Issues with greyscale png images in matlab

I have a number of greyscale png images of faces (from a free dataset) that I am using as part of a Psychtoolbox experiment. In photo apps such as preview they all look okay, but when I open them in MATLAB several of them are pixelated and the colours are off so they are unusable (see attached photos). Any suggestions as to why this might be?

Thanks!

[Rik]

Can you attach the image as a file and post the code you used?

[Caroline Harbison]

myimage = imread('F1.png');

imshow(myimage)

Answer 1

[Dave B]

This looks like the result of loading an indexed image, you can read the colormap using the second output of imread:

[img,cmap]=imread('image.png');
imshow(img,cmap)

Or you can convert it to an rgb image using ind2rgb:

img_rgb = ind2rgb(img,cmap);
imshow(img_rgb)

[Caroline Harbison]

That worked, thanks so much!