如何使用Java Swing編寫骯髒的漸變彩繪邊框

Question

修訂：問題是繪製四邊的邊框，其中每一邊都以固定的基色開始，並在邊框的跨度上向內漸變爲白色。面臨的挑戰是讓邊界的交叉看起來無縫。要做到這一點，可以繪製邊界，然後使用三角形來「混合」角點。如果兩個平行邊界延伸邊界的全部長度（即矩形重疊），則如果在畫出Broder的矩形中沒有重疊，或者每個角的一個三角形足夠（如下所示），則每個角可以使用兩個三角形。

    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

，如果你不相交的長方形，而是使用多邊形（的GeneralPath）什麼？

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); 

這樣矩形不會重疊，而是你有不同環節之間很好的清晰的邊緣。

Answer 2

而不是創建和繪畫4個矩形，我將創建一個單一的Shape使用Area從一個外減去內部矩形代表你的邊界區域：

Area area = new Area(new Rectangle2D.Double(...)); 
Area inner = new Area(new Rectangle2D.Double(...)); 
area.subtract(inner); 

g2.setPaint(new GradientPaint(...)); 
g2.fill(area);