The general rule is to use JPGs for photographs, images that don’t have a transparent background, and other memory intensive files. And to choose PNGs for graphics, files with transparent backgrounds, and other images where clarity and color vibrancy are important.The general rule is to use JPGs for photographs, images that don’t have a transparent background, and other memory intensive files. And to choose PNGs for graphics, files with transparent backgrounds, and other images where clarity and color vibrancy are important.