In part one (One pixel is worth three thousand words) of this turned-to-be-two-part blog post, I discussed one-pixel images and how well different image formats “compress” these images. I was surprised how much there is to be said about the matter. This was supposed to be a short blog post, describing one-pixel images and how they compress, and instead it became a glorious monster (and also a two part blog post…).
A couple of months ago while taking a break from implementing cool new features like q_auto and g_auto, I was joking in our team chat about how well various image formats “compress” one-pixel images. In response, Orly — who runs the blog — asked me if I’d write a post about single-pixel images. I said: "Sure, why not. But it will be a very short blog post. After all, there’s not much you can say about a single pixel."
Every image is unique and every one of your website visitors is different. In a perfect world, we'd like to adapt each image individually to be "just right" for every user. With "just right" being perfectly cropped, using responsive dimensions, correct encoding settings and optimal quality with the best image format.
As a developer, you want to allow your users to download multiple files in a single click. An easy way to download multiple files and share them is to generate a ZIP file. When images are involved, you may also want to normalize the original images before including them in the ZIP file, by scaling them down to the same maximum resolution or converting them to the same format.