{
  "run_date": "2026-10-05",
  "python": "3.9.6",
  "platform": "Darwin",
  "standard": "WCAG 2.2",
  "scope": "opaque 8-bit #RRGGBB sRGB pairs; arithmetic only",
  "formula_source": "https://www.w3.org/WAI/WCAG22/Techniques/general/G18",
  "cases": [
    {
      "case": "black",
      "foreground": "#000000",
      "background": "#FFFFFF",
      "foreground_luminance": 0.0,
      "ratio_raw": 21.0,
      "ratio_display_2dp": "21.00",
      "meets_4_5": true,
      "meets_3_0": true
    },
    {
      "case": "gray_118",
      "foreground": "#767676",
      "background": "#FFFFFF",
      "foreground_luminance": 0.18116424424986022,
      "ratio_raw": 4.542224959605253,
      "ratio_display_2dp": "4.54",
      "meets_4_5": true,
      "meets_3_0": true
    },
    {
      "case": "gray_119",
      "foreground": "#777777",
      "background": "#FFFFFF",
      "foreground_luminance": 0.184474994500441,
      "ratio_raw": 4.478089453577214,
      "ratio_display_2dp": "4.48",
      "meets_4_5": false,
      "meets_3_0": true
    },
    {
      "case": "rounding_trap",
      "foreground": "#707972",
      "background": "#FFFFFF",
      "foreground_luminance": 0.18334393945078467,
      "ratio_raw": 4.49979546274635,
      "ratio_display_2dp": "4.50",
      "meets_4_5": false,
      "meets_3_0": true
    },
    {
      "case": "gray_136",
      "foreground": "#888888",
      "background": "#FFFFFF",
      "foreground_luminance": 0.24620132670783546,
      "ratio_raw": 3.5448862152994005,
      "ratio_display_2dp": "3.54",
      "meets_4_5": false,
      "meets_3_0": true
    },
    {
      "case": "red",
      "foreground": "#FF0000",
      "background": "#FFFFFF",
      "foreground_luminance": 0.2126,
      "ratio_raw": 3.9984767707539985,
      "ratio_display_2dp": "4.00",
      "meets_4_5": false,
      "meets_3_0": true
    },
    {
      "case": "green",
      "foreground": "#00FF00",
      "background": "#FFFFFF",
      "foreground_luminance": 0.7152,
      "ratio_raw": 1.3721902770517513,
      "ratio_display_2dp": "1.37",
      "meets_4_5": false,
      "meets_3_0": false
    },
    {
      "case": "blue",
      "foreground": "#0000FF",
      "background": "#FFFFFF",
      "foreground_luminance": 0.0722,
      "ratio_raw": 8.592471358428805,
      "ratio_display_2dp": "8.59",
      "meets_4_5": true,
      "meets_3_0": true
    }
  ],
  "boundary_checks": [
    "exact 4.5 accepted",
    "4.499 rejected",
    "next float below 4.5 rejected",
    "identical colors give 1",
    "black and white give 21",
    "foreground/background symmetry",
    "both transfer-function branches",
    "256 gray levels decrease monotonically",
    "lowercase hex accepted",
    "malformed or unsupported hex rejected",
    "alpha input rejected",
    "Display P3 input rejected",
    "rounded-display trap reproduced",
    "RGB mean counterexample",
    "encoded-channel counterexample"
  ],
  "rgb_mean_counterexample": {
    "colors": [
      "#FF0000",
      "#00FF00",
      "#0000FF"
    ],
    "means": [
      85.0,
      85.0,
      85.0
    ]
  },
  "encoding_counterexample": {
    "color": "#808080",
    "normalized_channel": 0.5019607843137255,
    "relative_luminance": 0.21586050011389923,
    "correct_ratio_on_white": 3.9494396480491156,
    "incorrect_ratio_using_encoded_channel": 1.9023090586145648
  }
}