TECH wrote: > Can you add a feature in Open Office to Compress images inside of a > document?
Daniel Carrera wrote:
Images don't compress well, unless you are willing to use a lossy format like JPEG. If you go that route, you will be losing image quality, and if we do that we'll get hate-mail.
Jonathan Hudson wrote:
Images in documents are (AFAIK), PNG (compressed) or JPEG (lossy compressed); then the document is compressed. Seems pretty opitimally compressed to me. How do you think OO.o might compress images further?
Allow me to venture an argument in favor of such a feature. I've only used it once in PowerPoint 2003, but I found it handy.
* How Handy? * A friend handed me a PowerPoint presentation in the ballpark of 110MB. (!) After running 'Compress Images' I handed back a copy that was a mere 16MB.
* How does PowerPoint do it? * I can't speak authoritatively, but I'll offer my impression, using my friend's horrendous .ppt file as an example.
'Compress Images' appears to work on images in two ways:
#1) Scaling
This friend had pictures on probably every slide. Most of these are huge images that were scaled WAY down to fit in the slide. But it seems PowerPoint saves the full scale image data. Kind of like setting the height and width attributes in an HTML image element without actually scaling down the image. 'Compress Images' will actually rid the presentation file of the extraneous image data. So if you scaled your 1280x1024 image to 320x240, you no longer have a scaled down image - you have an actual 320x240 image.
#2) Resolution
If you are running your presentation on a Windows machine, chances are your
display is set to 96 dpi. So 'Compress Images' converts every 200, 600, 1200
dpi, etc. image down to 96 dpi, trimming serious file size while allowing the
images to appear the same when displayed as they would have originally.
Perhaps, Daniel, the hate-mail won't come if no one notices the difference? :)
Then again, 'Compress Images' is a feature that the user has to /choose/ to run
on an existing file, so those users who want to save the higher quality image
data can keep it that way with no extra effort. In my situation I copied the
humongous file and ran 'Compress Images' on a copy, leaving the original
untouched and giving me a more portable copy (one that loads much faster, too).* Drawbacks to this Function *
#1 means the user needs to make sure all images Compressed will not need to be enlarged later. But since the images do not need to be changed after initial creation in many presentations, this is not a major problem.
The loss of quality in #2 could become noticeable to the viewer if the images are subsequently used for a purpose other than display - but that would seem to be outside the usual aim of an Impress presentation. Again, not a serious problem.
* Should OOo Have a Compress Images Feature? * I don't know, but it seems like it could only be a benefit to users. I don't know if the bloated file size was simply the result of the way PowerPoint deals with images. Perhaps it is not an issue with OOo. Nor do I know if Impress handles images in some unique way that would have kept the file size down. Perhaps someone with more knowledge in this area can address these points.
// Trevor Farlow
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