{
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    "# Backgrounds and RYB paint mixing\n",
    "\n",
    "White / transparent canvases and subtractive **RYB** mixing.  Concepts and\n",
    "figures: [color compositing](../guide/color_compositing.md).  CMYK is\n",
    "API-only in the combine-mode dropdown pending GUI polishing — available as\n",
    "`combine_mode='cmyk'`.\n",
    "\n",
    "![RYB paint mix vs additive RGB](../_static/compositing/paintmix_demo_light.png)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7d04b552",
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   "source": [
    "import multicolorfits as mcf"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "cbf52d54",
   "metadata": {},
   "source": [
    "## Backgrounds (preferred over `inverse=True`)\n",
    "\n",
    "Classic `combine_multicolor(..., inverse=True)` plus `hex_complement()` was the v2\n",
    "route to a light canvas.  Prefer an explicit background:\n",
    "\n",
    "```python\n",
    "s.compose.combine_background = 'white'\n",
    "s.compose.combine_background = 'transparent'\n",
    "s.compose.combine_background = '#F5F0E6'   # custom\n",
    "s.compose.facecolor = 'none'              # transparent figure canvas when saving\n",
    "```\n",
    "\n",
    "In the browser GUI the Compositing tab exposes the same choices (and a\n",
    "side-by-side montage of white / RYB / transparent):\n",
    "[gui walkthrough](gui_web_walkthrough.md)."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "50d8bd1c",
   "metadata": {},
   "source": [
    "## RYB (paint-like subtractive)\n",
    "\n",
    "```python\n",
    "s.compose.combine_mode = 'ryb'\n",
    "# blend is ignored for RYB/CMYK — chroma mixes subtractively\n",
    "rgb = s.render_combined()\n",
    "```\n",
    "\n",
    "Or with the low-level helpers:\n",
    "\n",
    "```python\n",
    "rgb = mcf.combine_colorized_layers(colorized_list, mode='ryb', gamma=2.2)\n",
    "```\n",
    "\n",
    "Yellow + blue → green on the paint wheel (not cyan-ish white as in additive\n",
    "RGB).  That is intentional.  For additive Lab mixing that keeps hues distinct\n",
    "under bright overlaps, use `combine_mode='lab'` + `combine_blend='screen'`."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e900a837",
   "metadata": {},
   "source": [
    "## When to use what\n",
    "\n",
    "| Goal | Setting |\n",
    "|------|---------|\n",
    "| General science color composite | Lab / screen |\n",
    "| Classic channel sum | RGB (`combine_multicolor`) |\n",
    "| Paint / ink aesthetic | RYB |\n",
    "| Print-ink invert feel | CMYK (API) |\n",
    "| Slides with irregular outline | transparent background + cutout export |"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "cc2fe807",
   "metadata": {},
   "outputs": [],
   "source": [
    "print('Backgrounds + RYB — see docs/guide/color_compositing.md')"
   ]
  }
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