The present disclosure provides picture encoding and decoding methods, picture encoding and decoding devices as well as a decoder and an encoder. The picture decoding method includes: parsing a video bitstream to obtain candidate reshaping parameters from a picture-layer and/or slice-layer data unit of the video bitstream, and determining a reshaping parameter used for reshaping a reconstructed picture according to the obtained candidate reshaping parameters; and reshaping the reconstructed picture by using the reshaping parameter. The reconstructed picture is a picture obtained by decoding the video bitstream before performing the reshaping. The picture-layer and/or slice-layer data unit includes at least one of the following data units: a picture-layer parameter set and/or a slice-layer parameter set different from a picture parameter set (PPS), a parameter data unit which are included in an access unit (AU) corresponding to the reconstructed picture, slice header and a system-layer picture parameter data unit.