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

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...

Answer 1

[Friedrich]

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))

[Fangjun Jiang]

Oh, are you suggesting the OP to divide his matrix by 255? It's not necessary. im2double() automatically does that.

[Friedrich]

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

[Fangjun Jiang]

Fair enough! No argument from me!

Answer 2

[Fangjun Jiang]

By simply dividing all the numbers by 255?

See example:

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

[Friedrich]

Little note: you have to cast it as a double first. Otherwise you will get 0 as result, e.g. uint8(10)/255

[Fangjun Jiang]

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]

My comment is related to your statement: "By simply dividing all the numbers by 255?" Simply diving is not enough you have to cast first.

Answer 3

[Pramod Bhat]

Thanks alot friends. ..). thanq. i understood.