how to convert a double matrix image to a unit8 matrix ?

Hi everybody :) I have an image ,a matrix with values between -0.0934 and 0 and i want to convert it to unit8 matrix with values between 0 ans 255.

Answer 1

[Azzi Abdelmalek]

A=imread('yourimage')
B=uint8(A)

EDIT

d=linspace(min(im(:)),max(im(:)),256)
im1=uint8(arrayfun(@(x) find(abs(d(:)-x)==min(abs(d(:)-x))),im))

[Mariem Harmassi]

I already have read the image then preprocee it and it's saved as a matrix all the pixels are negatif or null .whan i directly perform the unit8 function,the result is black image . i have also tried this code : u=abs(z); u=u*255; imshow(u) the result is the inverse graysclae of the preprocessed one.i also tried this: u=1-abs(z); u=u*255; imshow(u) I obtained a white image

[Azzi Abdelmalek]

It's not unit8 function it's uint8

[Mariem Harmassi]

yes i tried uint8 it was just an error

[Azzi Abdelmalek]

Try this

%If im is your image
d=linspace(min(im(:)),max(im(:)),256)
im1=uint8(arrayfun(@(x) find(abs(d(:)-x)==min(abs(d(:)-x))),im))

Answer 2

[Image Analyst]

You can use the mat2gray() function:

image8Bit = uint8(255 * mat2gray(floatingPointImage));

It will scale your values to the range 0-255.

[Mariem Harmassi]

ohhh thank you lot it s exactly what i need :))))))

[Image Analyst]

Mark it as Accepted then.

[Nhat Nguyen Thanh Minh]

Thanks Image Analyst !

[AKSHAY VARSHNEY]

Sir Could please explain a little bit about the code that you have written for conversion of double into Uint8.

[Image Analyst]

mat2gray() maps the lowest value of the array to 0, the highest value of the array to 1, and everything in between linearly between 0 and 1. The output is a n array of the same dimensions as floatingPointImage.

If you then multiply this by 255, now the output matrix will go from 0 to 255, but it will be double, and some numbers may have fractional parts.

So, to make it a pure integer, I cast it to uint8 with the uint8() function. If you had wanted a 16 bit image (instead of an 8 bit image), you'd have used 65535 and uint16().

[harrynecek]

Sir ImageAnalyst thank you very much for your contribution to this comunity. Everytime I find your answer I know it's gonna be on spot.

Sorry but didn't you ment 65536 for int16?

Can I have one additional question - I'm doing an image compression and every time I do some mathematical operation to a uint16 matrix, it automatically convets it to a double with floating point numbers. Than things like RLC stoppes working.

[Rafee Muhammad]

Thank you so much sir

[Image Analyst]

Harry, yes it should have been 65,635 instead of 16525. Not sure why I typed that but I fixed it - thanks for catching it. It would not be 65536 because even though there are that many values, they start at 0 and end at 65535.

I'd have to see your code to determine why casting it to 16 bit produces a double. Both im2uint16() and uint16() produce uint16 variables, not doubles.

[Juan Manuel Miguel]

Thank you, it was perfect for me!!

[Bruno Aravena Pérez]

Thanks!