colorcalibration also for manual wb

[kofa73]

Addresses #19873

• added a new checkbox, prepare data for color calibration to white balance temperature.c to explicitly control the late_correction flag in 'user' / 'manual' modes

  • the checkbox is only visible in such modes (late_correction is always off in 'camera reference' mode, always on in 'as-shot to reference')
  • if switching from 'camera reference' or 'as-shot to reference' to a 'user' mode, the checkbox is automatically ticked if color calibration is enabled

• replaced reference chr->as_shot with chr->wb_coeffs in highlights.c, colorin.c, opposed.c and segbased.c

• illuminants.h:

  • added a new illuminant, DT_ILLUMINANT_FROM_WB, plus handling in conditionals, similar to DT_ILLUMINANT_CAMERA, but relying on dev->chroma->wb_coeffs
  • find_temperature_from_raw_coeffs:
    • renamed to find_temperature_from_as_shot_coeffs
    • extracted the logic to find_temperature_from_wb_coeffs, to allow directly using coefficients from temperature.c, instead of always going through ratios relative to the D65 values
    • added param wb_coeffs to illuminant_to_xy for absolute coefficients from temperature.c; renamed param custom_wb to correction_ratios to express what it represents; passed to find_temperature_from_wb_coeffs in DT_ILLUMINANT_FROM_WB mode

• channelmixerrgb.c:

  • _dev_is_D65_chroma no longer needs as_shot multipliers in late_correction mode
  • renamed _get_white_balance_coeff to _get_d65_correction_ratios
  • wired up the calls to find_temperature_from_wb_coeffs to handle DT_ILLUMINANT_FROM_WB

  Draft for now, to allow discussion (and I haven't tested much, but wanted to make the changes visible to others; plus, I need to clean up some temp files)

[ralfbrown]

Did you intend to include cmixer_orig.c.txt in the PR?
And are the two .md files in the right place?

[kofa73]

Did you intend to include cmixer_orig.c.txt in the PR? And are the two .md files in the right place?

See the end of the description:

Draft for now, to allow discussion (and I haven't tested much, but wanted to make the changes visible to others; plus, I need to clean up some temp files)

[kofa73]

@ralfbrown : extra files removed, thank for your patience

[jenshannoschwalm]

A first complete code reading and remembering your comments before; generally i think this is a minor but very good improvement and will certainly help with some issues. Also it make the intention more clear and fixes some common misunderstandings.

I spotted some places like this:

dt_aligned_pixel_t correction;
  for_four_channels(k)
  {
    if(late && chr->wb_coeffs[k] > 1e-6f)
      correction[k] = chr->D65coeffs[k] / chr->wb_coeffs[k];
    else
      correction[k] = 1.0f;
  }

Could you explain if/why this is nevessary or is it just code-style?

[kofa73]

The key is the line:

correction[k] = chr->D65coeffs[k] / chr->wb_coeffs[k];

This used to be something like (below is one concrete example):

chr->D65coeffs[0] / chr->as_shot[0]

The new denominator comes from chr->wb_coeffs[k] (value set in temperature.c), which means it may be set using one of the sliders. The sliders may have a value of 0, so we must protect the division:

typedef struct dt_iop_temperature_params_t
{
  float red;     // $MIN: 0.0 $MAX: 8.0
  float green;   // $MIN: 0.0 $MAX: 8.0
  float blue;    // $MIN: 0.0 $MAX: 8.0
  float various; // $MIN: 0.0 $MAX: 8.0
  int preset;
} dt_iop_temperature_params_t;

One option would be to restrict the values to MIN: 0.1 or so, then we can avoid adding the protection everywhere.

If I misunderstood the question, please let me know.