java - 如何在 Java 中淡化图像的边缘？ (给出的例子)

Question

我目前正在进行一个项目，在该项目中，我必须在按下 JButton 时对猫的图片进行灰度化、蓝色滤镜、红色滤镜、绿色滤镜以及淡化边缘。对图片进行灰度和颜色过滤很容易，但我似乎不知道如何将图像的边缘淡化为黑色。

我的意思是，我有一张我需要更改的猫的照片:

我需要将其更改为类似这样的内容:

    import javax.imageio.ImageIO;
    import javax.swing.JButton;
    import javax.swing.JPanel;
    import javax.swing.JFrame;
    import javax.swing.JLabel;
    import javax.swing.ImageIcon;
    import java.awt.image.BufferedImage;
    import java.io.File;
    import java.io.IOException; 

    public class GUIKittenPicJC {
        public static class KittenChanger extends JPanel {
                BufferedImage img = null;
                File Kitten = null;
                ImageIcon imagetransformed = null;
                JButton grayscale = new JButton("Grayscale Image");
                JButton rgbB = new JButton("Blue filter this image");
                JButton rgbR = new JButton("Red filter this image");
                JButton rgbG = new JButton("Green filter this image");
                JButton fader = new JButton("Fade this image");
                {
                try
                {
                    Kitten = new File("C:\\Users\\Jarrod\\Desktop\\Lab 3\\Lab 3\\kitten.bmp");
                    img = ImageIO.read(Kitten);
                }
                catch(IOException e)
                {
                  System.out.println(e);
                }
            ImageIcon image = new ImageIcon(img);
            JLabel imageLabel = new JLabel(image);
            add(imageLabel);
            grayscale.addActionListener(e->{
                       imagetransformed = new ImageIcon(Grayscale(img));
                       imageLabel.setIcon(imagetransformed);
                       imgReset();
                    });
            rgbB.addActionListener(e->{
                   imagetransformed = new ImageIcon(Bluify(img));
                   imageLabel.setIcon(imagetransformed);
                   imgReset();
                });
            rgbG.addActionListener(e->{
                   imagetransformed = new ImageIcon(Greenify(img));
                   imageLabel.setIcon(imagetransformed);
                   imgReset();
                });
            rgbR.addActionListener(e->{
                   imagetransformed = new ImageIcon(Redify(img));
                   imageLabel.setIcon(imagetransformed);
                   imgReset();
                });
                        add(grayscale);
                        add(rgbB);
                        add(rgbG);
                        add(rgbR);
                }
                private void imgReset() {
                    try {
                            img = ImageIO.read(Kitten);
                        } 
                    catch (IOException e1)
                        {
                            e1.printStackTrace();
                        }
                }

        }
        public static void main(String[] args)
        {
           createGUI();
          }
            private static void createGUI() {


                JFrame frame = new JFrame("Kitten Changer");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                KittenChanger newContentPane = new KittenChanger();
                newContentPane.setOpaque(true);
                frame.setContentPane(newContentPane);
                frame.setSize(400, 500);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

//Grayscale and rgb filter methods follow, not important to question
}

我如何为此类过滤器创建一个方法并将其正确应用于像其他按钮一样的按钮？

Answer 1

您必须单独编辑每个像素。该解决方案的主要思想是，您拥有图像的中心，并且每个像素都会根据到中心的距离而变化。

更简单地说，远离中心的像素将变得更暗。

您的代码如下所示:

BufferedImage cat; //assuming it is assigned
for(int i = 0; i < cat.getWidth(); i++) { // i is the x coord
    for(int j = 0; j < cat.getHeight(); j++) { // j is the y coord
        int color = cat.getRGB(i, j);
        int r = (color >> 16) & 0xff; //extract red value
        int g = (color >> 8) & 0xff;
        int b = color & 0xff;
        double scale = 0.75; /**** Change this to change the resulting effect ****/
        //pixel's distance from center
        double dist = Math.sqrt( Math.pow(i - cat.getWidth()/2, 2) + Math.pow(j - cat.getHeight()/2, 2) );
        r = (int) Math.max(0, r - dist*scale); //r - dist*scale makes px darker
        g = (int) Math.max(0, g - dist*scale); //Math.max makes sure r is always >= 0
        b = (int) Math.max(0, b - dist*scale);
        int newRGB = (r << 16) + (g << 8) + b; //convert r,g,b to single int
        cat.setRGB(i, j, newRGB); //finally, update rgb value
    }

}

而且，当我运行这段代码时:

请记住，您始终可以通过更改上面代码中的 scale 变量来更改效果。