A method for determining encoding parameters for encoding indexes of a block of indexes used for encoding a coding unit of an image according to a palette, each index being related to one of the pixels forming the coding unit, the palette comprising a set of indexes associated to pixel values. The method comprises: generating each index of the block of indexes related to the coding unit from the palette based on corresponding encoding parameters, and if indexes of the block of indexes cannot be generated from the palette for at least one pixels of the coding unit, generating index values corresponding to escape values for replacing said indexes of the block of indexes which cannot be generated, wherein encoding parameters corresponding to an index are determined according to the spatial neighborhood of said pixel regarding to an encoding order.