This book gathers selected papers presented at Sixth International Symposium on Signal and Image Processing (ISSIP 2025), organized by Rochester Institute of Technology Kosovo, Kosovo, during November 24 & 25, 2025. It presents fascinating, state-of-the-art research findings in the field of signal and image processing. It includes conference papers covering a wide range of signal processing applications involving filtering, encoding, classification, segmentation, clustering, feature extraction, denoising, watermarking, object recognition, reconstruction and fractal analysis.