How to Check Photo DPI with PHP [duplicate]

Question

Possible Duplicate:
Get/set DPI with PHP GD/Imagick?

Is there a possible way to check photo dpi with php. I have 300 dpi and 72 dpi photos. but wants a way to calculate dpi automatically.

Answer 1

It's too late for me to check now but I think you're looking for Imagick::getImageResolution() and Imagick::setImageResolution() if you need to change the DPIs.

I don't think this is possible with GD, I believe it "converts" all images to 72 DPIs.

Answer 2

If you want it without Imagick or GD Library. I was struggling with this, and since I found it, here you go.

function get_dpi($filename){
    $a = fopen($filename,'r');
    $string = fread($a,20);
    fclose($a);

    $data = bin2hex(substr($string,14,4));
    $x = substr($data,0,4);
    $y = substr($data,4,4);

    return array(hexdec($x),hexdec($y));
}

and then print the array or do with it what you want.