Re: [Gimp-print-devel] Calculating actual Ink amounts from CMYK pipeline

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

On Mon, Jul 01, 2024 at 11:17:40AM -0400, Walker Blackwell wrote:
> There is some multiplication of numbers between the CMYK channels that 
> is happening in the system at some point. Does anyone know what this 
> multiplication is? If it’s a standard number/thing I can apply it to 
> my backwards math.

Coincidentally, I think I ran into what you're looking for last week. 
Have a look at do_gcr() in src/main/channels.c:

This is its main loop:

  for (i = 0; i < cg->width; i++)  // ie repeat for each pixel
    {
      unsigned k = output[0];
      if (k > 0)
	{
	  int kk = gcr_lookup[k];
	  int ck;
	  if (kk > k)
	    kk = k;
	  ck = k - kk;
	  output[0] = kk;
	  output[1] += ck * cg->cyan_balance;
	  output[2] += ck * cg->magenta_balance;
	  output[3] += ck * cg->yellow_balance;
	  nzx.nzl |= *(unsigned long long *) output;
	}
      output += cg->gcr_channels;
    }



 - Solomon
-- 
Solomon Peachy			      pizza at shaftnet dot org (email&xmpp)
                                      @pizza:shaftnet dot org   (matrix)
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