Incoherent digital holography (IDH) enables the recording of holograms with incoherent light. However, there is unnatural bokeh with ringing on reconstructed 2D images, owing to the diffraction calculation based on the coherent nature of the light. Thus, we propose a transformation method that converts it into incoherent bokeh. This proposed method can generate 2D images without ringing from recorded holograms through a virtual incoherent imaging system, while focusing on the non-linearity problem of reconstruction distances in IDH. Flexible depth-of-field control is also made possible by the judicious selection of parameters in this method. A proof-of-principle demonstration verifies its feasibility.