how to convert matrix to graysclae image?

Hi, I have a matrix that i have extacted using spin images descriptor, it is of size 15x15 :

I want to display it in gray scale but it doesn't work. I tried to use imshow() like this :

imshow(uint8(spinImages(1,1).spinIm),'DisplayRange',[0 255])
imshow(255-uint8(spinImages(1,1).spinIm),'DisplayRange',[0 255])

and also i used imagesc :

imagesc(255-uint8(spinImages(1,1).spinIm), [0 255])
imagesc(1-uint8(spinImages(1,1).spinIm), [0 255])
imagesc(uint8(spinImages(1,1).spinIm), [0 255])

but worthless. pleaz could you help me.

[Adam]

If you just try to convert to uint8 it will clip all values above 255 to 255.

You can use a greyscale colourmap with any range of data so why do you need to try manipulations with uint8?

I don't use imshow so can't remember what it expects, but

imagesc( spinImages(1,1).spinIm );
colormap( gray );

ought to work, though I would apply the colourmap explicitly to the correct axes/figure rather than implicitly, but that is just an aside.

You can use caxis if you want to specify the range for the colourmap.

[jiji hr]

It gives me this :

how can I get the bacground in white ? I am sorry I am not verry used with Matlab. And thank you so much for help.

[jiji hr]

Thank you i Found it, it was :

imagesc(255-uint8(spinImages(1,1).spinIm));

Thank you so much for help.

[Guillaume]

As has been pointed out by Adam and I, by converting to uint8 you're clipping all the intensities above 255. This means your 262 will appear exactly the same as the 1232 and 3906 and many more.

[Adam]

imagesc( spinImages(1,1).spinIm );
colormap( flipud(gray) );

will give you a white background and high values as black if that is what you want visually.

Obviously you can also inverse the data itself - it depends if you want the data inverted for other purposes than visualisation too.

[jiji hr]

that is great it works for me. thak you so much.

Answer 1

[Guillaume]

" but it doesn't work". In what way?

What you've showed will display the image, possibly not the way you want, but it will display it.

I'll note that the intensity range in your screenshot is up to 3906. Because of the call to uint8, any intensity above 255 will be set to 255. I'm not sure that's what you want.

There's certainly no reason to convert to uint8 if you're going to restrict the display range to [0 255] anyway.

Possibly, you meant:

imshow(spinImages(1,1).spinIm, [])

[jiji hr]

Actually Yes you are right I didn't express it very wel, it displayes but it is not what I was searching about. thank you for your collaboration.

[Guillaume]

If you want to inverse the image:

imshow( max(spinImages(1, 1).spinIm(:)) - spinImages(1,1).spinIm, [])

would be better than the completely unnecessary conversion to uint8.

[jiji hr]

Your answer works well too for me thank you fo help.