{
  "schemaVersion": 1,
  "authority": "Local display derivative of a retained public decorative frame. This is a guide packaging choice, not an observed production encoding.",
  "source": {
    "file": "assets/hero-background.png",
    "sha256": "a7b972150493fd6ba870860d7b6e95df0a7b3895f74c1a3e336a3750940dc8e8"
  },
  "losslessAlternative": {
    "file": "assets/hero-background.webp",
    "sha256": "645ee2fab43ca348ef7a449732bd579687e1e9ad4b62160771422cf062d18946",
    "bytes": 556892
  },
  "display": {
    "file": "assets/hero-background-display.webp",
    "sha256": "c4cd3a9fef0d23e51182f407b180157f6bd3888f0b6469e2209ae55adf8c46a5",
    "bytes": 331084,
    "dimensions": {
      "width": 1200,
      "height": 967
    }
  },
  "encoding": {
    "format": "WebP",
    "mode": "lossless WebP after near-lossless RGB preprocessing",
    "arguments": [
      "-lossless",
      "-near_lossless",
      "40",
      "-q",
      "100",
      "-m",
      "6",
      "-metadata",
      "none"
    ]
  },
  "comparison": {
    "method": "Exact byte differences after FFmpeg rgb24 decode; each channel is an unsigned 8-bit sample. RGB PSNR uses peak 255. No resizing or alignment.",
    "maximumAbsoluteRgbError": 4,
    "meanAbsoluteRgbError": 0.4098339652993221,
    "rootMeanSquaredRgbError": 0.9965287909346465,
    "ssim": {
      "R": 0.99521,
      "G": 0.99082,
      "B": 0.992852,
      "All": 0.99296
    },
    "ssimMethod": "FFmpeg ssim on decoded RGB bytes converted losslessly to planar gbrp; a single full-resolution frame.",
    "bytesSavedVsLosslessWebp": 225808,
    "percentSavedVsLosslessWebp": 40.547897976627425
  },
  "usage": "Only the overview hero uses and preloads this display derivative. The catalog specimen retains the original lossless WebP. Both original assets remain retrievable.",
  "measurementEvidence": {
    "file": "reference-data/evaluation-rounds/5/pending-hero-near-lossless/derivative-results.json",
    "sha256": "927058b0dc555bdf2d549118aa2ebd26ba1158b535ba56800558227b57fad685"
  },
  "limits": [
    "Decoded pixels are near-lossless, not identical to the original.",
    "The measurements describe encoding and visual differences; they do not establish browser loading performance.",
    "The still frame does not reproduce the source WebGL animation."
  ]
}