Re: how to detect if a jpeg file is progressive or not

[Wayne Topa <linuxone@intergate.com>]

H.S.(hs.samix@gmail.com) is reported to have said:
> Wayne Topa wrote:
> 
> > 
> 
> But converting a jpeg to progressive somehow has the effect that the
> progressive jpeg file is slightly smaller than the non-progressive one,
> but the client then uses up more RAM to reconstruct the image -- not
> that that will be a problem in most computers today.
> 

Oh.  Thanks for the that info..

> > convert -quality 25 infile.jpg outfile
> > 
> > That option got the 77K file down to 24K which is more manageable, for
> > me anyway.  I see no difference in the pictures but the size.
> 
> This is a case of compression with a loss in quality. Note that you can
> still have the new smaller image either as progressive or non-progressive.
> 

I don't see that loss in quality tho.  At 1280x1024 they look the
same, to these old eyes anyway, and the savings in size sure is a help
when you are sending images over a 26K POT line.

> I am still playing around to decide what size (in pixels) images to
> upload for others to view and how much quality to encode the jpegs with.
> In any case, I am planning to upload the larger size images only
> progressive jpegs no matter what quality I use them.

All of the inages on our web site are converted with the 'quality 25'
option.  I find a lot of sites with images that are 100K or more just
take too long to load.  There are still a lot of us that live in the
sticks and don't have access to anything but slow POT lines.  

Wayne

-- 
There are two ways to write error-free programs.  Only the third one works.
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