Simple horizontal averaging programme enables shade correction for image analysis in psoriasis

Computer-assisted area measurement of skin lesions would be useful for the assessment of disease severity. Difficulties can be encountered, however, w hen lesions cannot simply be separated using the normal threshold tool of a n image analyser. Owing to body curvature, peripheral sites are usually sha dowed. To obtain a well-fitting curved line to account for body curvature-i nduced glare and shadow, we devised a simple C-programme for averaging neig hbouring pixels on the same horizontal line. An image was captured from a c olour slide to the image analysis system. C++ was used for programming. Exe cution of the averaging programme with the original image resulted in a bac kground brightness image file. When this was subtracted from the original i mage, the lesions were easily detected using the standard threshold tool an d the percentage of area involved was calculated. This method is sufficient ly accurate for the assessment of disease severity.