What is a pixel map?

What a pixel map is for

Unlike a monitor or projection screen, you can't just send content to an LED wall and expect it to show up in the right places. With one screen that's close to the ratio of your input, you can scale to fit. Anything else needs details about how to get the right content into the right place. A pixel map is the document that carries those details.

• Techs double-check that what they're building matches what's been communicated. How many panels wide and tall, and which output feeds what.
• Content creators make content for it, so a logo lands in the middle of the screen instead of across a seam.
• Media server operators load it as an image and slice their composition against it.

Pixel map or output map?

Both words get used for the same picture. When it matters:

• A pixel map is the layout. Which panel sits where, at what size.
• An output map is the file you load into a media server, rendered at the exact resolution of the screen. One pixel in the file is one LED pixel.

The map is the plan, the output map is the file. A 3840x2160 layout downloads as a 3840x2160 image and drops onto the output without scaling. We use these interchangeably, but if you want to be precise, that's the difference.

Is pixel mapping the same as projection mapping?

No.

Projection mapping throws video onto a physical object with projectors. A building, a car, a set piece. The work is warping the image so it lines up with the surface, which is what tools like MadMapper are for.

LED panel mapping starts from the opposite place. The pixels already exist, in fixed positions, in a grid you picked when you specified the panels. Nothing is being warped onto anything. You're describing hardware that's already there and how to get the content to show up in the right place.

Is it the same as pixel tape mapping?

Also no, though both get called pixel mapping and the shared name causes real confusion.

Pixel tape mapping, often just called pixel mapping, deals with individual addressable LEDs on a strip. Each LED gets a position and the map tells the controller which one to light. It turns up in architectural work, scenic detail, and hobby builds, with tools like Madrix, xLights and WLED.

LED panel mapping works a level up. The unit is a whole cabinet with a resolution of its own, arranged into a screen that plays video. Same phrase, different scale, different tools.

The three kinds of mapping, side by side

What's on a pixel map?

There's no standard. Most useful maps carry the same things:

• The panel grid. Every cabinet drawn at its real proportions, so the picture matches what gets hung.
• Coordinates. Each panel labelled by column and row, written col,row to match the usual x,y convention.
• Screen names and resolutions. A header per screen, so a map with three screens on it doesn't need a second document to explain itself.
• Blanked panels. Screens aren't always clean rectangles. Panels that aren't there get switched off rather than faked.

Transparent walls are a special case

Transparent LED walls are see-through, and they don't all get there the same way. Some skip every other row of LEDs. That makes the vertical pitch double the horizontal, commonly 3.9mm across and 7.8mm down, so a physically square area lands on a pixel grid half as tall as it is wide. Others, like regular 7.8mm, have the same pitch in both directions and need no special treatment.

A map for the uneven kind gets squished vertically to cancel the stretch the screen applies. It looks wrong on your monitor and right on the real screen. The anamorphic page covers the mechanism.

Making one

HappyMaps is a free pixel map generator that runs in the browser. Pick your cabinets, arrange the screens, download a PNG at full resolution. Getting started is the two-minute version, or open the generator and start building.