment
nabeel raza
nabeel raza on 10 Oct 2017
For Example:
I2 = im2double(I);
I2 = im2double(I,'indexed');
I2 = im2double(I) converts the intensity image I to double precision, rescaling the data if necessary. I can be a grayscale intensity image, a truecolor image, or a binary image. If the input image is of class double, then the output image is identical.

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Answers (2)

Matz Johansson Bergström
Matz Johansson Bergström on 28 Aug 2015
Edited: Matz Johansson Bergström on 28 Aug 2015
The reason is precision. Say you read an image using (write this in the Matlab prompt)
>>Im = imread('filename');
The format is integers from 0 to 255. Now if we want to manipulate the image, we can write
Notice that the format is still integer and not double. This means that we have lost precision. All subsequent manipulatins to the matrix Im will be in integer precision, unless we write something like
Im = im2double(Im)

Walter Roberson
Walter Roberson on 28 Aug 2015


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