Module viewing 

Viewing condition modeling for perceptual quality assessment.

This module provides the ViewingCondition type which models how an image will be viewed, affecting perceptual quality thresholds.

Key Concepts

• acuity_ppd: The viewer’s visual acuity in pixels per degree. This is determined by the display’s pixel density and viewing distance.
• browser_dppx: The browser/OS device pixel ratio (e.g., 2.0 for retina).
• image_intrinsic_dppx: The image’s intrinsic pixels per CSS pixel (for srcset).
• ppd: The effective pixels per degree for this specific image viewing.

Simulation Modes

When simulating viewing conditions for metric calculation, there are two approaches:

• SimulationMode::Accurate: Simulate browser behavior exactly, including upscaling undersized images. This matches real-world viewing but introduces resampling artifacts.

• SimulationMode::DownsampleOnly: Never upsample images. For undersized images, adjust the effective PPD instead. This avoids simulation artifacts but requires metric threshold adjustment.

Modules

presets

Pre-defined viewing condition presets for common scenarios.

Structs

SimulationParams

Parameters for viewing simulation.

ViewingCondition

Viewing condition for perceptual quality assessment.

Enums

SimulationMode

How to handle image scaling during viewing simulation.

Constants

REFERENCE_PPD

Reference PPD for metric threshold normalization.