Image overlays, and how to size them

An overlay is your own image sitting on top of the board while the flaps keep flipping underneath. It is how a board stops looking like a generic display and starts looking like yours, without touching a single line of the text.

Start with the easy one. A graphic in a corner, along the bottom, or down one side: a logo, a header strip, a bit of colour that matches the room. The picture is mostly empty, around ninety per cent transparent, and only the part you want to see is filled in. The board shows through everywhere else, so nothing you have written is hidden and you can leave the same overlay in place while the content changes underneath it all day.

Once that is working, the more ambitious version is a full-screen image. Instead of clearing most of the picture, you take the whole thing and turn its opacity down, commonly to somewhere around forty to sixty per cent transparent. The image covers the entire board and the flaps read through it, so you get a photograph and your text in the same frame rather than one or the other. It is the difference between a board with a logo on it and a board that looks designed.

So there are three kinds of image in play, and it is worth knowing which one you are making. A normal overlay is mostly empty, roughly ninety per cent transparent, with artwork in one area. A full-screen overlay covers everything and is turned down to around forty to sixty per cent so the board shows through. A picture board is a different thing again: the image is the content rather than a layer over it, and that has its own page.

Sizing is the part that catches people out, and it is simpler than expected. Design the image at exactly the size of the screen it will run on. For a full HD TV that is 1,920 by 1,080 pixels. Match the screen and every edge lands where you drew it.

Overlays must be PNG, because PNG is the format that carries transparency. A JPG has no transparent areas at all, so it arrives as a solid rectangle and hides the board completely. Picture boards can be PNG or JPG, since nothing needs to show through them.

If your image is bigger or smaller than the screen it will still work, it just gets stretched to fit. Nothing breaks. But anything you positioned carefully moves, and a logo drawn crisply at the wrong size arrives soft, which is why matching the screen is worth the two minutes.