^{Originally posted by john-parton January 20, 2024}
The webp API supports saving with a "target_size" parameter to limit the maximum size of the resulting file.

int target_size;        // if non-zero, set the desired target size in bytes.
                        // Takes precedence over the 'compression' parameter.

https://developers.google.com/speed/webp/docs/api

As far as I can tell, this isn't exposed in libvips (and consequently pyvips, the binding I am using.)

This is a useful feature for my use case. I preprocess images before they are sent to CloudFlare Images. They have specific limits for resolution, but also an overall limit for file size. In my case, I set images to be at most 6,000 x 6,000 pixels and am saving with Q=90. For the vast majority of images, that's fine, because the resulting image is usually significantly less than 10MB, but for some noisy images with difficult to compress features, it just barely goes over the 10MB boundary.

If I could just pass this in, I wouldn't have to worry about, but now I'm faced with having to either:

1. Lower my resolution and Q factor for all images
2. Check the resulting output size every time, and then adjust either the resolution or Q factor if it's in excess of 10MB.

I wouldn't really consider either of these to be a good solution.