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Old 05-21-2012, 04:57 PM
Paul Hartman
 
Default merging or fitting images together

On Mon, May 21, 2012 at 11:31 AM, Michael Mol <mikemol@gmail.com> wrote:
>
> I'm seriously wondering if there might not be something broken with
> the .jpeg files I'm spitting out. That laptop (saffron) is in the
> middle of an overdue emerge --update --deep --newuse @world, though.
> (And I saw it was complaining about 19 blockers...) It may be overdue
> for a depclean and some other maintenance. I haven't tweaked things
> much, as it's my last functioning Gentoo box until I get kaylee and
> inara fixed.

It looks like the file uses arithmetic coding, which has legal
restrictions (patents, licensing, blah), which means many jpeg
implementations do not support it. That probably is why it works in
some places and not in others. You should pretty much always use
Huffman coding instead of Arithmetic coding if you're using the images
on the internet or sharing them with others. The image quality is not
affected by this choice, only the way the data is stored in the file.
The file size will be slightly larger using Huffman, but in most cases
only barely larger.
 
Old 05-21-2012, 05:16 PM
Michael Mol
 
Default merging or fitting images together

On Mon, May 21, 2012 at 12:57 PM, Paul Hartman
<paul.hartman+gentoo@gmail.com> wrote:
> On Mon, May 21, 2012 at 11:31 AM, Michael Mol <mikemol@gmail.com> wrote:
>>
>> I'm seriously wondering if there might not be something broken with
>> the .jpeg files I'm spitting out. That laptop (saffron) is in the
>> middle of an overdue emerge --update --deep --newuse @world, though.
>> (And I saw it was complaining about 19 blockers...) It may be overdue
>> for a depclean and some other maintenance. I haven't tweaked things
>> much, as it's my last functioning Gentoo box until I get kaylee and
>> inara fixed.
>
> It looks like the file uses arithmetic coding, which has legal
> restrictions (patents, licensing, blah), which means many jpeg
> implementations do not support it. That probably is why it works in
> some places and not in others. You should pretty much always use
> Huffman coding instead of Arithmetic coding if you're using the images
> on the internet or sharing them with others. The image quality is not
> affected by this choice, only the way the data is stored in the file.
> The file size will be slightly larger using Huffman, but in most cases
> only barely larger.

I'm familiar with the difference between Huffman and arithmetic[1]. I
don't recall seeing any options for managing it, though. I'd have to
check to find out what USE flags I've got enabled that might be
involved. Also surprising that Windows 7 won't process it.

[1] Side effect of having a crazy compression geek for a friend and
coworker. I think he finally got around to trying my suggestion of
saving off the deflate window state for seekable .tar.gz files.
--
:wq
 

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