Why does the PDFNet Optimizer create such large JPEGs?


I’ve optimized a file both in Acrobat and PDFNet. In each, I set the options to prefer JPEG compression. (In PDFNet, this is done with Optimizer.ImageSettings.SetCompressionMode(e_jpeg).) I set the PDFNet compression level to 9 (using Optimizer.ImageSettings.SetQuality()) and the Acrobat compression level to “Medium”. The PDFNet output is much larger. Why?


After analyzing the quality of JPEGs output from PDFNet and Acrobat at different levels, it seems that Acrobat’s “Medium” level approximates PDFNet’s quality level “3”. Here is a table of the correlations we’ve found between settings in each:

Acrobat … PDFNet
Minimum … 1
Low … 2
Medium … 3
High … 4-6
Maximum … 7-9

At these settings, Acrobat and PDFNet also create similarly-sized JPEGs.