Fidelity in images is about visually preserving the original; appeal is about hiding the compression artifacts. Depending on your priority, you would compress images with either of these approaches to reduce the file size while still maintaining a reasonable level of visual “quality”:

GUESS? Inc. designs, markets, distributes, and licenses a lifestyle collection of contemporary apparel, denim, handbags, watches, eyewear, footwear, and other related consumer products. These products are distributed through branded GUESS Stores, as well as department and specialty stores around the world, and via e-commerce sites available to 55 countries. GUESS websites act as virtual storefronts that both sell their products and promote their brands, showcasing products in an easy-to-navigate experience that allows customers to see and purchase from its collections.

Think about the last time you bought something online—and about the last time you did that but what you purchased wasn’t something you were after when you opened your browser. What captured your attention in the search results, the assortment page, or the product page that convinced you to make the purchase?

With Cascading Style Sheets (CSS), you can style your site and transform the related images. For example, you can create static or sticky positioning for the graphics, define backgrounds and borders, resize, and create cool filters to show off the artistry.

Resizing images with JavaScript (JS) creates nifty effects, many of which you cannot do in Cascading Style Sheets (CSS). However, even though you can automate a zoom effect with JS to enable users to zoom in and out of images, limitations abound.

With JavaScript (JS), you can create cool image animations, which are difficult to do with Cascading Style Sheets (CSS). This article describes how to—
Here are the topics:
To rotate images with JS, edit the CSS transform
property. See the procedure below.

Image effects, which you can set up with CSS, define how images are served to users. This article describes how to create basic effects, image hover, and animated images through parameter configurations in your main CSS stylesheet and—much faster and dynamically—in Cloudinary.
Here are the topics:

With Cascading Style Sheets (CSS), you can change the size and aspect ratio of images and backgrounds. Three resizing options are available: absolute resizing, retention of the aspect ratio, and relative resizing. You can also scale and fill backgrounds. However, those are all manual chores that take time, skill, and effort.

CSS image overlays are a common technique for transposing text or images over each other. For example, you can combine images and text on a website when captioning an image, or place a live text element over a button.

When it comes to quality versus quantity, you’ll often hear people say, “It’s the quality that counts, not the quantity”. While that’s true in many situations, there are also cases where you want both quality and quantity. You may have thousands of images on your website and you want them all to look great. This is especially important if your website allows users to upload their own content, for example, to sell their own products or services. You don't want their poor quality images to reflect badly on your brand.