Why are Polygons misshaped when using Vector coordinates in a Java Applet?

Question

I have a completely graphed out blueprint of X, Y coordinates of 8 different multi-pointed shapes on paper. I put these coordinates into an array such as..

Polygon shape1;    
int[] shapeOneX = {1,2,3,4,5,6,7,8,9};
int[] shapeOneY = {1,2,3,4,5,6,7,8,9};
shape1 = new Polygon {shapeOneX, shapeOneY, shapeOneX.length};

These coordinates are fake, and not my actual ones but on paper, these coordinates would follow the rules completely on how you would expect vector graphing to look like. When I load this into a Java Applet, the shape does not follow these exact coordinates. They're sometimes close, but not exact, and I need precision for my project.

Does anyone know why, or if there is a different formula you need to use on the coordinates to have it look the same in a java applet? If need more info, let me know.

I understand that starting coordinates for java applet start at the top left 0,0 then expand from there. I guess my questioning is,I have the understanding that "vector" cords start at 0,0 as a Mid point. I don't know much about graphing. So... my shapes are being created from a vector style, but being "placed" into an applet which has a 0,0 top left origin. Which is fine, I have the tools to adjust them where I need to put them. I just can't get them to create the shape I actually graph on paper. Do I need to graph on paper from a 0,0 top left origin and only create positive X, Y variables?

Another Edit-- I've noticed that when it draws onto the applet, it draws it almost mirrored as well. In other words, (x) goes right, (-x) goes left. That's normal. But (y) goes DOWN, and (-y) goes UP.. That doesn't seem normal HMM.. Confused.

Final Edit(probably) -- Well I was right about the Y axis being mirrored. Why? I don't know. But it has allowed for me to redesign some coordinates. I am currently under the impression that line borders were so thick that connected each vertex, that they reformed the shapes into a blob of junk. Because of the overlapping borders. It was hard to see where each vertex actually truly was. I also had to increase the values of my (x,y) coordinates in order to compensate for the size difference. Which I have probably near 100 or so different (x,y) combinations that I will need to re-do because of this... I really wish there was an easier answer. I am open to any and all suggestions, meanwhile I will plug away at remapping this. Thanks everyone who has, or continues to contribute.

For Example.. This first was the orignal coordinates:

       int[] wallX = { -2,-2,-1,-1, 2, 2 };
       int[] wallY = { -1, 3, 3, 0, 0,-1 };

And then the new WORKING coordinates I found to work are:

    int[] wallOneX = { -2,-2, 1, 1, 10, 10 };
    int[] wallOneY = {  4,-8,-8, 1, 1,  4  };

So thats the difference of numbers needed to create the same shape from paper, into the java applet. I don't really see a pattern or anything to recreate it for all my other ones. So I don't know.

Answer 1

You need to scale your coordinates based on the height and width of your jpanel or canvas object on which you are painting the polygon. use getHeight() and getWidth() to get the dimensions. Also, the origin is in the upper right corner of the jpanel or canvass, so you either need to use addition/subtraction to shift the scaled coordinates, or you need to use the affine transform to get the polygon where you want it to go.

Sometimes it helps to start with working examples. You might try this approach or this approach. Here is a third approach already in an applet.