In this article we propose a novel algorithm for lossless image compression based on 8x8 px block division and vector quantization. Each block is assigned to one of k classes and encoded using linear predictor assigned to a class (calculated using the Iterative Reweighted Least Squares (IRLS) algorithm). Several methods for initializing classes based on binary division of a set have been proposed. The main solution is a combination of these algorithms, in which class initialization procedure follows the pattern of a complete binary tree with k leaves. The proposed initialization method significantly reduced time required for the main vector quantization process. Proposed codec belongs to the time-asymmetric compression methods with a short decoding time and is characterized by high compression efficiency, offering on average a 7.22% lower bit average compared to JPEG-LS.