histogram doesn't work for .png images?

hello everyone. I am having trouble with displaying histogram for .png image. the image is grayscale already, so I just use this code.

I=imread('38_training.png');
figure,imhist(I)

but the histogram is.. empty.

any idea why? this is the image i'm trying to show the histagram of.

thank you! please help.

Answer 1

[Ameer Hamza]

Your image is binary. It only has white and black pixels. Therefore it only has peaks at 0 and 255. Following example show, it has nothing to do it with png file.

im = imread('pears.png');
imhist(im)

[Lulu Firdaus]

I see. thank you!