1. INTRODUCTION
Image compression is one of the most essential tasks in both signal processing and computer vision fields. Recently, with the rapid development of deep learning, learned image compression methods [1], [2], [3], [4] have drawn much attention and shown their excellent performance when compared to traditional frameworks [5], [6], [7]. Although numerous progress has been made in learned image compression, the recently proposed models still maintain high computation complexity, being not conducive to deployment on devices with limited resources, e.g., mobile phones and embedded devices that have extensive needs of image compression.