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FORUMS Community Talk, Chatter & Official Stuff AMASS Forum Software Talk
Thread started 20 Jun 2017 (Tuesday) 18:37
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Avoid recompressing small images?

 
sploo
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Jun 20, 2017 18:37 |  #1

From: http://photography-on-the.net ...showthread.php?p=18​383016

Would it be possible for the forum software to avoid recompressing small (<=1280 pixels wide) JPEG images uploaded by users, where the file size is below some agreed level?

The example referenced above took a ~400KB file down to ~386KB, but at the expense of a fair bit of damage - which seems to me like the wrong decision in terms of storage space vs image quality.


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Pekka
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Post has been last edited 4 months ago by Pekka. 2 edits done in total.
Jun 27, 2017 14:35 |  #2

sploo wrote in post #18383081 (external link)
From: http://photography-on-the.net ...showthread.php?p=18​383016

Would it be possible for the forum software to avoid recompressing small (<=1280 pixels wide) JPEG images uploaded by users, where the file size is below some agreed level?

The example referenced above took a ~400KB file down to ~386KB, but at the expense of a fair bit of damage - which seems to me like the wrong decision in terms of storage space vs image quality.

Thanks for the input.

See http://photography-on-the.net ...showthread.php?p=17​983597 for a detailed explanation how we save uploaded images.

To not compress is not an option, even with small originals, sorry. 80% seems good for quality and loading speed. There is no point serving 400Kb+ images as there might be dozens on one thread page. Gallery pages in Flickr or GoDaddy are different type of page environments (one large image per page). Re-compression is also one form of security, as it "mangles" the original image bytedata.

I can of course see what can be improved the resize algorithms, and perhaps tune compression % with image size, but that is definitely something that does not happen in near future. The Robidoux settings are very good overall as the test photos in the post I liked to shows.

Also, all modern browsers do things to page's resized images, viewing the uploads at 100% (click the glasses) when browser zoom is at 100% is the only situation I make my decisions on.

And please note that all the above handles only images that are uploaded here, embedded photos are not touched in any way.


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sploo
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Jun 28, 2017 05:21 |  #3

Pekka wrote in post #18388280 (external link)
Thanks for the input.

See http://photography-on-the.net ...showthread.php?p=17​983597 for a detailed explanation how we save uploaded images.

To not compress is not an option, even with small originals, sorry. 80% seems good for quality and loading speed. There is no point serving 400Kb+ images as there might be dozens on one thread page. Gallery pages in Flickr or GoDaddy are different type of page environments (one large image per page). Re-compression is also one form of security, as it "mangles" the original image bytedata.

I can of course see what can be improved the resize algorithms, and perhaps tune compression % with image size, but that is definitely something that does not happen in near future. The Robidoux settings are very good overall as the test photos in the post I liked to shows.

Also, all modern browsers do things to page's resized images, viewing the uploads at 100% (click the glasses) when browser zoom is at 100% is the only situation I make my decisions on.

And please note that all the above handles only images that are uploaded here, embedded photos are not touched in any way.

Thanks - the security point is a good one.

The comparisons were made on the 100% views of the images. As you can probably see from my profile, I haven't uploaded many images myself ( :oops: ) but this wasn't the first time I've seen people comment that uploaded photos often show a clear reduction in quality.

That said - the few I have uploaded I've generally reduced in pixel width myself, and from the linked thread above it does seem to be the best compromise if uploading images (i.e. just recompressed by the forum, vs resized and recompressed).

I appreciate the timescale issue regarding looking at tuning the compression - every coding and testing job is trivial... when you're asking someone else to do it ;-)a


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Pekka
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Jun 28, 2017 16:03 |  #4

sploo wrote in post #18388738 (external link)
Thanks - the security point is a good one.

The comparisons were made on the 100% views of the images. As you can probably see from my profile, I haven't uploaded many images myself ( :oops: ) but this wasn't the first time I've seen people comment that uploaded photos often show a clear reduction in quality.

If (any of) you have some clear examples of that problem, please PM me links to the originals and I'll get some test material.


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sploo
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Jun 29, 2017 02:19 |  #5

Pekka wrote in post #18389186 (external link)
If (any of) you have some clear examples of that problem, please PM me links to the originals and I'll get some test material.

Pekka - see the images in http://photography-on-the.net ...showthread.php?p=18​382720, and my original analysis in http://photography-on-the.net ...showthread.php?p=18​383016

Image #3 in LJ3Jim's post is effectively an original (though 1280 pixels wide, but it could be used to compare against image #2 - which wasn't resized by the forum, but it was recompressed).

I'll PM LJ3Jim to see if he will send you the original, so the resize and recompression can be tested (i.e. the process that created image #1).


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Avoid recompressing small images?
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