A pixel block is compressed by determining a reference set of multiple reference property values. A value index associated with a reference property value of the reference set is assigned to each pixel in the pixel block based on the original property value of the pixel. A prediction of the value index is provided based on the value index assigned to at least one neighboring pixel in the pixel block. A prediction error is calculated based on the value index assigned to a pixel and its value index prediction. The compressed pixel block includes encoded representations of the prediction errors and an encoded representation of the reference set.