Re: [Gimp-user] Test images and test suite (was Re: [Gimp-developer] GIMP should fork babl and GEGL)

[Elle Stone <ellestone ninedegreesbelow com>]

On 11/07/2014 10:25 AM, Jehan Pagès wrote:
> > >A good test suite of "copyleft" images would be a nice thing to have,
> > >whether for testing new and existing editing algorithms, or for whatever
> > >testing that individual GIMP users might want to do on their own
> > >(printer-related, for example).
> That's a good idea. What kind of images would be the most interesting?
> Basically should that be images, taken with a good digital camera, of
> a lot of objects of various colors?
> It could also be images with color gradients, I guess (sunset/rise and such)?
> Or do you already have such copyleft images at your disposal that you
> could provide?
> Indeed if we could gather these for access to anyone as reference
> (then various software could use them for their own tests), it would
> be great.
>
> Jehan

Nicolas Robidous's test image collection is very nice, in particular the 
baby's face and the brightly colored buildings make great test images. 
His images are already converted to sRGB, which means they can't really 
fully exercise the color gamuts of reasonably decent printers and wider 
gamut displays.

I can make available "straight from the camera interpolated raw file, no 
enhancements added" images of very saturated (outside the sRGB color 
gamut) natural objects, mostly flowers.

I've also put together various artificial color ramps, granger rainbows, 
stepped gray scales, and such. And I have IT8 target shots from several 
cameras, which I think the photographers would release under an 
appropriate license.

I wish that I had a nice set of pictures of people's faces, young to 
old, male and female, of diverse skin colors. Skin tones are something 
that everyone wants to get "just right", so faces make great test 
images. Such photographs ideally would be shot raw under natural 
daylight, more or less full frame, and properly white balanced, 
preferably with a white balancing object discretely placed somewhere in 
the image frame (styrofoam cups, PVC plastic, white coffee filters all 
work really well, often as well as commercially available white 
balancing aids).

High quality images with good gradients would be a nice addition to a 
collection of test images. Interpolated raw files that have been output 
in a wider gamut color space would be more versatile than images that 
have already been converted to sRGB.

Here are links to some sample collections of copyrighted test images:

http://www.pcstats.com/articleimages/200601/samsungspp2040_300dpi1.jpg

I would love to have enough copyleft images to put together a copyleft 
composite similar to the one in the above link.

http://www.northlight-images.co.uk/article_pages/test_images.html

http://www.outbackphoto.com/printinginsights/pi048/essay.html


Thinking more about "what kind of images", it depends on who's testing 
what. Here are some possible reasons for wanting test images:

* Testing scaling algorithms.

* Testing ICC profile conversions from wider gamut color spaces to 
printer profiles and/or to display screen profiles.

* Testing the quality of prints made by a commercial or personally owned 
printers.

So the first question is: What kind of test images, for what kinds of 
testing, do you all, as a diverse group of GIMP users and developers, 
wish you had access to?

Elle