在Java環(huán)境中,可以使用 java.awt.Toolkit.getScreenResolution()可以得到屏幕每英寸的象素數(shù),但是好像沒有什么方法能知道某一臺打印機(jī)的分辨率,更別提去控制打印粒度了。于是可恥的使用著丑陋的缺省打印精度幾年后,終于找到了解決方法,不知道該高興還是悲傷,其原理說出來也是非常的簡單:
提高打印精度,其實(shí)就是把本來是A3紙的內(nèi)容往A4紙里畫,也就是說,打印區(qū)域(這里對應(yīng)著Java里的Graphics對象)需要縮小,然后由于缺省情況下打印是照72DPI來打的,不做改變的話,打印內(nèi)容也會跟著變小。這樣就不是我們想要的效果了,所以還得把打印內(nèi)容成比例放大。一個縮小,一個放大,于是畫完后,在指定大小的紙張內(nèi),便容納了比以往更多象素的內(nèi)容,這下世界總算完美了。
以上做法形象的說應(yīng)該是這樣:把需要產(chǎn)生的圖形對象先放大,畫在一張“紙上”,然后整體縮小,這樣精度就提高了。
tips 1:在一般企業(yè)報表表格打印中,使用144DPI得到的表格線的寬度看起來最舒服。
tips 2:現(xiàn)在號稱600DPI的打印機(jī)其實(shí)是576DPI,如果想使用這個分辨率的精度,需要用好一點(diǎn)的紙張,因?yàn)橐呀?jīng)到極限了,紙張稍差點(diǎn),打印墨粉就沾不上,導(dǎo)致線體殘缺。
附源碼(修改分辨率就改動變量iResMul就好):
import java.awt.*;
import java.awt.print.*;


public class MyPrintableObject implements Printable
{
public int iResMul = 1; // 1 = 72 dpi; 4 = 288 dpi

public int print(Graphics g, PageFormat pf, int iPage)

throws PrinterException
{
final int FONTSIZE = 12;
final double PNT_MM = 25.4 / 72.;
if (0 != iPage)
return NO_SUCH_PAGE;

try
{
int iPosX = 1;
int iPosY = 1;
int iAddY = FONTSIZE * 3 / 2 * iResMul;
int iWdth = (int) Math.round(pf.getImageableWidth() * iResMul) - 3;
int iHght = (int) Math.round(pf.getImageableHeight() * iResMul) - 3;
int iCrcl = Math.min(iWdth, iHght) - 4 * iResMul;
Graphics2D g2 = (Graphics2D) g;
PrinterJob prjob = ((PrinterGraphics) g2).getPrinterJob();
g2.translate(pf.getImageableX(), pf.getImageableY());
g2.scale(1.0 / iResMul, 1.0 / iResMul);
g2.setFont(new Font("SansSerif", Font.PLAIN, FONTSIZE * iResMul));
g2.setColor(Color.black);
g2.drawRect(iPosX, iPosY, iWdth, iHght);
g2.drawLine(iPosX, iHght / 2 + iWdth / 50, iPosX + iWdth, iHght / 2
- iWdth / 50);
g2.drawLine(iPosX, iHght / 2 - iWdth / 50, iPosX + iWdth, iHght / 2
+ iWdth / 50);
g2.drawOval(iPosX + 2 * iResMul, iHght - iCrcl - 2 * iResMul,
iCrcl, iCrcl);
iPosX += iAddY;
iPosY += iAddY / 2;
g2.drawString("PrinterJob-UserName: " + prjob.getUserName(), iPosX,
iPosY += iAddY);
g2.drawString("Betriebssystem: " + System.getProperty("os.name")
+ " " + System.getProperty("os.version"), iPosX,
iPosY += iAddY);
g2
.drawString("Java-Version: JDK "
+ System.getProperty("java.version"), iPosX,
iPosY += iAddY);
g2.drawString("Width/Height: " + dbldgt(pf.getWidth()) + " / "
+ dbldgt(pf.getHeight()) + " points = "
+ dbldgt(pf.getWidth() * PNT_MM) + " / "
+ dbldgt(pf.getHeight() * PNT_MM) + " mm", iPosX,
iPosY += iAddY);
g2.drawString("Imageable Width/Height: "
+ dbldgt(pf.getImageableWidth()) + " / "
+ dbldgt(pf.getImageableHeight()) + " points = "
+ dbldgt(pf.getImageableWidth() * PNT_MM) + " / "
+ dbldgt(pf.getImageableHeight() * PNT_MM) + " mm", iPosX,
iPosY += iAddY);
g2.drawString("Imageable X/Y: " + dbldgt(pf.getImageableX())
+ " / " + dbldgt(pf.getImageableY()) + " points = "
+ dbldgt(pf.getImageableX() * PNT_MM) + " / "
+ dbldgt(pf.getImageableY() * PNT_MM) + " mm", iPosX,
iPosY += iAddY);
g2.drawString("versuchte Druckaufl sung: " + 72 * iResMul + " dpi",
iPosX, iPosY += iAddY);

} catch (Exception ex)
{
throw new PrinterException(ex.getMessage());
}
return PAGE_EXISTS;
}


private static double dbldgt(double d)
{
return Math.round(d * 10.) / 10.; // show one digit after point
}


public static void main(String[] args)
{
PrinterJob pj = PrinterJob.getPrinterJob();
pj.setPrintable(new MyPrintableObject());

if (pj.printDialog())
{

try
{
pj.print();

} catch (PrinterException e)
{
System.out.println(e);
}
}
}
}
