Effects of Improved Adaptive Gamma Correction Method on Wireless Capsule Endoscopy Images: Illumination Compensation and Edge Detection

Several methods for adjusting image contrast have been developed in the field of image processing for image enhancement. Illumination is one of the most significant factors affecting theappearance of an image. Improper illumination causes a variety of problems in practice and thus, it is necessary to compensate fornonuniform illumination. Wireless Capsule Endoscopy (WCE) images suffer from this problem too. We propose an improvedAdaptive Gamma Correction Method (AGCM) to compensate for nonuniform illumination in WCE color images.The experiments have shown that the proposed AGCM performs well in improving imagequality. The WCE images obtained with AGCM are also better than those obtained with histogram equalization and adaptive histogramequalization in terms of brightness constancy, overall visual rendition and contrast. The Peak Signal to Noise Ratio (PSNR) andContrast to Noise Ratio (CNR) values are also higher for AGCM than for other correction algorithms. Also, the differences betweenedge pixels and neighboring pixels in the WCE images are increased. We use a color variant of the canny operator for color edgedetection. By using this method, 65% of the borders are detected correctly, while the detection rate is 45% without using this method