Commands for ImageMagick to create thumbnails

Question

Given an photograph uploaded by a user, what is best approach to creating a number various sized thumbnails Using ImageMagick (or GraphicsMagick)? My guess to the steps:

1. Create a super sample of the image, maintaining original aspect ratio
2. Apply watermark to super sample
3. Create the various sized thumbnails using the watermarked super sampled image

Additional requirements:

1. Best quality possible (does this mean PNG over JPG?)
2. Smallest file size possible (does this mean JPG over PNG?)
3. Use density of 72x72, units is ppi

Since I am not that familiar with the intricacies of IM (or GM), some guidance to the best commands that meet my objectives would be highly appreciated. Thanks.

Solution

Check out the ImageMagick documentation:

• For a specific size http://www.imagemagick.org/Usage/thumbnails/#fit
• For watermarks http://www.imagemagick.org/Usage/annotating/#watermarking

The best quality possible is complicated since difference images compress differently. I'm partial to PNG since it has a variety if compression techniques available to allow for experimentation.

Comments

[StackOverflowNewbie]

I'm familiar with the basic commands. As a matter of fact, I can already do what I need to do. The problem is that I am not sure if my approach is the best. There are so many options to ImageMagick.

[John Percival Hackworth]

I'd suggest using the commands recommended in the docs, since they're known to work. Supersampling an image for scaling down is largely pointless.

[Meetai.com]

Better to put those commands here, as it's a headache to read that documentation.