My bar section is 5x3 pixels, and the background image is 199x16 pixels (which is 4 width off from what I should have done. Oh well, it's just a demo). My demo simply adds a bar section every 5 points up and down, using a different picture number.
RPG Maker does pictures assuming that 0,0 is the center, which is retarded and wrong, but you'll have to work around that. To put something in the upper left, you put it at (width/2, height/2) generally, so the background went at 100,10 (to add a 2-pixel buffer at the top.. and a 1-pixel buffer on the left).
This means that since the first bar (5 points towards good) would be at 100, 1 on the image, it's at 101, 3 with the buffers.
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Now, I have that 5x3 bar segement to add. The center is really easy to find:
It's at 2,1 (0,0 is the upper left by most standards). To get the upper left to go to 101,3, I need to add that 2,1 to that, making the first segment go at 103, 4.
Every other segement is a piece of cake from here - Just keep adding 5 to the x value, since that's the width of the bar and we don't want to overlap them.
Basically, the answer is math. If you have a background image ready, I'll calculate out the whole deal for you if you want - RPG Maker has a really, really strange picture system. Just make sure that the height/width is an odd number to save me some calculating time.
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Truthfully, the last bars on both sides will overlap the background since I was stupid and used the wrong image size. Oh well, it was late.
MATH THAT I SHOULD HAVE DONE:
Since I wanted 5 pixels for every 5 points (with a max of 100), I needed a 100 pixel bar for good, and a 100 pixel bar for evil. I used a 1-pixel border and a 1-pixel center line, making the whole bar supposed to be 203. (Do yourself a favor and stick to odd-numbered pixels. Much easier to find the center.)
Beyond that, the rest of the image is the words GOOD and EVIL, so the height is just based off of that. Now that I actually am not up at midnight working on the images, I can look back and say that I made my work harder by using 16 as a height and not 17. It's still fine though.
Using that system, the center is at 101,8 (though I'd add buffers, so I'd put the image at 103,10) and the first bar would have gone at 105, 6. From there, it would have continued normally, just adding 5 to the x value.
The math is really simple, yet difficult to explain in words.