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https://issues.apache.org/jira/browse/PDFBOX-5378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17494158#comment-17494158
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Tilman Hausherr commented on PDFBOX-5378:
-----------------------------------------
The quality goes down with the change.
> Slow rendering due to rescaling
> -------------------------------
>
> Key: PDFBOX-5378
> URL: https://issues.apache.org/jira/browse/PDFBOX-5378
> Project: PDFBox
> Issue Type: Bug
> Reporter: Oliver Schmidtmer
> Priority: Major
> Attachments: PDFBOX-4516-new.png, PDFBOX-4516-old.png, Test_2.pdf
>
>
> 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
> {code:java}
> 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;
> }{code}
> 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.
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