由透明png精灵制作多边形的算法 [英] Algorithm to make a polygon from transparent png sprite

问题描述

说，我有一个游戏对象的子画面，它是具有透明度的png图像.

Say, I have a sprite of a game object which is a png image with transparency.

我想从此图像创建一个包含我的游戏对象的多边形.

I want to create a polygon from this image which will contain my game object.

我很确定有一种现有的算法，但是我还没有找到任何算法.

I am pretty sure there is an existing algorithm for it, but I haven't found any.

我希望这样:

public static Polygon getPolygon(BufferedImage sprite)
{
    // get coordinates of all points for polygon
    return polygon;
}

推荐答案

请参阅此问题.它会很慢，但要取决于您想要的精度(第二个答案更草率，但要快一些).在另一个问题上从getOutline()获得Area后，请尝试使用此代码(未经测试):

See this question. It will be slow, but it depends on how accurate you want it (second answer is sloppier, but a bit faster). After you get the Area from getOutline() on the other question, try using this code (untested):

public static Polygon getPolygonOutline(BufferedImage image) {
    Area a  = getOutline(image, new Color(0, 0, 0, 0), false, 10); // 10 or whatever color tolerance you want
    Polygon p = new Polygon();
    FlatteningPathIterator fpi = new FlatteningPathIterator(a.getPathIterator(null), 0.1); // 0.1 or how sloppy you want it
    double[] pts = new double[6];
    while (!fpi.isDone()) {
        switch (fpi.currentSegment(pts)) {
        case FlatteningPathIterator.SEG_MOVETO:
        case FlatteningPathIterator.SEG_LINETO:
            p.addPoint((int) pts[0], (int) pts[1]);
            break;
        }
        fpi.next();
    }
    return p;
}

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