使用BufferedImage进行渐变色操做

序

本文主要简述一下如何使用BufferedImage进行渐变色操做。

GradientPaint

java/awt/GradientPaint.java

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

这个是生成渐变色的关键类，固然也有其余的渐变类，好比
java/awt/LinearGradientPaint.java

实例

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); //从左上到右下渐变;

        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画一个渐变色的矩形，而后将原图使用必定透明度覆盖上去，这样就看出渐变。
不足以后的话，就是渐变颜色会偏淡。