Delivering images in an optimized fashion for the variety of devices and browsers available is as much a strategic decision as it is a technical one.
Providing the best possible image can be challenging, particularly when thousands or more images are in play. Fortunately, there's no shortage of insights into image optimization and solutions to reduce the complexities surrounding it.
Cloudinary, for example, just announced several "automated" enhancements to its image management solution, most notably content- and context-aware image adaption capabilities.
The cloud-based image an video management system now supports automatic content-aware cropping (similar to what Adobe recently introduced), content-aware encoding (automating the file size versus quality trade-off decision), dynamic format selection (optimizing image delivery by selecting the most efficient format based on the image's unique content and the viewing browser), and automatic responsive images (at the CDN level).
There are numerous alternatives to Cloudinary if you're in the market for an image processing and optimization solution including imgix, blitline, resrc.it and others.