A method based on the magneto-optical Kerr effect is demonstrated, which makes it possible to quantitatively determine spatial dependences of the directions of an in-plane component of inhomogeneous magnetic field visualized by soft nanocrystalline films. The method consists in obtaining magneto-optical images of micromagnetic structures that are formed under the influence of an inhomogeneous field. Images in the longitudinal and transverse sensitivity of the Kerr effect are used to calculate the angular dependence of the directions of the unit vectors of this field under the assumption that the components of the field are proportional to the brightness of magneto-optical images. The field direction maps obtained in this way agree with model calculations for our magnets.