How-To: Build Your Own Mosaic Poster (Part 1 of 2)

February 2, 2013
Mosaic Panorama

Several months ago, I moved to Montréal and found a great apartment. The ceilings are high and the floor is wooden, but my walls have remained largely blank. For months I've been trying to decide how to decorate them, and I think I've reached the age where another "Dark Side of the Moon" poster does not add much character to my abode.

I knew I wanted something large and dramatic when people walked into my room. I had heard of a piece of software years ago that let you print out an image across many sheets of paper, allowing you to 'blow up' the image into a large poster. With another piece of software I've used over the years, I've been able to create some pretty outstanding mosaics from my photos.

This project is a combination of these two pieces of software. How long did it take? How much did it cost? How hard was it to do?

In this first of two posts, I'll detail how to plan your poster and create your mosaic. In the second post, I'll explain how to properly print and mount your piece.

Let's get started.

Step 1: Determine Your Poster's Size

To the left and right of my room's faux fireplace, there are two blank walls which contain a wooden frame. I have no clue what these wooden borders were used for in previous decades, but they serve as a perfect limitation for my poster. In my case, they measured 72" high by 36" wide. Obviously, your dimensions will differ, but it's very important to know exactly how big you want your poster to be, as we will be using these dimensions to crop your photo.

Your dimensions will also affect what image you would like to use. For my dimensions, a city skyline would not be appropriate, but a picture of a skyscraper just might be a good fit.

Step 2: Download MacOSaiX

We will be using a piece of free software called 'MacOSaiX' to generate our mosaic image. When I first used MacOSaiX in 2005, I was blown away. So much so, I generated a mosaic from a portrait of a girl I liked at the time and sent it to her. Her mother wanted to frame it. 

The girl found it... interesting.

Nevertheless! I'm still blown away by MacOSaiX. You can download it here.

I have also found a similar version for Windows called 'AndreaMosaic'. Unfortunately, the rest of this how-to will focus on MacOSaiX, but I'm sure the process is largely the same in that app.

Step 3: Choose Your Image 

With your dimensions, choose what image you'd like to be the basis for your mosaic. Because of my "tall" dimensions, I had to be very selective on what image I could use. I ended up choosing a photo of Seattle's Space Needle.

The original image of the mosaics I created were taken with an iPhone 4, so don't think you need an image taken from some high-end SLR camera. The megapixel count and light sensitivity of most smartphone cameras will do just fine.

However, I do recommend using an image with some contrast. In my Space Needle mosaic, the area's of blue sky have images that are wholly different than the darker areas. If you use a low contrast image, your mosaic will lose that variance.

Step 4: Crop Your Image

I used iPhoto to crop my image. Here's how to do it:

  • Press 'Edit'.
  • Press 'Crop'
  • Choose 'Custom' from the drop-down.

  • Type your dimension numbers. They don't need units, as this is only producing a ratio. I put in 36 and 72, as those were my measurements in inches. Don't press 'Done' just yet.

  • Click on your image and move/scale the cropping area as necessary. When you got it just as you like, press 'Done'.

Now it's time to export your image. 

  • Go to File > Export.
  • JPEG Quality > Medium
  • Size > Full Size

Save to a folder. I recommend creating a new folder to store all the files we will be creating with this project. Call it "Mosaic Poster Adventure Time". The clerk at the print shop will know you mean business.

Step 5: Choose a Folder/Album/Event that will Comprise Your Mosaic

Now's the time to think what you want your mosaic to be comprised of. In my case, my base image was taken while traveling on the west coast for several months. I decided my mosaic would be comprised of images only from that trip.

You will be able to choose multiple folders/albums/events, so don't worry about the images you want to use all being in the same file locations. Again, MacOSaiX is a really great app.

Step 6: Generate Your Mosaic Image

Alright, you're all set, cowboy! Let's open MacOSaiX and witness some magic.

The first time you open the app, it should ask you what image you'd like to use to create the mosaic. Choose the image we exported from iPhoto.

Next, click Tiles Setup. Here, you can select how many tiles you want to span across and down. For my monolith poster, I chose 50 across by 100 down. As you change your settings, the app will tell you how many tiles will be in your image.

If you do some math, you can find out how big each tile will eventually be. Because my poster will be 36" wide, and I chose 50 tiles across, each tile will be 0.72 inches wide. From far away, your mosaic will look much sharper with more tiles, but one of the cooler parts of a mosaic is getting up close and seeing individual photos. 

I can't help you do your math, but try to find your happy medium.

After you've selected your tile settings, it's time to choose the images that will comprise your mosaic. An 'Image Sources' tab should appear on the right side of the app (if not, click View > Show Image Sources). In the 'Add New Source' drop-down, choose your folder or iPhoto album.

After pressing 'Save', your mosaic will begin generating. It's completely hypnotic to watch it come together. If you want to add more images (such as cover art from an iTunes playlist that you listened to while traveling), you can add more sources.

Depending on your image, this could take between a half hour or several hours. Go and file your taxes, Jimbo.

Step 7: Export Your Mosaic

Pretty cool, huh? It amazes me every time.

OK, let's export this beauty. Click File > Save As…

You're going to see a few options here. The most important one to me is the 'Fade' slider at the bottom left (to those in the know: this affects the opacity of the tiles). Mosaics using just your images aren't going to look exactly like your base image, but we can get it much closer by adjusting that slider. You can also change what your background will be. Play around and see which one works best. I found 'Clear' worked best for me.

Next, adjust the 'Sizes' fields to match what your end result will be. In the Print World, 300 DPI is the magic number to shoot for, but my image was too big and threw a caution sign to me, so I lowered it to 150 DPI. Try to get 300 DPI if you can, but if not, 150 DPI will work just fine.

Now, choose PNG. It's the best bang for buck in terms of quality and file size.

Press 'Save'. This might take a while, but afterwards, you'll be greeted with your  image file.

Step 8: Miller Time!

Seriously, if you've never done something like this before, just take a few minutes to stand back in awe. I was discussing this with a friend a couple weeks ago: what we've just made would not have been possible 15 years ago to the average citizen, and perhaps large companies as well.

Using just our personal computer, we have created something that an art department would have spent weeks creating and charging an enormous sum for. And how much have we spent so far? Other than our time, we've spent $0.00 CAD/US. Pretty damn cool. 

In the next post, I'll explain how to print, cut, and mount your poster.