Retinex Enhancement (SSR) | 555Tools — Online Tools for FPGA & Algorithm Engineers

Image AlgorithmsTool Introduction

Single-Scale Retinex (Jobson, Rahman, Woodell 1997) separates illumination from reflectance in the log domain. SSR computes R = log(I+1) - log(G*I+1) where G* is Gaussian surround. Human perception is approximately logarithmic; illumination is low-frequency; reflectance = I/illumination, so subtraction in log domain removes illumination. Per-channel SSR for color images preserves color balance while enhancing local contrast.

Key Formula / Principle

R = log(I+1) - log(G*I+1)
out = gain * R + offset (or auto-stretch 2% clip)
Gaussian: separable, sigma 10~100

Data Processed Locally|All computations run in your browser. Images, formulas, state machine definitions, and any other input data are never sent to any server.

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