1. A method performed by a computational device as part of transforming a source digital image into a digital object in a target digital image, the source digital image and the target digital image each comprising a plurality of pixels; the method comprising: receiving and storing the source digital image in memory; receiving at a user interface an indication of an effect to be applied to said source digital image; obtaining a set of parameters based on the indication of the effect; obtaining a value defining a width of an area that borders at least one boundary of the digital object in the target digital image; the width of the area being uniform along the at least one boundary of the digital object; for a pixel coordinate (x t , y t ) of the target digital image that is within the area that borders the at least one boundary of the digital object, computing, using the pixel coordinate (x t , y t ) of the target digital image and at least some of the parameters, a corresponding source pixel coordinate (x s , y s ) that is within another area bordering the source digital image, said another area having a width that is non-uniform along a boundary of the source digital image; computing an alpha channel value defining semi-transparency of a pixel associated with the pixel coordinate (x t , y t ) of the target digital image, the alpha channel value computed as a function of: (i) a distance between the corresponding source pixel coordinate (x s , y s ) and the boundary of the source digital image, and (ii) the width of said another area at the location of the corresponding source pixel coordinate (x s , y s ).