Load images faster or create thumbnails from images

In my app, the user takes photos, the photos get stored permanently on the phone. I need the images on the phone to be in their original resolution, which is quite high.
I also have my own gallery-type of page where I display the images like this

img {
    display:block !important;
    max-width:100% !important;
    height:auto !important;

inside a

<ion-col width-33><img src="file:///path/to/image.jpg"></ion-col>

This works fine for displaying the images smaller than they are. But it gets awfully slow to load/display when there are more than than a couple of images on the phone. This is why I need a method that loads the images faster or a method to create thumbnails of the images and store them on the phone.
Does anyone have any ideas how I can fix my performance issue?