Basically:

let A = original image pixel color
let B = filtered image pixel color
redPart(B) = cos(redPart(A)) * redPart(A)
greenPart(B) = cos(greenPart(A)) * greenPart(A)
bluePart(B) = cos(bluePart(A)) * bluePart(A)
Repeat for every image pixel color of A.