I use OmniGraffle Pro for simple diagrams, meaning objects connected to each other with simple lines. It's easy to do this in OGP as each object used (images, icons, the like) receives automatically connection points that act as magnets. Once a connection with a line is established at any of these magnet points, moving the object around on the canvas moves flexibly the connection lines with it. Very useful. Some people try to draw similar diagrams with Powerpoint instead, but the sheer absence of magnets in Powerpoint makes it really hard.
In terms of objects OmniGraffle offers a large variety (object types and connection lines) and it's Mac version also offers a large collection of Apple artifacts. Problem is, what happens with other objects? Well, this is what I'll describe here to remember if I need to do this again.
As a matter of illustration, suppose I needed an image that looked like my own simple HDMI Switch, for instance. Here are the steps:
- I go to Google images and put 'HDMI switch' in the search field. A myriad of images appear. I scroll around and pick one that looks almost identical with what I was looking for.
- I drag and drop this image into Photoshop. Photoshop puts the image on its background layer. Double clicking it creates a new layer and background is no more. I want to get rid of all white space next, and create transparency instead. This can't be done when the image stays on the background layer.
- After the image becomes a regular layer, I use the Magic Wand to select all the white space surrounding the object. I do the necessary to select it all. I then hit backspace, the white disappears, and is replaced by the transparency surface symbols. That's it.
- If cropping needs to be done, I do that next. I then save the image as a PNG file that I know maintains transparency. It's a good image format that PNG, although for plain vanilla small size file format for the web, I'd still select JPG instead.
- Job done. I drag and drop the newly saved image PNG onto the diagram and there you go. If now one object gets obscured by another and the latter maintains its transparency the result will be a lot more pleasing, as the obtained transparency will allow parts of the former (the obscured) to appear behind the latter (the obscurer) in a more natural way, and not behind the white frame that a JPG format would have caused (even with strict cropping).
- Another hint. Magnets are positioned on an object's frame contour, and, unless you crop it close to the actual object, you risk to have your connections hanging in the air, at a distance (example: see the lines with arrows pointing to the Plasma TV above). In that case, you can create another new object with its own magnets (I prefer a text block), and position it inside the original object (see the white text 'HDMI switch' in the image to the right of the TV above). Connect next your lines with the magnets on that text object rather than the image's.
I don't believe there's any object for all practical purposes that Google Search won't return, if you describe the criteria properly, that is. I was able to find pictures of the most improbable devices. Trust me on this. Amazing what these guys can go find for us to use. Good stuff. Now, in the unlikely event you can't find something, or you don't like the image Google served you with, then, all it takes is to shoot an image of the object by yourself. Put it against a white background (or any monochromatic so you can pick it up easily with reasonable small range pixel tolerance when using the magnetic wand), light it up well without shadows, shoot the frame and process it, and continue from step 2.