Read attachment data

If i read the data out of the media library it returns a encrytion:

a:6:{s:5:"width";s:4:"1680";s:6:"height";s:4:"1050";s:14:"hwstring_small";s:23:"height='80' width='128'";s:4:"file";s:17:"2009/12/blaba.jpg";s:5:"sizes";a:3:{s:9:"thumbnail";a:3:{s:4:"file";s:17:"blaba-150x150.jpg";s:5:"width";s:3:"150";s:6:"height";s:3:"150";}s:6:"medium";a:3:{s:4:"file";s:17:"blaba-300x187.jpg";s:5:"width";s:3:"300";s:6:"height";s:3:"187";}s:5:"large";a:3:{s:4:"file";s:18:"blaba-1024x640.jpg";s:5:"width";s:4:"1024";s:6:"height";s:3:"640";}}s:10:"image_meta";a:10:{s:8:"aperture";s:1:"0";s:6:"credit";s:0:"";s:6:"camera";s:0:"";s:7:"caption";s:0:"";s:17:"created_timestamp";s:1:"0";s:9:"copyright";s:0:"";s:12:"focal_length";s:1:"0";s:3:"iso";s:1:"0";s:13:"shutter_speed";s:1:"0";s:5:"title";s:0:"";}}

How can i decode this, i thought i could be done with json_decode, but that didnt do the job?

Is it also possible to check the image if its used in a post ?