Zena has advanced image handling possibilities. You just upload your image and it is automatically resized to be displayed in the different context where you use it.
image formats
You define image formats globally for your website using a simple interface:
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You can then use these formats to display images either in templates (see img zafu tag) or inside your articles (see inserting images).
[to be continued]
In the mean time, we have a video showing this.