Downscale compression artefacts [IMGWIDE]

[georgweb]

Hello all,

could you please share some experience on how to post pictures without compression artefacts? I basically understand that you can't trust any auto-compression but rather resize pictures in your preferred software. This is what I have resorted to basically. I have a dummy flickr account only to post pics in different sizes there and then link them here. I have also linked Picasa-pics but these show up sometimes and sometimes disappear, like with so many other 'free-pic' servers.

But: There is a practical feature in this forum to downsize pics with the 'imgwide' tag. Many people use it, it is handy, but it also produces quite severe artefacts, see an example here.

Instead of complaining to the guy who does it all on this forum (respective thread about imgwide-introduction) I'd rather reach for your expertise here and hope we can come up with one or two helpful ways to post pictures in pentaxforums-threads.

I imagine other open source software which could work inside this forums' software or some guidelines to avoid those artefacts. Maybe it is the easiest to use the webbrowsers' compression, but then there is so many of them. My dream would be another button in the advanced-posting window just like the 'imgwide', but with a much thorougher algorithm.

Thanks for listening, Georg (the other)

[dosdan]

This problem came up in this thread:

Brisbane City from Kangaroo Point Cliffs

At this stage it's better to avoid [imgwide] if your picture contains diagonals. The problem is that [imgwide] does a fast resize based on your current window size. If you resize your window and click on it again the displayed large version will fit the space. I presume the designers just chose a very quick method of resizing.

Dan.

[georgweb]

Thanks Dan,
you confirm what I expected. I'd say time for an algorithm-update on the imgwide-tag, but who's capable of doing this?

Here are reactions from the Takumar-thread were my example-pic is posted:

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Sadly, it's the reader's web browser that's doing the scaling. This doesn't reliably preserve fine details (such as the wires).
The most reliable workaround is to scale to 800px wide before posting.
troyz

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The most reliable workaround is to scale to 800px wide before posting.
places like zenfolio allow you to upload images up to 10 (or they might have bumped it up to 14 now) megabytes in size, and the cool thing is that a) they scale their web presentation to the size of YOUR screen and b) if you are viewing your own zenfolio page while logged in, when you right click an image you get additional features that regular viewers dont (unless the hack the code), like selecting a specified link to a specified scaled down size and their scaling algorithms are VERY GOOD, allowing you to never bother re-scaling them manually.
Gooshin

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I think flickr's scaling algorithms are nearly perfect, IMO.
jsherman999


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[troyz]

Originally Posted by georgweb

Here are reactions from the Takumar-thread were my example-pic is posted:

:::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::
Sadly, it's the reader's web browser that's doing the scaling. This doesn't reliably preserve fine details (such as the wires).
The most reliable workaround is to scale to 800px wide before posting.
troyz

FYI, the image in question (see http://www.pentaxforums.com/forums/357416-post710.html )
looks much better on Mac Firefox than on Windows Firefox (both version 2.0.0.17).

[georgweb]

Troyz you're right!

I had a look at the source code of the linked page, and yes you're right, seems like there is only the 'width'-tag responsible for resizing, so it's the browser's job.

<div align="center">

<a href="http://farm4.static.flickr.com/3056/2906312663_468268d8a8_o.jpg"

class="thickbox">

<img src="http://farm4.static.flickr.com/3056/2906312663_468268d8a8_o.jpg"

border="0" width="640"

alt="Click on the image to view it in a larger size" /></a><br

I use Firefox 2.0.0.16 (newer update don't work for me) and I-explorer 6.0 on a Windows-PC. On both the linked imgwide-pic look the same (badly cracked lines in upper image and moiré in the railroad ties).
As I could not find any add-ons for Firefox about this I'll just wait for the next stable version and see if there's any change in compression.
In the meantime I'll follow your advice in creating and linking a small and a large image.
Regards, Georg (the other)