Convert 32 bit image to 8 bit image

Hey,

I have an .tif grayscale image with a bit depth of 32. I want to convert it from 32 bit to 8 bit. I tried using mat2gray, but every time I tried displaying the image after converting it, it didn't look at all like it before. It was all black with only a few barely visible brighter spots. Does anyone know ho to properly perform the transformation?

Answer 1

[Walter Roberson]

IMG8 = im2uint8(IMG);

Answer 2

[James Tursa]

I'm assuming you just need to scale things. E.g.,

X = your image (as a unit32?)

Y = uint8( double(X) * ((2^8-1)/(2^32-1)) );

There may be a MATLAB function for this, but I am not familiar with the image manipulation functions.

Answer 3

[Image Analyst]

The mat2gray() approach would be this:

To turn it into a double image:

% Scale so min -> 0, and max -> 1.0
dblImage = mat2gray(uint32Image);
imshow(dblImage);

To turn it into an 8 bit uint8 image with the lowest gray level a proprotionally scaled value

% Divide by max so min = something, and max -> 255.  Something is not 0 unless the min was 0.
uint8Image = uint8(255 * double(uint32Image) / max(uint32Image(:)));
imshow(uint8Image);

To turn it into an 8 bit uint8 image with the lowest gray level at 0

% Scale so min -> 0, and max -> 255
uint8Image = uint8(255 * mat2gray(uint32Image));
imshow(uint8Image);