Various embodiments of a system and methods for decomposing an image into reflectance and shading components are described. An image decomposition module may represent an image as a product of the reflectance and shading components of the image. Data representing the image may be transformed into an image gradient containing both reflectance and shading component gradients. A normal vector perpendicular to the direction of the reflectance component gradient may be determined, based on a difference between the color channels of the image gradient. The image gradient may be modified according to the normal vector to eliminate the reflectance component gradient. The shading component gradient may be determined from the modified image gradient. The shading component gradient may be transformed into the shading component. The reflectance component may be determined by substituting the shading component into the representation of the image which is a product of the reflectance and shading components.