{
  "context": "This criteria evaluates how well the engineer uses pixelmatch and pngjs to build a command-line image comparison tool with proper CLI features including argument parsing, performance timing, exit codes, and error handling for automation workflows.",
  "type": "weighted_checklist",
  "checklist": [
    {
      "name": "PNG Loading",
      "description": "Uses pngjs (PNG.sync.read or similar) to properly load PNG files from the file system into image buffers that can be passed to pixelmatch",
      "max_score": 15
    },
    {
      "name": "Pixelmatch Invocation",
      "description": "Correctly calls pixelmatch with img1.data, img2.data, output buffer (or null), width, height, and optional threshold parameter from command line",
      "max_score": 20
    },
    {
      "name": "Performance Timing",
      "description": "Implements performance timing using console.time/console.timeEnd or equivalent to measure and display comparison duration",
      "max_score": 15
    },
    {
      "name": "Dimension Validation",
      "description": "Detects when images have different dimensions by comparing width/height properties and reports this appropriately",
      "max_score": 10
    },
    {
      "name": "Error Percentage",
      "description": "Calculates and displays error percentage as (mismatched pixels / total pixels * 100) where total pixels = width * height",
      "max_score": 10
    },
    {
      "name": "Exit Code 0",
      "description": "Uses process.exit(0) or returns 0 when images match exactly (mismatched pixels === 0)",
      "max_score": 5
    },
    {
      "name": "Exit Code 64",
      "description": "Uses process.exit(64) for invalid arguments or file reading errors",
      "max_score": 5
    },
    {
      "name": "Exit Code 65",
      "description": "Uses process.exit(65) specifically when image dimensions don't match",
      "max_score": 5
    },
    {
      "name": "Exit Code 66",
      "description": "Uses process.exit(66) when images differ (mismatched pixels > 0)",
      "max_score": 5
    },
    {
      "name": "Optional Diff Output",
      "description": "Handles optional output-diff.png argument by creating output buffer when provided and writing PNG using pngjs (PNG.sync.write), or passing null to pixelmatch when not provided",
      "max_score": 10
    }
  ]
}