I can't open this PNG file with imagecreatefrompng()

Question

Here is a PNG file: http://imgur.com/NUl4v.png (Yes, never mind that it's a funny penguin with a sign...)

When running the following code:

imagecreatefrompng('http://imgur.com/NUl4v.png');

I get an error:

PHP Warning: imagecreatefrompng() [function.imagecreatefrompng]: Cannot read image data in /home/test/...

The PNG file seems to be fine - I can open it with different editors, and the Unix file command reports that it is:

PNG image, 640 x 360, 8-bit/color RGB, non-interlaced

PHP version: 5.2.13
GD version: bundled (2.0.34 compatible)

Answer 1

I have no idea why, but the following works:

imagecreatefromstring(file_get_contents('http://imgur.com/NUl4v.png'));