[PDFBOX-5378] Slow rendering due to rescaling

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.0.25
• Assignee: Unassigned
• Reporter: Oliver Schmidtmer
• Created: 17/Feb/22 17:17
• Updated: 18/Feb/22 14:44

Description

Due to changes for better image quality when images are scaled down in https://svn.apache.org/viewvc/pdfbox/branches/2.0/pdfbox/src/main/java/org/apache/pdfbox/rendering/PageDrawer.java?r1=1877290&r2=1877289&pathrev=1877290 the attached PDF renders much slower.

I propose to replace image.gerScaledInstance by

public BufferedImage getRescaledImage( BufferedImage image, int w, int h ) throws IOException {
 float scaleW = w / (( float )image.getWidth());
 float scaleH = h / (( float )image.getHeight());
 if(scaleW < .5f || scaleH < .5f){
  int nextW = scaleW <.5f ? ( int )Math.ceil( image.getWidth() / 2.0 ) : w;
  int nextH = scaleH <.5f ? ( int )Math.ceil( image.getHeight() / 2.0 ) : h;
  image = getRescaledImage( image, nextW, nextH );
 }
 int type = (image.getTransparency() == Transparency.OPAQUE) ?  BufferedImage.TYPE_INT_RGB
 : BufferedImage.TYPE_INT_ARGB;
 BufferedImage scaled = new BufferedImage( w, h, type );
 Graphics2D g = scaled.createGraphics();
 g.setRenderingHint( RenderingHints.KEY_INTERPOLATION,  RenderingHints.VALUE_INTERPOLATION_BILINEAR );
 g.drawImage( image, 0, 0, w, h, null );
 return scaled;
}

While this implementations seems to be a bit slower than getScaledInstance, the call to graphics.drawImage with the resulting BufferedImage seems to be significantly faster than drawing the ToolkitImage.

Issue Links

• relates to: PDFBOX-4516 PDFBox text and images are blurry even after rendering with high DPI