A semiautomatic method for digital feature separation uses a trained sample selected by an operator using a software eye dropper tool or a similar region-of-interest tool to sample features of interest on a stored digital image of, for example, an electronic component such as pads, bumps or leads of the component. At least a part of the corrosion-resistive member is composed of a sintered silicon nitride body having an open porosity of not more than 5%. In the image forming apparatus, control of application amount of a fixing fluid to a recording medium is performed by the fixing fluid applying section based on the result obtained by the recording medium detection section for the recording medium such as thickness and material. Both parts have several transceivers that communicate with each other to ascertain the distance from one to the other.