James Taylor wrote:

I think there is a question about whether swapping from inside PHP to ImageMagick and back is a good thing or not - why spawn a separate process to do essentially the same work?

Another possibility is:

1. Load image.
2. Create new image to store text in
3. Render text (make it vector based if possible)
4. Resize-text-image to being correct size/proportion
5. Merge text-image over image

The actual processing is slower than the spawning, so it's not particularly a problem, but I am moving towards using the Imagick PHP libraries which will bring the processing inside PHP rather than spawning a new process.

Spawning a process has the advantage that I can experiment at the commandline first (and can seek advice from a wider range of people), but the options are pretty straightforward to convert between library and commandline.