I have just tried compressing a folder of images within Yosemite and the zipped archived folder that results is only a few MB short of the original which was 1.7 GB,
I have checked I have permissions to read/write the file content.
Is this the best I can expect from this facility?
iMac (21.5-inch, Late 2013), OS X Yosemite (10.10)
The Finder -> Control-Click -> Compress is Zip compression
As Barney-15E has mentioned, there are other compression utilities available from the Applications -> Utilities -> Terminal command line interface
man zip
man gzip
man bzip2 # can get some serious compression with --best option
man compress # the original Unix compression, which is not very good by today's standards
Depending on what was being compressed, over the years, I've seen different compression utilities be the best for that specific file collection, and then be not so good for a different collection of files. Generally if I have time, I'll often go with bzip2 --best, but it does take longer than other compression utilities.
NOTE: This is from a Unix command line perspective, not a Mac OS X GUI perspective, and not against 3rd party compression tools (I spend a lot of my work day working from a Unix command line, so I tend to use gzip and bzip2 in my scripts a lot).
Yosemite and Mavericks also have memory compression to keep more things in RAM. I do not know what algorithm is used for this compression:
<https://www.apple.com/osx/advanced-technologies/>
<http://arstechnica.com/apple/2013/10/os-x-10-9/17/>
The File System has a HFS+ Compression has been part of Mac OS X since Snow Leopard:
<http://hints.macworld.com/article.php?story=20090902223042255>
<http://blog.fosketts.net/2009/09/11/bizarre-hfs-tricks-in-mac-os-x-10-6-snow-leo pard/>
<http://hints.macworld.com/article.php?story=20090902223042255>
To the best of my knowledge that is the world of Mac OS X built-in compression.
Yes, with images. They do not compress much. Furthermore, the settings of the compressor are not set for maximum compression. You would need to run the compressor on its own in order to change its preferences.
Thanks for that, can you tell me where I should look for compressor as a separate app or function on the iMAC? "compress this file" comes up as an option on the file menu of most apps but there does not seem any way to alter its settings.
The only effective way to compressed already compressed images it to convert the images to a lower resolution. Or find a more efficient image encoding that is more efficient.
Generic compression (zip, gzip, bzip2, stuffIt, etc...) cannot really do much to compress an image. And in some cases may actually make the file larger.
Compression works well on files that are not already compressed, especially things like documents with lots of text in them.
Thanks, I get the general drift about already compressed image files being practically incompressible by their very nature, but I now have to assume that the boys and girls at Apple have built in only one automatic level of compression within the main operating system when it comes to other files and documents. This may not be a big issue, but I just wanted to be sure there was nothing else available with in the OS to allow manipulation of this if I ever felt the need.
Also understand that many images are already in a compressed format, like jpegs. Same with many PDF files.
Zip is available, as is tar, gzip…probably more.
But the command line may be too advanced for you.
Thanks for your detailed answer, it does expand nicely on the other respondents comments and I am now fully in the picture!
Compression not very compressed!
