GD и функции для работы с изображениями Функции
PHP Manual

imageresolution

(PHP 7 >= 7.2.0)

imageresolutionGet or set the resolution of the image

Описание

mixed imageresolution ( resource $image [, int $res_x [, int $res_y ]] )

imageresolution() allows to set and get the resolution of an image in DPI (dots per inch). If none of the optional parameters is given, the current resolution is returned as indexed array. If only res_x is given, the horizontal and vertical resolution are set to this value. If both optional parameters are given, the horizontal and vertical resolution are set to these values, respectively.

The resolution is only used as meta information when images are read from and written to formats supporting this kind of information (curently PNG and JPEG). It does not affect any drawing operations. The default resolution for new images is 96 DPI.

Список параметров

image

Ресурс изображения, полученный одной из функций создания изображений, например, такой как imagecreatetruecolor().

res_x

The horizontal resolution in DPI.

res_y

The vertical resolution in DPI.

Возвращаемые значения

When used as getter (that is without the optional parameters), it returns TRUE on success, или FALSE в случае возникновения ошибки. When used as setter (that is with one or both optional parameters given), it returns an indexed array of the horizontal and vertical resolution on success, или FALSE в случае возникновения ошибки.

Примеры

Пример #1 Setting and getting the resolution of an image

<?php
$im 
imagecreatetruecolor(100100);
imageresolution($im200);
print_r(imageresolution($im));
imageresolution($im30072);
print_r(imageresolution($im));
?>

Результат выполнения данного примера:

Array
(
    [0] => 200
    [1] => 200
)
Array
(
    [0] => 300
    [1] => 72
)

GD и функции для работы с изображениями Функции
PHP Manual