How to resize image on touch devices?

In the mobile browser version Vkontakte m.vk.com implemented image scaling on touch devices and on the desktop using the mouse wheel.
To figure failed, I would like to know how this is done.
August 19th 19 at 23:11
2 answers
August 19th 19 at 23:13
JS'om changing the width and height of it , nothing complicated
August 19th 19 at 23:15

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