Re: [Gimp-developer] Gimp from git Gegl Gaussian Blur and Unsharp Mask useability issues

[Elle Stone <ellestone ninedegreesbelow com>]

On 12/03/2013 02:10 PM, Teo Mazars wrote:
> Hi,
>
> The way GEGL currently exposes each numerical parameters is as follow:
>
> 1) A nominal range, say [a, b], which represents the range where the operation is expected to work
> 2) An UI range, [a', b'] included in [a, b], representing the area of interest of the parameter.
> 3) An exponent, (like a gamma correction), to make the slider not behave linearly on the [a', b'] range.
>
> Currently, GIMP's sliders "show" only [a', b'], but allows values in [a, b]. The exponent is the way GEGL handles the 
> "mutli-scale" problem and it allows to have more precision on small value. Those values are all in GEGL, look for eg 
> gegl_chant_double_ui in /operations/common/*.c
>
> I will let others comment on what is the optimal UI range for those two operations. But changing [a', b'] would be really easy, 
> and it should change the "unit" as well. I am not sure about making that range "user configurable", it makes 
> sense imho.

That sounds like maybe I can change the slider scale in the source code 
pretty easily, even if it never gets changed in git. Thanks! I'll give 
that a try. The slider scales have been a constant issue. I thought I 
would get used to them, but that never happened.

> In the GEGL Gaussian blur, parameters are the std_dev along x and y, describing mathematically the Gaussian curve used 
> as kernel. Though, I have to read the code to know where the infinite curve is clipped to have a 
> "only-one-pixel" actual radius. Which is not obvious...
I'll have to look up what that means. Is there a simple approximate 
conversion to pixel radius?

> Other than that, I don't really understand the "Masks" comment. You can see the actual mask by checking "Show the 
> layer mask", but perhaps you want to see both the mask and the resulting image at the same time?

User error! "Show the layer mask works perfectly", exactly what I wanted 
right under my nose and I never noticed it. Gimp never ceases to amaze 
me. Thank you so much!

> Hah, and the "computational explosion" with bad parameters is a known bug in a lot of GEGL operations, it may even make 
> GIMP crash. It probably needs to be fixed in each operation individually, but this is not obvious... Perhaps we will need to make 
> the "process" step of GeglOperations cancellable at some point? Unclear...

Good to know it's a known issue.

> Also keep in mind that this is all "work in progress", Mitch once said that the ui infrastructure for GEGL 
> Operations in GIMP is not done. And most of GEGL Operations still need some love.

It did seem like it might be a good time for feedback on various ui 
issues, yes? no?


On 12/03/2013 02:45 PM, Joao S. O. Bueno wrote:
> Certainly it would be a lot better if while trying to click on the
> number to type in a new valuein the Gaussian Blur filter dialog in
> GIMP, you could not "accidentally" click on the bar bringnig the
> radius to 850, and having to wait several seconds until GIMP becomes
> responsive again.
>
>
> "accidentally" is quoted, because it is actually very hard not to make
> that happen. I know the widgets are pretty - no one can deny that -
> but maybe, just letting the typeable values lie outside the range of
> the slider would be a nice-enough fix already.

You are right to quote "accidentally"! It's really easy to have that 
accident happen. I have plenty of RAM, but my processors are slow and my 
graphics card isn't up-to-date. So those little accidents are painful 
and it can take considerably longer than several seconds to recover.

When I'm experimenting to find just the right value, I find it easier to 
make small experimental changes with a slider than with a box for 
typing, if the slider is set up with an appropriate range. Not to say 
everyone would feel that way, of course.

The flip side is that just as soon as the slider range is made smaller, 
one wants a larger range. I remember using some application that allowed 
to change the scale of a slider easily and instantly. It was very 
convenient.

Elle