使用 alpha 颜色进行 Java 打印会生成空白页

Question

我遇到一个问题，当我使用 Alpha 值不是 100% 的颜色时，整个页面将无法打印。

例如

• 我有两个页面p1，p2。
• 我有一种 alpha 设置为 40% 的颜色，称为 c1。
• 我有相同的颜色，但 alpha c2 为 100%。
• 我有一个矩形r，它可能会也可能不会打印在页面上。

• 我还在两者上打印了一些测试文本。

• 如果p1不打印r，p2使用c2打印r，p2打印良好。

• 如果p1不打印r，p2使用c1打印r，p2不打印。
• 如果 p1 使用 c1 打印 r，p2 使用 c1 打印 r，p2 打印效果很好。

下面是一个示例应用程序来演示这一点：

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.RoundRectangle2D;
import java.awt.print.Book;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.print.PrinterJob;

import javax.swing.JButton;
import javax.swing.JFrame;

class Rectangle extends java.awt.Rectangle {
    public static final int SCREEN_RESOLUTION = 72;
    private static final int TWIP_CONVERT = 1440;

    Rectangle(int x, int y, int w, int h) {
        super(twip2pixel(x,1),twip2pixel(y,1),twip2pixel(w,1),twip2pixel(h,1));
    }

    static int twip2pixel(int twips, float zoom) {
         return Math.round(zoom * twips * SCREEN_RESOLUTION / TWIP_CONVERT);
     }
}

public class Test extends JFrame implements ActionListener{

    static Rectangle[] textRectangles1 = {
                new Rectangle(2590, 8075, 2325,265),
                new Rectangle(2480, 8480, 7595, 265),
                new Rectangle(1700, 8940, 8310, 265),
                new Rectangle(2445, 9385, 7615, 265),
                new Rectangle(2630, 9850, 7410, 265),
                new Rectangle(2015, 10320, 8005, 265),
                new Rectangle(2450, 10780, 7600, 265),
                new Rectangle(8210, 12240, 2170, 265),
    };

    static Rectangle[] textRectangles2 = {
                new Rectangle(1895, 5630, 6160, 265)
    };

    JButton btnPrint;
    JButton btnPrint2;
    JButton btnPrint3;

    public Test() {
        this.setLayout(new FlowLayout());

        btnPrint = new JButton("Print - 100% alpha - works");
        btnPrint.addActionListener(this);
        this.add(btnPrint);

        btnPrint2 = new JButton("Print2 - 40% alpha - doesn't work");
        btnPrint2.addActionListener(this);
        this.add(btnPrint2);

        btnPrint3 = new JButton("Print3 - both pages 40% alpha - works");
        btnPrint3.addActionListener(this);
        this.add(btnPrint3);

        this.pack();
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        Test test = new Test();
        test.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        PrinterJob job = PrinterJob.getPrinterJob();

        Book book = new Book();
        if(e.getSource().equals(btnPrint)) {
            book.append(new MyPage(textRectangles1, 255, false), new PageFormat());
            book.append(new MyPage(textRectangles2, 255, true), new PageFormat());
        } else if(e.getSource().equals(btnPrint2)) {
            book.append(new MyPage(textRectangles1, 255, false), new PageFormat());
            book.append(new MyPage(textRectangles2, 100, true), new PageFormat());
        } else {
            book.append(new MyPage(textRectangles1, 100, true), new PageFormat());
            book.append(new MyPage(textRectangles2, 100, true), new PageFormat());
        }

        job.setPageable(book);
        boolean doPrint = job.printDialog();
        if (doPrint) {
            try {
                job.print();
            } catch (PrinterException ex) {
                // The job did not successfully
                // complete
            }
        }
    }

    static void drawText(Graphics2D g, Rectangle r) {
        g.setClip(r.x, r.y, r.width, r.height);
        AffineTransform oldTransform = g.getTransform();
        g.scale(1.0, 1.0);
        g.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS,
                   RenderingHints.VALUE_FRACTIONALMETRICS_ON);

        g.translate(r.x, r.y);
        g.setFont(new Font("Arial",0,10));

        g.setColor(Color.BLACK);

        float y = g.getFontMetrics().getAscent() + 1;
        g.drawString("TEST", 3, y);

        g.setTransform(oldTransform);
    }

    static void drawBox(Graphics2D g, Rectangle r, int alpha) {
        AffineTransform oldTransform = g.getTransform();
        float zoom = 1;
        g.scale(zoom, zoom);
        g.setClip(r);
        g.translate(r.x, r.y);

        Font boxFont = new Font("Arial", 1, 30);
        g.setFont(boxFont);

        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

        RoundRectangle2D rect = new RoundRectangle2D.Double(0.0,0.0,r.getWidth()-2,r.getHeight()-2,15 ,12);
        g.setColor(new Color(188, 238, 104, alpha));
        g.fill(rect);

        g.setTransform(oldTransform);
        g.setFont(new Font("Arial",0,10));
        g.setTransform(oldTransform);
    }
}

class MyPage implements Printable{
    int alpha = 255;
    boolean printRectangle = false;
    Rectangle[] textRectangles;

    MyPage(Rectangle[] textRectangles, int alpha, boolean printRectangle) {
        this.textRectangles = textRectangles;
        this.alpha = alpha;
        this.printRectangle = printRectangle;
    }

    @Override
    public int print(Graphics graphics, PageFormat pageFormat,
            int pageIndex) throws PrinterException {

        Graphics2D g2d = (Graphics2D) graphics;

        g2d.setPaint(Color.black);
        g2d.translate(10, 10);
        g2d.scale(0.96732026, 0.96732026);

        for(Rectangle r : textRectangles) {
            Test.drawText(g2d, r);
        }

        if(printRectangle) {
            Test.drawBox(g2d, new Rectangle(4156, 942, 3728, 1216), alpha);
        }

        return Printable.PAGE_EXISTS;
    }
}

Answer 1

这是由 java bug 引起的：
https://bugs.java.com/bugdatabase/view_bug?bug_id=7146409

解决方法是在第一页上打印一个矩形，宽度和高度设置为 0，但图形颜色设置为 alpha 小于 255 的颜色。