Implementation:Microsoft Playwright ColorUtils

Overview

ColorUtils provides color space conversion and perceptual color difference calculation functions used by Playwright's SSIM-based image comparison system.

Description

This module implements:

• blendWithWhite -- blends a color channel value with white using alpha
• rgb2gray -- converts RGB to grayscale using the ITU-R BT.601 formula
• colorDeltaE94 -- calculates the CIE94 perceptual color difference between two RGB colors
• Color space conversions -- sRGB to XYZ to CIELAB transformations needed for deltaE calculation

The CIE94 deltaE metric provides perceptually meaningful color differences:

• < 1.0: not perceptible by human eyes
• 1-2: perceptible through close observation
• 2-10: perceptible at a glance

Usage

Used by the SSIM image comparison algorithm to determine pixel-level color similarity.

Code Reference

Source Location

packages/playwright-core/src/server/utils/image_tools/colorUtils.ts (99 lines)

Function Signatures

export function blendWithWhite(c: number, a: number): number;
export function rgb2gray(r: number, g: number, b: number): number;
export function colorDeltaE94(rgb1: number[], rgb2: number[]): number;

Import

import { blendWithWhite, rgb2gray, colorDeltaE94 } from './server/utils/image_tools/colorUtils';

I/O Contract

blendWithWhite

• Input: color channel value (0-255), alpha (0-1)
• Output: blended color channel value

rgb2gray

• Input: r, g, b values (0-255)
• Output: grayscale value (0-255)

colorDeltaE94

• Input: two RGB arrays [r, g, b]
• Output: CIE94 deltaE value (0 = identical, ~1.0 = just noticeable difference)

Related Pages

• Microsoft_Playwright_ImageCompare -- SSIM comparison using color utilities
• Microsoft_Playwright_ImageChannel -- Image channel data structure
• Microsoft_Playwright_SsimStats -- SSIM statistical calculations