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Java how to draw and fill a Polygon which has holes

I am currently trying to draw and fill a Polygon which has a hole in it in Java. Normally this would not be a big problem, since I would draw the exterior ring and then draw the interior ring with the color of the background.
But the problem is, that the polygon is displayed above a image which should be "seen" through the hole.
I am writing the code in Java and am using JTS Topology Suite for my geometry data.
This is my current code, which just paints the border and fills the polygon with a color.
private void drawPolygon(com.vividsolutions.jts.geom.Polygon gpoly, Color color, Graphics2D g2d){
java.awt.Polygon poly = (java.awt.Polygon)gpoly;
for(Coordinate co : gpoly.getExteriorRing().getCoordinates() {
poly.addPoint(co.x, co.y);
}
g2d.setColor(col);
g2d.fill(poly);
g2d.setColor(Color.BLACK);
g2d.draw(poly);
}
Sadly java.awt.Polygon does not support Polygons with holes.

Use the Polygon as the basis for an Area (e.g. called polygonShape).
Create an Ellipse2D for the 'hole', then establish an Area for it (ellipseShape).
Use Area.subtract(Area) something like:
Area polygonWithHole = polygonShape.subtract(ellipseShape);

There are some ways to draw shapes or areas that are more complex than a simple polygon (another answer already mentioned Area).
Besides those, you could try to tessellate your final polygon. There are lots of algorithms to do this. For more complex shapes, the algorithms get a bit more complex as well. Basically, you're dividing your final shape into little polygons (usually triangles, but it also can be something else) and then draw those polygons.
You can take a look at your possibilities by searching for "Tessellation Algorithm", there are also some already implemented libraries for Java.

You can use java.awt.geom.Path2D to render a "compound shape" with a hole in it:
If you have java.awt.Shape objects defining the outside & inside edges of the shape, use append(shape, false) to add each shape.
If you have a set of path points for the outside edge and a set of path points for the inside edge, use lineTo() to add the first set of points - creating a closed loop by either ending with the same point you started with, or calling closePath() to automatically close the loop. Then use moveTo() to create a break before adding the inner set of points via more lineTo() calls.
In either case, you must create the path passing Path.WIND_NON_ZERO to the constructor - otherwise the hole won't be left unfilled.
See How to create shape with a hole? for a longer code example.

You could fill the polygon first, and then draw the holes on top, giving the illusion that it filled everything but the holes.

How to Draw line Graph having different colors in Single Line

I want to Make the Line Graph like Below Image :
I've had a look at some Stackoverflow questions such as How to Draw Line with Using Canvas, How To Draw Lines With Different Colors and so on. But I haven't been able to figure it how to do it myself.
Question :
I have an idea about what I could make with the AChartEngine Line Chart Graph. I'm not sure, how possible is it to create a line graph with the AChartEngine?
What are the alternatives to achieve the same result?
Any help would be highly appreciated.

That is not difficult, you need to create a radial gradient paint with the center in the middle of the curve. Then in colors[] you add as many colors as you want. For positions you can set to null, then the colors will be evenly distributed.
myPaint.setShader(new RadialGradient(
float x, float y,
float radius,
int[] colors,
float[] positions,
Shader.TileMode tile));
Also you should apply this only when the path is formed; you will need to get path bounds with
RectF bounds = new RectF();
myPath.computeBounds(bounds, true);
Now you can easily find center and radius.

You can add several series of data, each one having a separate color.

drawing pacman in Java

Hello for a school exercise i need to create a game and i decided to create Pacman. Everything goes well but one thing i can't accomplish is to draw a pacman dude and his ghosts.. i made and oval but what now? i want the pacman mouth also to open and close as it moves. can someone help drawing this?
below what i have till now:
package h04PacMan;
import java.awt.*;
public class DrawPacMan {
public void drawPacMan(Graphics g, int x, int y, Color color) {
g.setColor(color); // set color
g.fillOval(x, y, 50, 50); // paint
g.setColor(Color.black);
g.drawOval(x, y, 50, 50); // outline
// mouth?
}
public void drawGhost(Graphics g, int x, int y, Color color) {
g.setColor(color); // color
// here goes shape
}
}

Instead of using drawOval and fillOval, you should have a look at drawArc and fillArc.
See java.awt.Graphics.
Concerning the animation of the mouth: Given that pacman is constantly moving, you could combine pacman's position with a sine function to get a nice and smooth mouth movement, something like this:
angle = 20 * (Math.sin((x + y)*2*Math.PI/50) + 1); # alt. betw. 0 and 40
g.fillArc(x, y, 50, 50, angle/2, 360-angle);
This way, Pacman's mouth will automatically do one open-close-cycle as he moves a distance of his own size through the maze. (You may have to tweak the numbers a bit to fit your setup.)
Of course, you will still need a thread to run the game as a whole, but the animation of Pacman's mouth can be done this way, too, without extra threads.

So there are a couple of things going on here that you will need to address.
1. Drawing Characters
I'll only address drawing Pacman here.
Thinking about the Pacman game, Pacman's character has two states -- mouth closed, and mouth opened (in each cardinal direction!). This will be important for when we animate Pacman in a moment, so first, lets establish our pacman shape by using the fillArc method from the Graphics library.
Example of Mouth-Open Pacman:
g.setColor(Color.yellow);
g.fillArc(0,0,150,150,30,300);
This will create pacman in the top-left corner of your window, with pacman's mouth facing to the right of the screen. The last two paramters of the fillArc method control this opening -- the 5th parameter is the starting angle, and the sixth parameter is the angle of the full arc. You may infer from this that the start angle 0 is the horizontal line going from the center of the arc to the right of the screen. Also remember from mathematics that a full circle is 360 degrees.
Using this information, try drawing mouth-opened Pacman facing up, down and left. After you do that, fill the entire arc to draw Pacman with his mouth closed. Also consider other methods in the Graphics library you can use to draw your ghosts!
2. Animating Pacman
For this task you will probably want to implement some sort of Thread structure to animate Pacman, which gets quite a bit more complicated than what you've demonstrated here. Since we don't know your program specifications, and you also haven't demonstrated any code relating to the animation yet, I'm hesitant to lay this out any further. However, I will direct you to some links on the matter:
For a general overview, check out Java Tutorials - Concurrency.
If you're using Swing for this project, you may want to use SwingWorker for your threads.

I'd recommend taking advantage Area/Path2D API.
Have a look at Graphics 2D
You can have a look at the sample code in this answer for an example

Java: line-stroke with filled shape

This is not really important, but it was bothering me for a little while.
Problem description:
Given: a line (Line2D)
Wanted: drawing the line as a wedge (Filled GeneralPath)
Surely this can be done by creating the wedge as General Path and then filling it by the Graphics (my solution).
My first approach would have been a wedge-stroked line, because I didn't want to change the line object for some reason, also I just wanted to draw the line object and not think about it any more.
Creating the wedge-stroke was no problem (Some calculations and then creating the General Path) - but I was not able to fill it (easily)
Apparently it seems the fill of Graphics2D only fills the shape it gets - and does not handle the filling of the stroke (that behavior makes sense if one thinks about it).
Question: Is there any way to fill a shape of a Stroke (filling a shape - more specifically: a GeneralPath - somehow before drawing it)?

May be BasicStroke.public Shape createStrokedShape(Shape s) can help if you pass the Line2D there?

Once you use createStrokedShape(), note that draw() "strokes the outline of a Shape," while fill() "fills the interior of a Shape."

import java.awt.*;
public static Shape strokeToShape(Shape path, float strokeWidth)
return new BasicStroke(strokeWidth).createStrokedShape(path);
}
You may also specify cap and join parameters of BasicStroke

Curved sides of triangle path?

I am drawing a triangle on a Canvas, something like:
canvas.moveTo(0, 30);
canvas.lineTo(40, 0);
canvas.lineTo(40, 40);
canvas.lineTo(40, 40);
canvas.lineTo(0, 30);
And get proper triangle on my Canvas. But I need to curve the sides a little and fill that path with specific color. What is the easiest way to do this? Drawing arcs? But how to fill the object?
Thanks!

EDIT: I noticed you were using android's canvas, not HTML Canvas, sorry. The concept is exactly the same except you'll call quadTo() instead of quadraticCurveTo(), so my example should still get you going.
Also on android you use canvas.drawPath(path, paint) and pass in a paint that has its Paint.style set to FILL_AND_STROKE.
You will want to construct the path, fill() it, then stroke() it in order to get both a filled path with the stroke outline.
To get that particular shape, the easiest way is to draw two quadratic curves. A quadratic curve first needs a control point x,y then the end point x,y. The control point for both curves should be around the middle of your desired triangle. Here is an example:
ctx.fillStyle = "lightgray";
ctx.moveTo(0, 100);
ctx.quadraticCurveTo(50, 50, 50, 0);
ctx.quadraticCurveTo(50, 50, 100, 100);
ctx.lineTo(0, 100);
ctx.fill();
ctx.stroke();
Here is that example live for you.