Lossy Compression and Document Size

[Voltage Spike]

This message is simply a request for information.

The "Images" section of the document properties allows:


Lossy compression enabled, but don't compress
Lossy compression disabled


I would think the two options would provide similar results, but the former option can cut the document size nearly in half. I am fairly sure that the images are not compressed in either case because they seem to load in approximately the same amount of time.

What is the difference between the two, then?

Thanks in advance.

[iSilo]

Not sure I understand the exact settings you are asking about. If compression is disabled, then no type of compression, not even lossy compression is applied.

Could you please clarify on the exact settings you are asking about from the Images properties for the below options and/or others you are referring to?

[] Compress (optional lossy compression)
Lossy compression: []

[Voltage Spike]

Images\Options\Compress: Unchecked
Images\Options\Lossy Compression: Not available
File size: 13.1MB

Images\Options\Compress: Checked
Images\Options\Lossy Compression: None
File size: 3.1MB

The difference is quite dramatic in this example. I would expect both sets of options to produce identical files.

[iSilo]

For the first set of options, absolutely no compression is applied to images. This means that neither lossy nor lossless compression are applied.

For the second set of options, although lossy compression is not applied, lossless compression is still applied. So the reduced file size is because the lossless compression reduces the size of the images.

[Voltage Spike]

That seems very obvious now that you say something. :)

By the way, congratulations on your implementation of lossless compression. While lossy compression greatly slows down image rendering on my PalmOS device, the lossless compression results in instantaneous rendering.