Find JPEG resolution with PHP

Question

Calling all PHP gurus!

I understand that you can use getimagesize() to get the actual pixel height and width of an image in PHP. However, if you open an image in pho

Answer 1

You could just read the JPEG file directly, bytes 14-18 specify:

• byte 14: 01, X and Y density unit specifier (00: none, pixel ratios, 01: DPI,02: DPC)
• bytes 15-16: horizontal pixel density,
• byte 16-18: vertical pixel densit

Also see: http://www.obrador.com/essentialjpeg/headerinfo.htm