I'm a web developer, so I don't do any advanced graphic design, but I have to work with images all the time. I'm given a mockup and I have to copy/paste images into a program (for years I used Fireworks), and often all I'm doing from there is exporting the image in the right format (jpg, png, svg, etc.). In Fireworks, if I have an image in my clipboard, when I choose File->New, I get a canvas that is the same size as the image in my clipboard. So all I do is paste the image, which lands perfectly into that canvas, and I'm ready to export immediately.
When I do some of the basic graphic design I'm sometimes asked to do, like create a banner with an image and some text, it's wonderful to be able to "Trim Canvas" and have the canvas size downward to whatever I've built, or "Fit Canvas" where the canvas will grow so that anything larger I've pasted into it will be contained in the canvas. I would love to see these features in AD.
That said, the procedure to follow in AD to get your artboard tight around your image or design so that you can export it is:
1. Delete all artboards, keeping all objects
2. Ctrl+A (select all)
3. Click the Artboard Tool button in the left column.
4. In the "Artboard" option row that appears above the design, choose "Selection" from the "Size" dropdown menu (Once you've done this once, it defaults to it next time)
5. Click "Insert Artboard" which is right next to that.
Now your canvas (artboard) will be perfectly fit to your image or design and you are ready to export.
I know from reading this thread that I'm not the only one who would like this functionality. Since it does involve an exact set of steps that already exist in AD, and these exact same steps are repeated each time, it seems like there could be a button, or a hot-key combination, built without too much trouble. I would add a lower-right tiny triangle to the Artboard Tool button and call the option "Trimmed Artboard Tool".
