Zip files

[wookie1965]

I have the Herschel 400 volumes 1 &2 in pdf format but they are both 30mb each I have tried 7zip to compress them to a size I can email when I check its compressed by 1mb  can someone tell me how to compress them to a size I can email please.

[Cornelius Varley]

PDF files don't compress well. Just tried it myself,  a 13917kb pdf compressed down to just 13741kb.

[vlaiv]

There is a maximum compression that can be achieved on a set of data - it is amount of information data actually holds - you can't write it smaller than that if you want to maintain whole information.

If data is already "tightly packed", or does not contain any redundancy in information storage - you can't do anything to compress it beyond what it will allow.

It looks like PDF is already very close to what is information content and can't be compressed further much.

[wookie1965]

Right thanks is there any other way to send it then so you dont get file too big to send message please.

[John]

Split them into a number of zip files ?

[Cornelius Varley]

6 minutes ago, wookie1965 said:

Right thanks is there any other way to send it then so you dont get file too big to send message please.

Upload them to Dropbox.

[vlaiv]

24 minutes ago, John said:

Split them into a number of zip files ?

+1

This is rather good way to do it if they contain sensitive information as you won't be leaving a copy on third party server

[wookie1965]

Thank you so much think I have sorted it now got a dropbox account and I think I have just shared both the pdf`s

[Louis D]

For future reference, if you are only concerned with the text in the document and not the illustrations and formatting which are what are taking up the majority of the 30MB, open the document in a PDF viewer, hit ctrl-a to select everything and ctrl-c to copy everything, open a new text file somewhere on your computer using notepad (on windows) and then hit ctrl-v to paste it all into it.  Save the file and tell it to lose any remaining formatting.  Next, compress it into a zip file.

I was able to take a 587KB PDF manual down to 27KB uncompressed and 10KB compressed with this technique.  Running the original PDF file through compression decreased it to 537KB.  PDF files typically contain illustrations and formatting information that won't compress much at all because it's already stored in a compressed format internally to the document.  It's really only the text that can be compressed.