Alternative for phpthumb or slir

I used phpThumb before. Then switched to slir. I still prefer slir with less memory usage, and re-written url. However, slir is not working with external images.

For example, if pointing to /slir/w150/http://external-domain/path-to-image.jpg, it will look into http://my-domain/path-to-image.jpg

Is there any other recommendation for image thumbnail generation please? Searching on google brings some options, but I want to hear from real experiences.

Thanks.

I use imagemagick for all my image modifications and it will work with external files.

Thanks. However, I should add more details that I prefer GD, cause not all servers have imagemagick by default.