Design an image - don't let the design go all the way to the edge of your canvas. Make your image square. Your image can be a print or painting that you scan into your computer, or something that you create using your computer. Open it in Photoshop. Then, to practice and get comfortable with this process, RESIZE your image to something that is fairly quick to handle - say, 500 pixels by 500 pixels at 72 DPI/PPI. You can get serious later with higher resolution.
|I've made this with a lot of Contrasting Colours so that you can see it better, even though the design doesn't make a lot of visual sense. This image is 500 x 500 pixels.|
Now, open a new blank canvas that is 500 x 500 pixels. Then go to your image canvas, click on the Select Menu, and click "All".
|This selects your entire canvas quickly and accurately.|
Go to Edit Menu, and click on Copy. Move to your blank canvas, and click Edit, then Paste.
Now you have two identical screens, one with your original image, and one with the new canvas and your image layered on top.
To begin your Half-Brick Repeat, you must double the width of your "New" canvas. You do this by going from the Image Menu - select Resize, then Canvas Size. You'll see a screen that shows you the current size of your image (500 x 500 pixels), and a section labeled "New Size". In that section, make the WIDTH of the canvas exactly double, or 1000 pixels. Keep the height the same as your original image. Before you click OK, select the anchor on either the right or the left so that you get a full 500 pixels added to one side of your existing canvas, not 250 on each side.
|See the Anchor arrows - this will make sure that the additional width is added to one side.|
Duplicate this layer. You can name it or not - I usually don't because I'm moving too fast!
To "drop" the image by 1/2, go to the Filter menu, choose Other, then "Offset".
On the Offset Screen, enter the original width of your canvas in the Horizontal block, and half that value in the Vertical block. This will drop your image by half.
Now your image looks like this:
|Flatten the layer after Offsetting it.|
I filled mine in with Doodles and such, just to show you how to fill it out...
After you've filled in your design, be sure to flatten it if necessary, then Select All again, and move to the edit menu and select "Define Pattern From Selection". Name the pattern the same name as your new file.
Open a new canvas at least twice as large as this pattern - 2000 x 2000 pixels. This will allow you to see your repeat better. Select -> All, then Edit-> Fill Selection, using your newly named pattern. And this is what it looks like!
Now you can adjust your "additions" to make sure they are pleasing to the eye when filling a large expanse, and don't create an obvious line (like mine did up the middle). Once you do this a couple of times, it will be so easy. Now, get to designing!