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Making a Seamless Tile

Although there are a number of tiles of coins available on the net and on clipart CDs, they all seem to be of US money. So while we still have sterling let's make a tile of UK coinage. As ever, there are a number of different ways of doing this; we'll use the Cloning effect here.

First you need an image. You can take a picture with a digital camera if you have one, but you'll need to take care with flash reflections. A better way is to use a flatbed scanner. Place some coins on the bed (taking care not to scratch the surface) with some banknotes as background, and scan at low resolution (90dpi). If you want to use the tile for high-quality work use a higher resolution, but 90dpi is fine for screen use. Save as a TIFF. You should end up with something like this:

Money, half-size

Now load the image into Photodesk and follow these steps:

• First we define an area to use as the basis for the tile. Click on the Scissors, then the Crop/extend icon (a rectangle with a cutaway).
• Drag out a rectangle on your image. Make it 256x256 pixels - you can enter this into the W and H writeable icons in the Crop/extend window if you have trouble getting it right with the mouse. You can use any size, but most tiles are defined as square with sides of a power of 2. With this particular image, 256x256 is about right - you can fit a number of different coins in the tile, and the repeat won't be too obvious.

  

  Selecting part of the image

• Move the rectangle around (click and drag anywhere inside it) until you've enclosed a nice selection of coins.
• Now click on the Tick to crop the image to your selection.
• Save this under a different filename (you'll need the original again). Photoshop format is best.
• Open the Offset image window (type Ctrl-O or select the menu option Photodesk>Image>Offset...).
• Select both the Horizontal:Bisect and Vertical:Bisect icons, then click on Offset.
• You should see something like this:

  

  Offsetting the image

• What this has done is put the parts of the image that don't match into the middle, where they can be seen and repaired. You can now tidy it up using the Clone effect.
• First reload your original scanned image, and arrange the screen so you can see both this and your newly offset tile.
• Click on the Palette icon to go back to painting mode, and choose the Airbrush tool. Select a small sized brush.
• Now click on FX and select the Cloning effect from the menu.
• What you need to do is match up a coin on both images, then select this as your source. We'll start with the half-visible 5p in the upper right quadrant. Click on Sample, then find an easily-identified highlight. Click on this in the original scanned image; a cross should appear.
• Now click very carefully on the exact same point in your tile. You may find it helpful to work at x2 or x4 magnification, and to use the crosshair pointer (in the Tool pointers section of the Preferences... dialogue, on the iconbar menu).
• You should now be painting with the original coin. Paint carefully over the incomplete parts - don't be afraid to paint too much, as you can always repair it with the Adjust button. Here's a screenshot of this process, showing the source cross in the original image and the half-completed 5p in the tile.

  

  Painting in the missing bits

• Now carry on repairing the other joins in a similar manner. Use a smaller brush if necessary for fine work.
• If you find this process too difficult, you can just pick any coin in the original image and clone it over the joins. I did this with a £1 coin in the centre. Remember not to change the outside edges of the tile, which we know match up.
• When you've finished, check everything matches up by offsetting the image again (there should be no visible joins), fix and save. You should get something like this:

  

  The tile

• Test by saving as a sprite and trying it out as your desktop backdrop, or filling an empty canvas in Photodesk: Clone your tile (with Wrap around source selected) using Magic Wand:Whole image.

Notes

• Photodesk confusingly uses the word "texture" for both tileable and non-tileable images (for example, the Texture application does not produce tileable images, a major flaw in my view). I prefer the word "tile" for repeatable, arbitrarily-sized coloured images, and reserve "texture" for greyscale 128x128 images used for embossing and brush effects.