使用BufferedImage進行漸變色操做

序

本文主要簡述一下如何使用BufferedImage進行漸變色操做。

GradientPaint

java/awt/GradientPaint.java

public class GradientPaint implements Paint {
    Point2D.Float p1;
    Point2D.Float p2;
    Color color1;
    Color color2;
    boolean cyclic;
   //......   
}

這個是生成漸變色的關鍵類，固然也有其餘的漸變類，好比
java/awt/LinearGradientPaint.java

實例

public static BufferedImage drawGradient(BufferedImage srcImg,
                                             int startX, int startY,
                                             int endX, int endY,
                                             Color colorFrom, Color colorTo,
                                             float opacity) {
        BufferedImage dstImg = new BufferedImage(srcImg.getWidth(), srcImg.getHeight(), BufferedImage.TYPE_INT_RGB);
        GradientPaint grad = new GradientPaint(startX, startY, colorFrom, endX, endY, colorTo); //從左上到右下漸變;

        Graphics2D g2 = (Graphics2D) dstImg.getGraphics();
        g2.setPaint(grad);
        g2.fillRect(startX, startY, endX, endY);

        g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, opacity));
        g2.drawImage(srcImg, 0, 0, srcImg.getWidth(), srcImg.getHeight(), null);
        g2.dispose();

        return dstImg;
    }

原理就是先使用GradientPaint畫一個漸變色的矩形，而後將原圖使用必定透明度覆蓋上去，這樣就看出漸變。
不足以後的話，就是漸變顏色會偏淡。