Context
CarTrawler delivers car rental inventory from up to 2,000 providers to nearly one billion passengers annually. The car imagery library was being overhauled to deliver consistent, high-resolution images at scale — and the team saw an opportunity to add dynamic coloring, something that had always been written off as unachievable.
Challenge
Serving every car in every possible colour would require storing and managing thousands of image variants per model — an approach that didn’t scale. Any solution also had to add zero overhead to the front end: no extra JavaScript, no CSS tricks, no additional image requests.
Approach
Working with imgix, we designed a two-layer compositing technique. A base car image sits underneath a transparent “paint layer” covering only the areas to be coloured. Using imgix’s monochrome and watermark parameters, the paint layer is colourised on the fly and composited over the base — all within a single image URL. The last six characters of the URL control the hex colour value.
Outcome
Cars can now be dynamically coloured at the CDN level with no front-end changes. The approach scales to any colour without storing variants. imgix published it as a case study, and the technique was picked up by teams working with other product categories beyond cars.