set the color of the emerging (empty) area of generated thumbnail. Leave it empty for transparent background.
This allows to remove unwatend empty space around uploaded image:
Compress images to reduce image file size and improve page load time.
Convert to JPG format
Convert images to JPG to boost page load speed.
Enable WebP format
WebP is the rockstart of image formats. Using WebP can dramatically reduce image file size while preserving the same quality and transparency. WebP format is widely supported by all modern browsers, otherwise, it fallbacks automatically to standard image.