The PrestaShop script starting from the version 22.214.171.124 enables the administrator to select the quality of product images.
You can upload the product images through your PrestaShop admin area. In the admin area, go to ‘Catalog’, select a product and open the ‘Images’ tab in order to browse and upload product images.
You can change the quality of your product images through PrestaShop admin area >> Preferences >> Image.
Here you can set the JPEG and the PNG quality image values through the defined options. If you select the minimum graphic level of the images, it will result in shorter website and image loading times. Therefore, if you are running a large online store with a wide range of products, you can consider reducing the image quality in PrestaShop and this will further improve the complete website performance.
Once you have defined the image values, click on the ‘Regenerate thumbnails’ option. Allow sometime for the upload of products to be completed. After this, you can clear your browser cache and check the final result.