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README.md

diffimg

diffimg is a command-line tool for comparing two images using the imagediff library's tolerance logic. It supports various image formats and allows for fine-grained control over comparison thresholds via JSON configuration and optional masking.

Usage

diffimg [options] <reference> <candidate>

Arguments

  • <reference>: Path to the golden/expected image.
  • <candidate>: Path to the test/actual image.

Options

  • --config <path>: Path to a JSON configuration file defining comparison thresholds.
  • --mask <path>: Path to a grayscale mask image (0 = ignore, >0 = compare).
  • --diff <path>: Path to output a visual difference image (unmasked absolute difference).
  • --help, -h: Print help message.

Output

The tool outputs a JSON object to stdout containing the comparison results:

{ "status": 0, "passed": true, "failingPixelCount": 0, "maxDiffFound": [0.0, 0.0, 0.0, 0.0] }

Status Codes

  • 0: PASSED (Images are considered the same within tolerance)
  • 1: SIZE_MISMATCH (Images have different dimensions)
  • 2: PIXEL_DIFFERENCE (Images differ beyond the allowed tolerance)

Configuration Format

The optional JSON configuration follows the imagediff schema:

{ "mode": "LEAF", "maxAbsDiff": 0.01, "maxFailingPixelsFraction": 0.05 }

Dependencies

  • libs/imagediff: Comparison logic.
  • libs/imageio: Primary image decoding (PNG, HDR, EXR).
  • libs/imageio-lite: Fallback decoding (TIFF).