In making this poster, I'm using a utility called The Rastabator, which has a neat feature of being able to blow up almost any digital image to whatever size you see fit. So starting at the beginning I had decide just how big I wanted to make this picture.

In theory, I could plaster a rasterbated image over the entire width of one wall of my home office (2.4m wide). However, I decided to start smaller and create an image that would fit over the window of the door to my office. This would then be somewhat similar to the lighting panel used by the props guys at the BBC and it would give the illusion of my home office being "bigger on the inside".

The window is about 545mm wide by 920mm high (a ratio of 1:1.695), clearly the console room image I had would need cropping. That image is 860px wide by 600px high, so using the same ratio I would need to crop the image to 354px wide by 600px high.

Next I needed to fight a limitation of the Rasterbator software. When enlarging an image, you can only work in whole sheets of paper. This means using standard A4 paper I would need to print out 12 sheets (3x4) giving me a poster that was 630mm wide by 1070mm high. That's great as it would cover my window but I would then have to chop 90mm of the side and 150mm off the bottom to make it fit my window. That's a lot of wasted space, not to mention the wasted ink.

Furthermore, the rasterbator software "assumes" you can print up borderless printouts. By this I mean that your printouts can go all the way up to the edge of the paper, rather than having to leave a little gap around the outside.

Working on the idea that my printer could happily cope with a size of 200mm wide by 250mm high, I fed these numbers into the tool and found that I could have a printout that was 600mm wide by 1000mm high on 12 sheets of paper. Closer but not close enough for my liking as there would still be over 50mm of printed image to throw away down the entire length of the side and 80mm to throw away across the bottom. I would end up losing some of nice parts of the image too, so more cunning steps needed to be taken.

My plan was to add in a white border to my cropped image, which would be the same size as the bit I was going to chop off. Since I was forced to use 12 A4 sheets and would be throwing away the edges anyway, I figured it wasn't too much of an environmental impact. Besides, throwing away unprinted edges it always preferable to stuff that you'd just printed on. So, how to calculate the size of the white border? I've decided the best way to explain it to you is to use ratios (as I've used above). So lets start with the border along the side of the image

My window is 545mm wide, the print out is 600mm wide. This is a ratio of 1:1009. Applying that ratio to the cropped image, the new width should be 354px * 1.009 = 390px. So I added a 36px border to one side of the image. Applying the same rules to the height, I added a 51px border to the bottom of the image. This explains why the image on the right of this text has an extra white border. As you can see from the whitespace, this would be quite a lot of ink to waste.

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