This book constitutes the refereed proceedings of the 20th Chinese Conference on Image and Graphics Technologies and Applications, IGTA 2025, held in Beijing, China, during August 9-10, 2025. The 25 full papers included in this book were carefully reviewed and selected from 103 submissions. The papers focus on image processing, computer graphics, and related topics, including but not limited to image analysis and understanding, computer vision and pattern recognition, data mining, virtual reality and augmented reality, and image technology applications.