What is the formula to convert uint8 image to double format ?

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Pramod Bhat 2011-8-19

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Hi friends, i want to convert a uint8 format image to double format.I have got command 'im2double' for that. But i want to know the basic formula for converting that.

For ex : i want to represent intensity level 256 to double format which is represented in [0 1]. please help. Thanks...

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Answer 1

Friedrich 2011-8-19

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Hi,

simply cast it as double and than divide by the maximum number of the datatype. In your case (uint8) its 255. So when your image is A do

double(A)/255

or more general

double(A)/intmax(class(A))

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Friedrich 2011-8-19

Yes im2double does that but Pramod asked for the basic formula. He knows about im2double.

Fangjun Jiang 2011-8-19

Fair enough! No argument from me!

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Answer 2

Fangjun Jiang 2011-8-19

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By simply dividing all the numbers by 255?

See example:

I1 = reshape(uint8(linspace(1,255,25)),[5 5])
I2 = im2double(I1)

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Fangjun Jiang 2011-8-19

What do you mean? The code I quoted is from help im2double. The OP is asking how im2double is able to convert 0~255 to 0~1. I am guessing it just divides by 255, like you guessed.

Friedrich 2011-8-19