Poor Thumbnail Quality

[rainsnick]

Hi

The thumbnails in my albums show severe jpeg artifacts whilst the main large images are fine. I am uploading images already sized to 600px wide jpegs.

Could this be to do with my ISP offering only GD1.4?

I have requested then to upgrade to GD2.0 - will this give me any improvements in thumbnail quality?

Nick Rains

www.rainspirit.com.au/gallery

[artistsinhawaii]

GD2 will improve the quality of your thumbnails considerably.  If you can afford to wait for your provider to upgrade to GD2, then that would be the way to go.

Otherwise there are a couple of options you could try.

1) Since your pictures are already resized to 600 px prior to uploading, you could set the jpg quality to 100% in CONFIG for resizing.  ( I wouldn't recommend this when uploading larger pics, but since your pics are already the normal_ size, it should only affect your thumbnail file sizes.

2) Once you have batch added your files.  Create thumbnails of the same files (from your originals) on your computer, prefacing each with "thumb_"   (Just make sure the max dimensions are the same.) then FTP them right over the ones created by coppermine.   DO NOT upload thumb_ pics prior to batch adding as the batch add utility will consider all such files as having already been added to the database.


Dennis

[rainsnick]

Thanks for the quick response Dennis.

I am waiting for the server upgrade, should be only a few days.

I tried your option 1 already, 100% in GD1.4 is still poor.

Option 2 is a very good idea, more work but will give better results. I imagine that no sharpening is done in the GD routine and IMHO this is critical to decent thumbnails. I suppose any automated process is less than optimal so making the thumbs first in PS makes sense.

I found the GD1 vs GD2 comparison in the FAQ and whilst the second image is smoother, it needs sharpening. I guess the moral is that if you want it doing well, do it yourself!

Thanks

Nick

[artistsinhawaii]

Stramm has a mod out in the mods section for better thumbnails.
In it, he addresses the sharpening aspect of thumbnails.

I don't know if it will work for gd1 though.
You may want to mosey on over there and check it out.

Dennis

[Joachim Müller]

What you describe as jpeg artefacts will probably go away when you have GD2, because what you currently have are not compression artefacts imo, but reduced pallette issues: GD1 is only using 256 colors, that's why your thumbs look strange. No need to fiddle with jpeg compression rate, you'll only get larger files with no visible improvements.
Remember that you will have to change from GD1 to GD2 in coppermine's config once your webhost upgrades, and you'll have to rebuild your existing thumbs using the admin tools then.
As a side-note: GD1 comes bundled with very outdated versions of PHP only, so I suspect that your webhost is not very concerned about security. I strongly recommend reviewing their setup closely after the upgrade: if they don't have the most recent stable versions of everything security-related on the server, I suggest looking for another webhost.