当我搜索问题时，不知何故 java 打印 API 受到限制，所有发送到打印机的图片必须以 72dpi 分辨率打印。我们使用jasper report打印文件，无论我们画多大的条形码，条形码阅读器都不会扫描它..有类似的经历吗？如何解决这个问题？
asabo
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5107 次
2 回答
4
您需要通过属性PrinterResolution指定打印机分辨率。您还应该知道源分辨率，以便正确转换，例如：
PrinterResolution pr = new PrinterResolution(300, 300, PrinterResolution.DPI);
于 2009-01-13T08:08:09.303 回答
1
如果图像的元数据中没有预先定义的 DPI，Java 会将图像的 DPI 设置为默认的 java 72dpi，因此添加 MediaSizeName、PrinterResolution、MediaPrintableArea 属性以获得最佳效果是不够的，您还必须在其中添加图像的 dpi元数据，在这个答案的方法示例中就是这样：https ://stackoverflow.com/a/4833697/8792371 ：
private void setDPI(IIOMetadata metadata) throws IIOInvalidTreeException {
// for PMG, it's dots per millimeter
double dotsPerMilli = 1.0 * DPI / 10 / INCH_2_CM;
IIOMetadataNode horiz = new IIOMetadataNode("HorizontalPixelSize");
horiz.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode vert = new IIOMetadataNode("VerticalPixelSize");
vert.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode dim = new IIOMetadataNode("Dimension");
dim.appendChild(horiz);
dim.appendChild(vert);
IIOMetadataNode root = new IIOMetadataNode("javax_imageio_1.0");
root.appendChild(dim);
metadata.mergeTree("javax_imageio_1.0", root);
}
，然后确保在所需的可打印区域中打印其余属性，例如：
DocFlavor myFormat = DocFlavor.INPUT_STREAM.PNG;
// Build a set of attributes
PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
aset.add(MediaSizeName.ISO_A10);
aset.add(new MediaPrintableArea(0, 0, 35, 24, MediaPrintableArea.MM));
aset.add(PrintQuality.HIGH);
aset.add(new PrinterResolution(203, 203, PrinterResolution.DPI));
// adding other attributes
aset.add(OrientationRequested.PORTRAIT);
aset.add(new Copies(7));
aset.add(Fidelity.FIDELITY_TRUE);
有关更完整的示例：
import java.awt.EventQueue;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageTypeSpecifier;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.metadata.IIOInvalidTreeException;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.metadata.IIOMetadataNode;
import javax.imageio.stream.ImageOutputStream;
import javax.print.Doc;
import javax.print.DocFlavor;
import javax.print.DocPrintJob;
import javax.print.PrintException;
import javax.print.PrintService;
import javax.print.PrintServiceLookup;
import javax.print.ServiceUI;
import javax.print.SimpleDoc;
import javax.print.attribute.HashPrintRequestAttributeSet;
import javax.print.attribute.PrintRequestAttributeSet;
import static javax.print.attribute.ResolutionSyntax.DPI;
import javax.print.attribute.standard.Copies;
import javax.print.attribute.standard.Fidelity;
import javax.print.attribute.standard.MediaPrintableArea;
import javax.print.attribute.standard.MediaSizeName;
import javax.print.attribute.standard.OrientationRequested;
import javax.print.attribute.standard.PrintQuality;
import javax.print.attribute.standard.PrinterResolution;
import javax.print.event.PrintJobEvent;
import javax.print.event.PrintJobListener;
import javax.print.event.PrintServiceAttributeEvent;
public class PNGPrintingExample {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
try {
FileInputStream imageFile = null;
imageFile = new FileInputStream("E:\\1-and-2-1.png");
BufferedImage input = ImageIO.read(imageFile);
File output = new File("E:\\To-Be-Printed.png");
saveGridImage(output,input);
imageFile = new FileInputStream(output);
// Set the document type
DocFlavor myFormat = DocFlavor.INPUT_STREAM.PNG;
// Build a set of attributes
PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
// setting media size and printing media attributes
aset.add(MediaSizeName.ISO_A10);
aset.add(new MediaPrintableArea(0, 0, 35, 24, MediaPrintableArea.MM));
aset.add(PrintQuality.HIGH);
aset.add(new PrinterResolution(203, 203, PrinterResolution.DPI));
// adding some may be needed attibutes
aset.add(OrientationRequested.PORTRAIT);
aset.add(new Copies(7));
aset.add(Fidelity.FIDELITY_TRUE);
DocPrintJob job;
Doc myDoc = new SimpleDoc(imageFile, myFormat, null);
PrintService[] services =
PrintServiceLookup.lookupPrintServices(myFormat, null);
PrintService defaultPrintService = PrintServiceLookup
.lookupDefaultPrintService();
PrintService selectedPrintService =
ServiceUI.printDialog(null, 150, 150,
services, defaultPrintService, myFormat, aset);
if(selectedPrintService!=null)
{
System.out.println("selected printer:"
+selectedPrintService.getName());
try {
job = selectedPrintService.createPrintJob();
// Create a Doc
PrintJobListener pjlForP = new PrintJobListener() {
public void attributeUpdate(PrintServiceAttributeEvent e){
System.out.println("updated");
}
@Override
public void printJobNoMoreEvents(PrintJobEvent e){
System.out.println("may be sent to "+e.getPrintJob().getPrintService());
}
@Override
public void printDataTransferCompleted(PrintJobEvent pje) {
System.out.println("print Data Transfer Completed");
}
@Override
public void printJobCompleted(PrintJobEvent pje) {
System.out.println("The print job was completed");
}
@Override
public void printJobFailed(PrintJobEvent pje) {
System.out.println("The print job has failed");
}
@Override
public void printJobCanceled(PrintJobEvent pje) {
System.out.println("The print job was cancelled");
}
@Override
public void printJobRequiresAttention(PrintJobEvent pje) {
System.out.println("The print job require attention");
}
};
job.addPrintJobListener(pjlForP);
job.print(myDoc, aset);
imageFile.close();
} catch (PrintException ex) {
Logger.getLogger(BarcodePrintingFromJava.class.getName()).log(Level.SEVERE, null, ex);
}
}
else
System.out.println("selection cancelled");
} catch (FileNotFoundException ex) {
Logger.getLogger(BarcodePrintingFromJava.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(BarcodePrintingFromJava.class.getName()).log(Level.SEVERE, null, ex);
}
});
}
public static void saveGridImage(File output,BufferedImage gridImage) throws IOException {
output.delete();
final String formatName = "png";
for (Iterator<ImageWriter> iw = ImageIO.getImageWritersByFormatName(formatName); iw.hasNext();) {
ImageWriter writer = iw.next();
ImageWriteParam writeParam = writer.getDefaultWriteParam();
ImageTypeSpecifier typeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);
IIOMetadata metadata = writer.getDefaultImageMetadata(typeSpecifier, writeParam);
if (metadata.isReadOnly() || !metadata.isStandardMetadataFormatSupported()) {
continue;
}
setDPI(metadata);
final ImageOutputStream stream = ImageIO.createImageOutputStream(output);
try {
writer.setOutput(stream);
writer.write(metadata, new IIOImage(gridImage, null, metadata), writeParam);
} finally {
stream.close();
}
break;
}
}
public static void setDPI(IIOMetadata metadata) throws IIOInvalidTreeException {
// for PNG, it's dots per millimeter
double dotsPerMilli = 1.0 * DPI / 10 / 2.54;
IIOMetadataNode horiz = new IIOMetadataNode("HorizontalPixelSize");
horiz.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode vert = new IIOMetadataNode("VerticalPixelSize");
vert.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode dim = new IIOMetadataNode("Dimension");
dim.appendChild(horiz);
dim.appendChild(vert);
IIOMetadataNode root = new IIOMetadataNode("javax_imageio_1.0");
root.appendChild(dim);
metadata.mergeTree("javax_imageio_1.0", root);
}
}
您可以尝试注释或删除图像的 dpi 设置行，或保存在定义的 dpi 方法的行中，然后通过打印机进行打印作业，以获得差异，并在图像的元数据中定义定义 dpi 的价值，以及 java 如何对图像元数据中的 dpi 定义做出反应。
于 2018-04-11T15:20:18.190 回答