Using Gallery Toolkits

[ktuli]

All,

This has come up a couple times when I've posted photos here for competitions and/or critiques. I finally took some time tonight to do some testing, and I must say that the results are quite interesting.

Basically, I use the website tool - Gallery 2 to store and share all of my photos. One of the resized versions it creates by default is 640 pixels on the longest edge. But apparently the toolkit that I'm using to do the resizing is doing a lot of other changes to the files as well. Take a look...

Original File manually resized to 700x467


Gallery GD Toolkit resized to 640x427


Quite the difference, no?

So my questions are...

1. Does anyone else here use Gallery?

2. Does anyone have any experience with any of the following toolkits:

• ImageMagick
• NetPBM
• Gd
• Dcraw
• Jpegtran

After seeing the horrible performance I am getting from Gd, I have to find an alternative to feel like I can continue using Gallery like I do, and I'll probably end up testing out each of these toolkits, but I was wondering if anyone had experience and could point me in a direction first.

Thanks in advance!

- Bill

[PaulMiller]

I'm not familiar with Gallery, but your problem is that it is removing the ICC profile information from the resized file. Your manually resized file is tagged with the Adobe RGB profile, the Gallery resized image has no profile. If I add an Adobe RGB profile to the Gallery image, the two images look very similar. This suggests to me that Gallery is ignoring colour profile information in the files.

- Paul

[revi]

I don't use Gallery.

I do use ImageMagick (convert tool) and that leaves metadata (including colourspace) intact. I also have used dcraw, but that's only for developing RAW files, not for resizing or otherwise modifying 'normal' image files (afaik).

The other three I haven't used to the best of my knowledge (though they may have been used by other programs 'under the hood': the packages are installed).

Hope this helps,

Remco

[Dave Humphries]

Hi Bill,

The other thing to bear in mind is what jpg quality does each method use?
The 640 one looks to be much lower quality than the first (manually saved) one.

Are you re-sharpening after the down size?
How much are you downsizing by? e.g. full res pixel length/700? (and uploaded pixel length/640? )

Cheers,

[ktuli]

Paul - Thanks for spotting that. It looks like that is probably the problem.
Remco - Thanks for the pointer. I decided to test ImageMagick first, and I think it might be worth sticking with that.
Dave - I think you may have something there, but at least for my tests below, I personally don't see any difference between the different quality settings, though it does have a difference in size.

So anyway, here's the deal. I was using Gd at quality setting 75 before, and apparently it kind of sucks. I've tried different quality settings, and then started trying ImageMagick.

On a normal basis, I am using this to generate thumbnails and resized versions for my gallery and for use on my blog and possibly if the quality is acceptable for sharing places like here. The originals are the fullsize images out of my 7D, so 5184x3456. For the test though, I ran it just on a 700x467. The resized versions are always the 640x427 size (though when I upgrade to Gallery3, I may increase that size).

Anyway, here are the results. If anyone can take a look and see if you can identify differences, I'd really appreciate it.

Original File manually resized to 700x467, 164 kb


Gd resized to 640x427 at quality 75, 20 kb


Gd resized to 640x427 at quality 100, 120 kb


ImageMagick resized to 640x427 at quality 90, 56 kb


ImageMagick resized to 640x427 at quality 95, 80 kb


ImageMagick resized to 640x427 at quality 100, 212 kb (larger than original!)


Any thoughts? I think I am leaning towards just leaving things at ImageMagick at a quality level of 90 since I don't really see a difference between 90 and 100.

- Bill