Hello Ivan.
I think you are messing with the images.
You can see the sizes of the images by accessing preferences -> Images
When you upload an image, prestashop creates as many images as are necessary to show the products (Thumbnails, average image, etc…), that is, it creates the images with the sizes that you have configured in preferences -> Images
If the image is larger, it resizes it until it fits and if it is smaller, instead of resizing it, it will show you the original size.
At least you have to upload the image in the largest size that you have in preferences -> Images and as I already told you, all the images that you upload must have the same size, both in height and width.
All the best
Answered : 09/11/2017 6:12 pm