无障碍调色板生成器

Who This Tool Is Designed For

Adequate colour contrast is critical for people with low vision, colour vision deficiency (CVD), and age-related visual conditions. The WHO estimates that at least 2.2 billion people worldwide have a near or distance vision impairment (WHO, 2019). Research by Owsley (2011) documents that contrast sensitivity declines significantly with age, making high-contrast design increasingly important for older adults. CVD affects approximately 300 million people globally (Colour Blind Awareness). Designers, developers, and brand teams use this tool to ensure their colour palettes meet WCAG minimum contrast requirements, protecting usability for all these populations.

WCAG 2.2 Contrast Requirements

• SC 1.4.3 (Contrast Minimum, Level AA): Normal text requires ≥ 4.5:1 contrast ratio. Large text (18pt+ or 14pt+ bold) requires ≥ 3:1.
• SC 1.4.6 (Enhanced Contrast, Level AAA): Normal text requires ≥ 7:1 contrast ratio. Large text requires ≥ 4.5:1.
• SC 1.4.11 (Non-text Contrast, Level AA): UI components and graphical objects require ≥ 3:1 contrast against adjacent colours.

Research Citations

• W3C (2023). "Web Content Accessibility Guidelines (WCAG) 2.2." w3.org/TR/WCAG22 · Defines the contrast ratio thresholds (4.5:1, 7:1, 3:1) and the relative luminance calculation algorithm used in this tool.
• Owsley, C. (2011). "Aging and vision." Vision Research, 51(13), 1610–1622. · Documents that contrast sensitivity declines significantly with age due to optical and neural changes, underscoring the importance of high-contrast design for ageing populations.
• World Health Organization (2019). World Report on Vision. · Establishes that at least 2.2 billion people worldwide have a vision impairment, with low vision and presbyopia being the most prevalent forms.
• Legge, G.E. (2007). Psychophysics of Reading in Normal and Low Vision. Lawrence Erlbaum Associates. · Foundational research on how contrast, font size, and spacing affect reading performance for people with low vision.
• Arditi, A. & Faye, E. (2004). "Monocular and binocular letter contrast sensitivity and letter acuity in a diverse ophthalmologic practice." Optometry and Vision Science, 81(4), 287–292. · Demonstrates the clinical significance of contrast sensitivity as a predictor of functional vision.

Algorithm

Relative luminance is calculated per WCAG 2.2 definition: sRGB channel values are linearised (removing gamma), then weighted (0.2126 R + 0.7152 G + 0.0722 B) per the ITU-R BT.709 standard. Contrast ratio = (L_lighter + 0.05) / (L_darker + 0.05).

Disclaimer

This tool calculates contrast ratios using the algorithm specified in WCAG 2.2. Meeting mathematical contrast thresholds is a necessary but not sufficient condition for readability · factors such as font weight, size, anti-aliasing, and display calibration also affect legibility. WCAG conformance requires evaluation across all success criteria, not contrast alone. This tool does not provide legal compliance advice. For formal accessibility audits, consult a qualified accessibility professional.