Here's a way to make continuous patterns using just about any paint-type program. I use Aldus SuperPaint 3.0 to make most of my ppat patterns.
Step 1
Open your paint program and draw a square (I'll draw a black square this time) that is 128x128 pixels. You should use 64x64 or smaller if you think you'll want to edit these ppats in ResEdit later.
 
Step 2
Use your paint program's masking tool to make a mask on the right side of the square. Your program may have a different name for "mask." What a mask does is protect the "masked" area of the picture from being changed while the mask is active.
 
The mask should start just outside the square and extend to the right.
 
Step 3
Add to the mask on the bottom of the mask. SuperPaint uses the "Add to mask" command. Once again, your program may use different terms.
 
Your screen should look something like this:
 
Step 4
This step will be different for every pattern. Paint whatever you want in the area of the square. You don't need to be to careful to stay inside the square, we'll fix the messiness later! I will simply use several small graphic images of myself to fill the area of the square. You can paint anything or import other graphics into the pattern.
 
Step 5
Now it's time to clean this pattern up into a 128x128 square. Select all of the graphic that "hangs over" the left edge of the original graphic square.
 
Step 5a
Change the copy mode of the selected area to "Transparent background." Your program may have different commands to do this.
 
Step 5b
Move the selected area to the right side of the square, up against the mask on that side. Hold down the shift key while moving the area so that you do not have any verticle movement. Your pattern-in-the-works should look something like the below screen shot.
 
Steps 6, 6a, 6b
Do the same series of manipulations with the part that is "hanging over" the top of the pattern.
 
 
 
Step 7
You're almost there! Turn off or delete the mask around the pattern.
 
Step 8
Make sure that your pattern is still 128x128 (sometimes you get a little too much / not enough of the "excess" pattern when you're moving things around). Copy the pattern to paste into the scrapbook or into a ppat program (I like Desktop Textures). If everything's gone OK you should have a fairly "continuous" looking pattern.
 
I hope that this tip has been helpful to some of you out there. If there is enough interest, I may make and distribute a few more of my ppat creation tips. Congradulations if you made it this far!
