Q: We are implementing the PDF Optimizer and I wanted to know the
difference between the numeration values
pdftron.PDF.Optimizer.ImageSettings.CompressionMode
e_retain
e_flate
e_jpeg
e_jpeg2000
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A: CompressionMode is used in SetCompressionMode() to indicate the
compression method used to compress uncompressed or down-sampled
images (or if the image recompression is forced - using
ForceRecompression ()).
The default value, e_retain is used to preserve the default
compression method (i.e. images compressed as Flate will say Flate,
images compressed as Jpeg2000 will stay Jpeg2000 etc). By using
e_jpeg instead of e_retain you could make sure that all recompressed
images use JPEG compression which could have positive effect on file
size (but may affect image quality).