[PDFBOX-738] Preserve transparency when converting to image with rgba

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.2.0
• Component/s: PDModel
• Labels: image pdf
• Environment: all
• Assignee: Unassigned
• Reporter: Armando Singer
• Created: 02/Jun/10 05:31
• Updated: 01/Jul/10 07:27
• Resolved: 03/Jun/10 10:59

Description

When converting a pdf page to an image, the transparency is lost because PDPage.drawImage() sets the background color to white: graphics.setBackground( Color.WHITE );

The desired behavior is to preserve transparency when rgba color is set, and to fall back to white when rgb is used.

The following change works with either color mode:

+
+ /**
+ * Fully transparent that can fall back to white when image type has no alpha.
+ */
+ private static final Color TRANSPARENT_WHITE = new Color( 255, 255, 255, 0 );
+
private COSDictionary page;

/**
@@ -706,7 +711,7 @@

BufferedImage retval = new BufferedImage( widthPx, heightPx, imageType );
Graphics2D graphics = (Graphics2D)retval.getGraphics();

• graphics.setBackground( Color.WHITE );
  + graphics.setBackground( TRANSPARENT_WHITE );

Attached is a patch and some sample pdfs and images.