Re: x11 palette inaccuracy?

[Daniel J S. <dan...@ie...>]

On 09/01/2013 03:04 PM, Ethan Merritt wrote:
>
>     >  I don't know which terminals other than x11 are affected by this.
>     Shouldn't it be effecting all terminals in the same way if the
>     problem lies in the core?  Why is the Qt terminal not showing this?
>     Dan
>
>
> The demo actually uses a palette of functions, not gradients. Most
> terminals calculate a pixel color directly from the functions.  But
> there is no way to pass the function definitions to gnuplot_x11, so
> instead the code in x11.trm pre-calculates a gradient by sampling the
> functions, and passes the gradient to gnuplot_x11.   I haven't looked to
> see if any other terminals do this also.

Ah...  It appears to be only the gnuplot_x11 terminal requiring the use 
of color function interpolation as:

#ifndef GPLT_X11_MODE
     case SMPAL_COLOR_MODE_FUNCTIONS:
	calculate_color_from_formulae(gray, color);
	break;
#endif /* !GPLT_X11_MODE */

I wonder if in this function:

calculate_color_from_formulae(double gray, rgb_color *color)

where the three components are computed whether the type of 
interpolation, linear or angular, can be controlled.

I'm still not sure that will work (it might).  The functions have to be 
retained post interpolation.  Once the function values are computed, 
doing interpolation has no assurance of selecting the user's desired 
result.  We can only assume that the user wants the interpolation with 
lowest frequency.  That is, perhaps the user gave commands to create the 
snow effect and that was his desired result.

Dan