Re: JPG file size increases with saving

[Greg Chapman <gregtutor@xxxxxxxxxxx>]

Hi Philip,

On 15 Jan 10 10:56 Philip Rhoades <phil@xxxxxxxxxxxxx> said:
> - When saving as JPG with 85% quality am I losing information?

Yes!
 
> - How can saving as JPG with 100% quality increase information (file
> size)?

It doesn't throw so much info away. It's not actually bigger than the 
the raw data (i.e. total pixels x colour depth)  Try saving the image 
as a BMP to get an indication of that.
 
> - Why is PNG so inefficient?

It's a lossless format (i.e. unlke JPG it doesn't throw any 
information away). It's not so much "inefficient", rather it just 
saves ALL the data.
 
> - imageinfo doesn't seem to be able to indicate information 
> structure /compression information differences between the files - 
> is there some way of doing this?

Not in any simple way. You're assumed to know the general benefits of 
the various file types for different purposes. There is some 
information in GIMP help. Best you read up some fuller descriptions of
the various image file formats. I'm sure someone be be along in a 
moment with some appropriate links.

Greg
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