PI6 QuickTip #26: Shift Image for a Seamless Tile


Sometimes when you're trying to make a seamless tiling background, there are gaps or hard lines when the background is repeated. For example, in the border background shown below, a simple pattern is repeated twice.

border background pattern

I want to be sure that when this tiles as a background, there aren't any unseemly gaps. I've selected and cropped as close as I can to the leaves at the top and bottom of the border, but the shadows on the leaves make it difficult to crop too closely.

To solve this problem, choose Web, Shift Image. This command shifts the edges of an image to the center, and moves the center to the outside. By doing so, you can find places in the image that interfere with a seamless tile. 

When the Shift image dialog box opens, I shifted the Vertical offset only. Here I've shifted it by only 100 pixels, just enough to show an unseemly gap that will look odd in a tiled background border.

Shift Image vertically

Now that the image has been shifted, you can see the gap very clearly.

gap prevents seamless tile

Now you have a couple of options to fix this gap. You can clone from another area, make a selection from another location in the border and copy and paste it over the gap, or add an object. That's what I did here -- I simply added another object, a small snail, to cover the gap in the border. Note that I added a shadow to this object, so that it blends in with the rest of the border. 

gap closed up

Check out the border now, tiled across a page.

Here's the same situation. You find an image you'd really like to tile, but when you try to fill a page or a selection, there are hard edges where the image repeats itself. For example, this stained glass, courtesy of Spectrum Glass

non-tiling glass

When tiled, there are hard edges that mess up the tile. To remedy this, choose Web, Shift Image. Shift the image by one-third to one-half the number of pixels in height and width. You'll move the hard edges to the middle, where you can see them better.

shift image

Choose the Clone Paintbrush tool and set the brush to a very large size, like 50 or so, with a Soft edge of 50. Shift+Click to clone an area to the left of a line, then click on the line to hide it. Alternate Shift+Clicking on the right and left, above and below the hard lines, then clicking on the hard lines to cover them. You may have to Undo and try other areas, so that the swirls all blend together. Here's the finished result.

clone over seams

To test your shifted image, choose File, Preview in Browser, As Tiled Background. Take a good look at it, and if it needs more work, go back and clone some more. If it looks good, save the image. If you want to, you can add it to your EasyPalette's Fill Gallery after you save it. Simply right click on the Fill Gallery and choose Add Fill Thumbnail. Browse to the file you want to add, give it a name, and a thumbnail will be added to the Fill Gallery.

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