http://ace.waytook.com/lab/dpi

Filename		Size				Modification Date		/usr/bin/file's Type Estimation
dpi_300.png		374.2 kb				2011.05.25 18:54:27		PNG image, 2261 x 3011, 16-bit/color RGBA, non-interlaced
dpi_72.png		278.7 kb				2011.05.25 18:54:41		PNG image, 500 x 700, 8-bit/color RGB, non-interlaced
dpi_unknown.png		20459.7 kb				2011.05.25 18:54:41		PNG image, 2261 x 3011, 8-bit/color RGB, non-interlaced
gd.php		0.5 kb				2011.05.25 18:54:27		PHP script text
gmagick.php		1.1 kb				2011.05.25 18:54:41		PHP script text