In: Categories » Computers and technology » Flash » Drawing an Ellipse using ActionScript
| Create a custom MovieClip.drawEllipse( ) method using the Drawing API and invoke it on a movie clip. You can create a method of the MovieClip class to draw an ellipse that is very similar to the drawCircle( ) method. In fact, the drawCircle( ) method is merely a degenerate version of drawEllipse( ), in which the radii in the x and y directions are the same. The custom drawEllipse( ) method accepts four parameters: xRadius yRadius x y MovieClip.prototype.drawEllipse = function (xRadius, yRadius, x, y) {
var angleDelta = Math.PI / 4;
// While the circle has only one distance to the control point for each segment,
// the ellipse has two distances: one that corresponds to xRadius and another that
// corresponds to yRadius.
var xCtrlDist = xRadius/Math.cos(angleDelta/2);
var yCtrlDist = yRadius/Math.cos(angleDelta/2);
var rx, ry, ax, ay;
this.moveTo(x + xRadius, y);
for (var i = 0; i < 8; i++) {
angle += angleDelta;
rx = x + Math.cos(angle-(angleDelta/2))*(xCtrlDist);
ry = y + Math.sin(angle-(angleDelta/2))*(yCtrlDist);
ax = x + Math.cos(angle)*xRadius;
ay = y + Math.sin(angle)*yRadius;
this.curveTo(rx, ry, ax, ay);
}
}
Once you have defined and included the drawEllipse( ) method in your Flash document, you can draw an ellipse rather easily. Use the drawEllipse( ) method the same way you used the drawCircle( ) method but provide both x and y radii instead of just a single radius. Remember that you still need to define the line style before you call the drawEllipse( ) method. // Create an ellipse with minor and major axes of 100 and 200, respectively.
this.createEmptyMovieClip("ellipse", 1);
ellipse.lineStyle(1, 0x000000, 100); // Use a one-pixel, black, solid border
ellipse.drawEllipse(100, 200);
Having defined drawEllipse( ), we can rewrite the drawCircle( ) method, as follows: MovieClip.prototype.drawCircle = function (radius, x, y) {
// Call drawEllipse( ) with the same radius for both x and y.
this.drawEllipse (radius, radius, x, y);
}
|
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