Re: [Gimp-print-devel] Question about internal color conversion and gamma flow

[Solomon P. <pi...@sh...>]

On Wed, Sep 11, 2019 at 10:47:19PM -0400, Solomon Peachy wrote:
>  0 setup_page_dimensions_resolutions_etc
>  1 foreach ink_channels:
>  2  stp_channel_add(channel)  # CMY in this case
>  3 stp_color_init(256)        # ie 8bpp
>  4 stp_set_float_parameter("AppGammaScale", 1.0)
>  5 foreach input row:
>  6  src = stp_color_get_row()
>  7  dest = malloc()
>  8  memcpy(dest, src)
>  9 foreach printer_specific_curve  # optional
> 10  stp_set_curve_parameter(name, curve)

> (4) and (9-10) are interesting, leading to my first questions:
> 
>  * Does these calls have any effect, given that they both occur after 
>    stp_color_init() and/or the stp_color_get_row() calls?

To follow up to myself about (9-10), it looks like this call sequence 
was rearranged in commit f406f9715, way back in Sep 2006, and from what 
I can tell, making effectively into no-ops.

Here are the models affected by this goof:

 * Olympus P200, P300, P400
 * Canon Selphy series (all)
 * Sony UP-DP10

It seems prudent to re-arrange these into a more appropriate position, 
so the calls can actually do something now, but IMO the existing curves 
in there should be disabled until the AppGammaScale change can be 
evaluated more closely.

(On the other hand, only the Selphy series matters now, as media for the 
 others has been effectively unobtanium for the better part of a 
 decade.. when you can even find media it's so expensive that it's
 arguably cheaper to just replace the printer instead..)

 - Solomon
-- 
Solomon Peachy			       pizza at shaftnet dot org
High Springs, FL                          ^^ (email/xmpp) ^^
Quidquid latine dictum sit, altum videtur.