如何使用Java Swing编写肮脏的渐变绘制边框

Question

修订:问题是绘制一个四边形边框,每边开始时有一个坚实的基色,并在边框的跨度上向内渐变为白色.挑战在于使边界的交叉看起来无缝.要实现这一点,可以绘制边框,然后使用三角形来"混合"角落.如果在绘制粗体的矩形中没有重叠,则每个角可以使用两个三角形,或者如果两个平行的边界边延伸边界的整个长度(即矩形重叠),则每个角的一个三角形就足够了(如下所示).

    private static final int GRADIENT_LENGTH = 29;
    private static final int BAR_LENGTH = 25;
    public static void paintGradientBorder(Graphics g, Color borderColor) {


    Graphics2D g2 = (Graphics2D) g.create();

    GradientPaint gradientColorWest = new GradientPaint(0, 0, borderColor,
            GRADIENT_LENGTH, 0, Color.WHITE);
    GradientPaint gradientColorEast = new GradientPaint(WINDOW_WIDTH - GRADIENT_LENGTH,
            0, Color.WHITE, WINDOW_WIDTH, 0, borderColor);
    GradientPaint gradientColorNorth= new GradientPaint(0, 0, borderColor, 0,
            GRADIENT_LENGTH, Color.WHITE);
    GradientPaint gradientColorSouth = new GradientPaint(0, WINDOW_HEIGHT - GRADIENT_LENGTH,
            Color.WHITE,0, WINDOW_HEIGHT, borderColor);

    //south bar
    g2.setPaint(gradientColorSouth);
    g2.fillRect(0, WINDOW_HEIGHT - BAR_LENGTH, WINDOW_WIDTH, BAR_LENGTH);
    //north bar
    g2.setPaint(gradientColorNorth);
    g2.fillRect(0, 0, WINDOW_WIDTH, BAR_LENGTH);
    //west bar
    g2.setPaint(gradientColorWest);
    g2.fillRect(0, BAR_LENGTH, BAR_LENGTH, WINDOW_HEIGHT - BAR_LENGTH * 2);
    //east bar
    g2.setPaint(gradientColorEast);
    g2.fillRect(WINDOW_WIDTH - BAR_LENGTH, BAR_LENGTH, WINDOW_WIDTH, WINDOW_HEIGHT - BAR_LENGTH * 2);

    //NORTH WEST CORNER
    //left triangle
    Polygon p = new Polygon();        
    p.addPoint(0, 0);
    p.addPoint(BAR_LENGTH, BAR_LENGTH);
    p.addPoint(0, BAR_LENGTH);
    g2.setPaint(gradientColorWest);
    g2.fillPolygon(p);        
    //NORTH EAST CORNER
    //right triangle
    p.reset();
    p.addPoint(WINDOW_WIDTH, 0);
    p.addPoint(WINDOW_WIDTH - BAR_LENGTH, BAR_LENGTH);
    p.addPoint(WINDOW_WIDTH, BAR_LENGTH);
    g2.setPaint(gradientColorEast);
    g2.fillPolygon(p);
    //SOUTH WEST CORNER
    //left triangle
    p.reset();
    p.addPoint(0, WINDOW_HEIGHT);
    p.addPoint(0,WINDOW_HEIGHT - BAR_LENGTH);
    p.addPoint(BAR_LENGTH, WINDOW_HEIGHT - BAR_LENGTH);
    g2.setPaint(gradientColorWest);
    g2.fillPolygon(p);
    //SOUTH EAST CORNER
    //right triangle
    p.reset();
    p.addPoint(WINDOW_WIDTH, WINDOW_HEIGHT);
    p.addPoint(WINDOW_WIDTH, WINDOW_HEIGHT - BAR_LENGTH);
    p.addPoint(WINDOW_WIDTH - BAR_LENGTH, WINDOW_HEIGHT - BAR_LENGTH);
    g2.setPaint(gradientColorEast);
    g2.fillPolygon(p);

    g2.dispose();
}



    

Answer 1

如果不与矩形相交但是使用多边形(GeneralPath),该怎么办？

GeneralPath topBox = new GeneralPath();
topBox.moveTo(0, 0);
// upper right
topBox.lineTo(width, 0);
// lower right; move diagonally down and to the left as in a picture frame
topBox.lineTo(width - (insetX / 2), 0 + (insetY / 2));
// lower left
topBox.lineTo((insetX / 2), 0 + (insetY / 2));
topBox.closePath();
g2.fill(topBox);

这样矩形就不会重叠,相反,你会在不同的部分之间有清晰的边缘.