How to Check Photo DPI with PHP

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.

Found it for JPEG: http://stackoverflow.com/questions/262090/find-jpeg-resolution-with-php/262117#262117 — Slava, May 05 '11 at 07:15

score 17 · Answer 1 · edited Jun 15 '13 at 14:24

17

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.

edited Jun 15 '13 at 14:24

Alain Tiemblo

36,099
17
121
153

answered Oct 20 '12 at 12:58

Naeem

179
1
3

4

Interesting input! But to which file types does this approach apply to? – SquareCat Nov 16 '12 at 06:26
it works for jpg format, look at denisb's comment at [bytes.com](http://bytes.com/topic/php/answers/5948-dpi-php-gd) – Alain Tiemblo Jun 15 '13 at 14:29
Hello there, I created a 300DPI JPEG via Photoshop, but the above function returns 42 DPI. – Raptor May 17 '19 at 07:36

score 2 · Accepted Answer · answered May 05 '11 at 04:53

2

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.

answered May 05 '11 at 04:53

Alix Axel

151,645
95
393
500

How to Check Photo DPI with PHP

2 Answers2

Linked