What is the benefit of casting image into double after reading in Matlab

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Tahir 2015-2-16

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https://ww2.mathworks.cn/matlabcentral/answers/178741-what-is-the-benefit-of-casting-image-into-double-after-reading-in-matlab

评论： Image Analyst 2015-2-16

Hello, I asked several questions here.in every answer it is recommended that caste the image to double.

So i want to know what is the benefit of casting image to double. My segmentation results are not good.so i am thinking on every factor. plz help.Thank you

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Answer 1

Image Analyst 2015-2-16

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It's not necessarily true that you should cast to double. It depends on the circumstances and what you're trying to do or measure. I don't think it should make the segmentation worse though.

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Tahir 2015-2-16

在 MATLAB Online 中打开

Ok sir i want to know that this function input should be in double or unit8.This is my first operation on my medical image image. The image is also attached here.

   function img_BlueRation = Fun_BlueRationConv(img)
    R = img(:,:,1);
    G = img(:,:,2);
    B = img(:,:,3);
    img_BlueRation = ((100 * B)./(1+R+G)) .* (256./(1+B+R+G)); 
  end

Kindly sir also tell me what is clipping in this sense.

Image Analyst 2015-2-16

在 MATLAB Online 中打开

Just make a little experiment to see. Look at this code and see the two different results:

R = uint8(9);
G = uint8(19);
B  = uint8(139);
img_BlueRation = ((100 * B)./(1+R+G)) .* (256./(1+B+R+G))
whos img_BlueRation
R = double(9);
G = double(19);
B  = double(139);
img_BlueRation = ((100 * B)./(1+R+G)) .* (256./(1+B+R+G))
whos img_BlueRation
img_BlueRation =
   18
  Name                Size            Bytes  Class    Attributes
    img_BlueRation      1x1                 1  uint8              
img_BlueRation =
          730.377668308703
  Name                Size            Bytes  Class     Attributes
    img_BlueRation      1x1                 8  double