I'm not too strong with the use of the image libraries (GD in this case), so bear with me.

I've noticed that when I upload images in Zenphoto, they look as intended at full size, but they are washed out when viewed in the "normal" mode (default template) where they are resized to a width of 595 pixels.

For example:
http://photos.bradybouchard.ca/2008/sulphur_gates_hdr_1.jpg.php?p=*full-image
versus:
http://photos.bradybouchard.ca/2008/sulphur_gates_hdr_1.jpg.php

As best as I can tell, Imagemagick does a much better job of resizing images without losing colour. Since Imagemagick isn't an option (yet), I'm wondering if anyone has some tips for using GD (modifying the zenphoto processing php files somewhere) that can give proper colour when resizing without looking washed out?

Thanks.

I see no difference in color between the full-size and resized image in your example. Both are identical; and don't worry, my monitor is color-calibrated and my eyes are good.

Ah, but I'm using Firefox3 with color profile support turned on.

My guess is that you're seeing a color profile mismatch. You should use the sRGB colorspace for JPEGs you upload to the web. If you're using AdobeRGB or ProPhoto RGB, you need to convert to sRGB first to preserve the correct colors.

See here:
http://www.gballard.net/psd/go_live_page_profile/embeddedJPEGprofiles.html
And similar problems:
http://flickr.com/groups/central/discuss/72157594558647393/

Awesome, thanks for the help! Now that you mention it, that makes perfect sense.
From my very limited testing at the moment here, my fresh build of FF3 renders both the resized and full-sized images washed-out, and Safari renders the images like I stated above - the resized one is washed-out, but the full-size one has proper colour.

It looks like Safari will only use the embedded colour profile when the image is linked directly. I'll take another look at this this afternoon and post my findings here to help anyone else out with this problem.

Thanks again for your help!

Hi, I was browsing the forum if someone mentioned that problem before.
I checked my gallery with Safari und FF3 (all Mac).
To me it appears as if the cached images lose their color profile when being generated.
I downloaded one of them an checked in Photoshop.
I created one of this 595px pics in PS, taking care of the proper sRGB profile, uploaded it to the cache et voila proper colors also in the standard view (default theme).
(Originals always have been ok)
What do I miss?
I looked for a configuration setting but didn't find something related to this.
Thanks a lot, Michael.

Well, Safari is a little problematic since it uses embeeded color profiles if available, FF3 can if told so, too.

Do you save your images via the "Save for web" (or how it's called in english) function? If it is washed out in the preview there is probably something else not right. The GDlib Zenphoto uses for resizing does not take care of profiles.

Everything you do for the web should be in sRGB, if so you are never going to run into problems with color mismatch between browsers. It does not matter if the color profile is stripped from the file then it is always going to be seen as sRGB.

The final word...:-)

Guys, I'm with you!
What I'm trying to say is, that I can't find any profile in the reduced size pics (checked with PS) while I can see the sRGB profile in the original images.
Hence the difference in color when viewing in either original size or reduced size (desaturated colors).
Uploading an 595-image I created in PS with sRGB stored to the cache directory solves that, but that would be a real pain for a couple of hundreds of pictures.

PS: IMO its the other way round: if there's no profile information stored in the pic and the pic's colors are tuned appropriately then it doesn't make any difference if the browser displays it with a sRGB profile or not.
But if the image is prepared within the sRGB realm, there's a difference.
(but maybe I just don't get it :-( )

zenphoto, and most WEB applications are not color managed. Your only option is to stick with sRGB from the start.

There has to be something wrong in your Color management work flow, there should be no difference at all. Also worth noting that you wouldn't want the color profile with the file anyways, it makes it bigger, it depends on color profiles how big they are, some are huge.

Say you would use the color management of "FF Frontier Print sRGB, Fujifilm" for your work and Zenphoto would not strip down the color profile. then you would end up with thumbs in the gallery that are Thumb size + 800kb for the profile. That is a hefty load, the same would count for the single images, image size + 800kb. Then there are some much bigger profiles.

I took a look at the photo in the first post, no difference what so ever.

Hi, I'm not the thread starter, the images above are not mine.
I started to reply a couple of times but eventually didn't since I became pretty unsure about the kind of misconception I'm under.
What you say makes sense. Only that sRGB profiles are not that big.
Until now I published images as prints ... and I read things about websave colorspace etc.
And yes, you may be right, there might be a problem in my workflow.
Although I made sure that my camera outputs shots with sRGB profiles.
I'm happy with Zenphoto which (I thought) allows me to upload unedited images and automatically generates small size and thumbnail images especially for fast publising.
But then again I noticed the color difference to the processed images.
Maybe I've to change my workflow, but I have to keep it simple.
I'll do some further reading ... thanks so far (to all!).
Michael.

ahh sorry about that...

However if I can make some recommendations I would suggest to use the AdobeRGB in the camera as it is much bigger space. As well shooting RAW, but that's another subject.

http://arnaud.klinger.free.fr/photo/gestion_couleurs/adb98_srgb_gamut.jpg

I made a screen shot with some arrows.
If you use Photoshop I would recommend these settings, Red arrows I strongly recommend and blue I recommend but can be a bit different in witch country or continent you are, for printing sake.

see here.
http://img.skitch.com/20081021-1y8yr5ucdicsm2qmgerppa8867.jpg

If there is anything about this I am glad to help, even thought this here might not be the right place to talk about these things, you are welcome to get in touch with me straight.

Hi All, thanks for your replies and suggestions!

@ sbillard: yes, the apps are not color managed but some browsers finally are. But that doesn't make it easier since you can switch off this option in some (e.g. FF3). If GD just left the color profile information in the image untouched I'd appreciate that.
@ olihar: Yes, this gets off-topic. Sorry for that. I do use RAW and JPG+sRGB simultaneously straight from the cam. Thanks for this instructions! I'll get back to you specifically.

All in all I found most information on the web (and there's lots of them) somewhat contradictory if not confusing. If it wasn't my need to keep the workflow simple (ideally pics from the cam on the web) I would just strip the color profile, adjust the colours via soft-proof in PS and upload. But that's to much of a workload.

Thanks so much , Michael.

PS: see this one as well:
http://www.zenphoto.org/support/topic.php?id=2735&replies=8#post-24934
http://www.zenphoto.org/support/topic.php?id=3360