在java中将像素的alpha通道设置为零

Question

我想做一个小程序，允许您更改图像选定像素的 Alpha 通道。想想 Photoshop 上的橡皮擦工具。因此，我让程序在图像上绘制颜色，并尝试使用 setRGB(0x00000000,0x00000000,0x00000000) 将像素设置为 alpha 0；没有骰子，只是涂黑。

我还尝试画一个蓝色椭圆形（效果很好），所以我知道我的鼠标侦听器正在工作。 （代码中已注释掉）

现在我正在获取该图像的光栅并尝试使用 setPixels() 或 setRect() 修改 Alpha 通道，但我似乎无法让它发挥作用。我想我的问题是你必须通过的数组。我假设它是一个 10 x 10 像素数组和 4 个通道，因此数组的长度必须为 400。

这是我第一次尝试这个，所以我的代码有点丑陋，有很多注释掉，因为我已经尝试了大约一百万种方法这样做；但就是这样。

感谢您提前提供的任何帮助。

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class MyFrame extends JFrame implements MouseListener,
    MouseMotionListener {

    BufferedImage myImage = new BufferedImage(300, 300,
        BufferedImage.TYPE_INT_ARGB);
    BufferedImage blankImage = new BufferedImage(10, 10,
        BufferedImage.TYPE_INT_ARGB);
    File myPNG = new File("output.png");
    MyPanel mp = new MyPanel();
    File tempPNG = new File("temp.png");
    File initialFile = new File("test.jpg");
    Color blankColor = new Color(0, 0, 0, .0f);
    int diameter = 10;
    int mouseX = 0;
    int mouseY = 0;
    boolean mouseClicked = false;
    boolean fileCreated;
    WritableRaster myRaster;
    WritableRaster blankRaster;
    int[] emptySquare = new int[400];
    ColorModel colorModel = myImage.getColorModel();

    public MyFrame() {
        setLayout(new BorderLayout());
        setSize(800, 800);
        add(mp, BorderLayout.EAST);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
        setFocusable(true);
        addMouseListener(this);
        addMouseMotionListener(this);
        for (int x = 0; x < 10; x++) {
            for (int y = 0; y < 10; y++) {
                for (int b = 0; b < 4; b++) {

                    emptySquare[x * y * b] = 0x00000000;
                }
            }
        }
        myRaster = myImage.getRaster();
        blankRaster = blankImage.getRaster();

        try {

            myImage = ImageIO.read(initialFile);
            fileCreated = ImageIO.write(myImage, "png", tempPNG);
            myImage = ImageIO.read(tempPNG);

        } catch (Exception e) {
        }
    }

    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;

        g2d.setColor(Color.BLACK);
        // g2d.fillRect(0, 0, 300, 300);
        g2d.drawImage(myImage, 0, 0, 300, 300, null);

        // g2d.setColor(blankColor);
        // g2d.setPaint(Color.blue);

        // myImage.
    }

    private class MyPanel extends JPanel {

        private MyPanel() {
        }
    }

    @Override
    public void mouseClicked(MouseEvent m) {

        repaint();

    }

    @Override
    public void mouseEntered(MouseEvent m) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mouseExited(MouseEvent m) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mousePressed(MouseEvent m) {

        repaint();

    }

    @Override
    public void mouseReleased(MouseEvent m) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mouseDragged(MouseEvent m) {

        mouseX = m.getX();
        mouseY = m.getY();

        myRaster.setDataElements(mouseX, mouseY, blankRaster);
        myImage = new BufferedImage(colorModel, myRaster, true, null);
        myImage.setData(blankRaster);

        myRaster.setPixel(mouseX, mouseY, emptySquare);
        myImage.setData(blankRaster);
        AlphaComposite.getInstance(AlphaComposite.SRC_OVER, .1f);
        Graphics2D tempG2d = myImage.createGraphics();
        tempG2d.setComposite(AlphaComposite.Clear);
        // tempG2d.setColor(Color.blue);

        tempG2d.fillOval(mouseX, mouseY, diameter, diameter);

        // tempG2d.setColor(blankColor);
        // tempG2d.setComposite(AlphaComposite.Src);

        for (int i = mouseX; i < mouseX + diameter; i++) {
            for (int j = mouseY; j < mouseY + diameter; j++) {
                int white = 0xffffff;

                Color c = new Color(0xccFF0000, true);
                int color = myImage.getRGB(i, j) & 0x00ffffff; // use bitwise &
                // to remove
                // alpha
                // component
                myRaster.setPixel(mouseX, mouseY, emptySquare);
                myImage.setData(myRaster);

                // myImage.setRGB(i,j,color); // transparent white

            }

        }

        // tempG2d.fillOval(mouseX, mouseY, diameter, diameter);
        try {
            // fileCreated=ImageIO.write(myImage, "png", tempPNG);
        } catch (Exception e) {
        }
        repaint();
    }

    @Override
    public void mouseMoved(MouseEvent arg0) {
        // TODO Auto-generated method stub
    }
}

Answer 1

相反，使用 getPixel() 在底层 Raster 上，清除 alpha 字节，并使用 setPixel() 和更新后的数组。另请参阅此相关示例。