mix a shadow image with a cover image
[x colorMapNew]=eshadoix(matrix,coverImg,colorMap)
matrix :
matrix to calculate the shadow image
coverImg :
matrix for cover image
each value of this matrix is a row index of the colormap
colorMap :
colormap of coverImg
x :
mix shadow image matrix
colorMapNew :
colormap of x
special case of return parameters
if the return parameters are used then no output