Yes, there is a difference. By default FOP uses a "native" image loader
for JPG but not for PNG. There is however a native image loader for PNG
too, which you can enable in the configuration file. See
http://wiki.apache.org/xmlgraphics-fop/HowTo/ImageLoaderRawPNG for more
info. Try it and I expect that you will see a performance improvement.
Native image loaders process the image differently and usually do it
faster. The reason the native image loader for PNG is not enabled by
default is because it does not support all types of PNG images, but
supports the most common, so very likely it will work with your images too.
Why is PNG more expensive than JPG to process? One reason is
transparency, which JPG does not support. To embed a PNG in PDF the
transparency bytes have to be separated from the RGB bytes, and then
both are embedded in the PDF as separated components. The other reason
is compression. When not using the native image loader, the PNG image
needs to be uncompressed and converted to a "plain" RGB bitmap. This
process can be very expensive.
On 10/16/13 7:39 PM, Roberto Cahanap wrote:
Hello everyone.
We have been trying to figure out why our pdf generation was taking so
long.
When we changed an image in the PDF from PNG to JPG, then it was much
faster.
Is there a difference in the way these two graphic formats are
processed in FOP?
Thank you for your responses.
-Roberto
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