dinasaurusrex

It is true that the time to fetch, render, and deliver an image the first time it is requested can be a bit longer, because of all the processing we're doing in the case of that single request, but because we then cache that fetched image, all subsequent requests are delivered an order of magnitude faster (50th percentile 45ms).

The majority of the time taken in the first request is actually in fetching the image from the origin source, so once it's cached in our system it becomes a much faster operation: and of course delivering the cached image without it traversing our stack is even faster.

So yes, the initial request can take time, but all of the subsequent requests of that image are much faster than the alternative. And when you take into account that our service makes it possible to send the correctly sized image for the display (instead of loading a preset size and displaying it smaller), and optimal file types based on device and browser (webp for chrome, etc), load times/page weights on all of those requests are significantly improved.

In general, anyone who serves multiple requests for their images over time will see a marked improvement on page weight/speed, compared to rolling their own solution where they have preset image sizes and deliver jpeg only.

(full disclosure: I work at imgix)

Uploading pre-edited images takes time/resources, and in general a lot of our customers rely on us to do all of their image processing so that they don't have to.

Additionally, creating edited versions of images in advance presents two problems: 1) Any future site redesigns or edits must now be applied en masse to the existing images or risk older images not complying with the new scheme, and 2) Instead of only managing the one original source image in the origin, now we're talking about maintaining all of the different edited versions, which is very inefficient from a storage and image management perspective.

There are many advantages to applying all of the image transformations on-demand, rather than in advance. Keep in mind that we are not simply photo filters, but a full end-to-end image processing offering (which applies everything from simple photoshop edits like cropping, face detecting, color correction, watermarks, etc. to automatic content negotiation and automatic resizing/responsive design) that works on the fly; this means that our customers now can make batch edits to their entire corpus of images through a few simple code edits.

This can become extremely cost-effective, but also helps in reducing page weight significantly.