[PDFBOX-942] Image quality improvements

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.4.0
• Fix Version/s: 1.5.0
• Component/s: PDModel
• Assignee: Andreas Lehmkühler
• Reporter: Olivier DOREMIEUX
• Created: 14/Jan/11 17:27
• Updated: 04/Mar/11 10:29
• Resolved: 30/Jan/11 17:10

Description

The quality of the images inserted in a PDF documents could be improved by changing PDJpeg.java
In the API
public PDJpeg(PDDocument doc, BufferedImage bi) throws IOException

ImageIO.write(bi, "jpeg", os);

could be replaced by :

ImageWriter writer = null;
Iterator iter = ImageIO.getImageWritersByFormatName("jpg");
if (iter.hasNext())

{ writer = (ImageWriter) iter.next(); }

ImageOutputStream ios = ImageIO.createImageOutputStream(os);
writer.setOutput(ios);

// Set the compression quality
JPEGImageWriteParam iwparam = new JPEGImageWriteParam(Locale.getDefault());
iwparam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
iwparam.setCompressionQuality(1.0f);

// Write the image
writer.write(null, new IIOImage(bi, null, null), iwparam);

writer.dispose();

This increase the size of the generated PDF.
By default the JPEG quality is 0.75, in the patch I use 1.0, the maximum quality
As a suggestion the quality of the JPEG could be a global variable since it affect the size of the PDF