oh, I made a mistake. Thanks a lot! In your mail: >From: "William Skaggs" <weskaggs@xxxxxxxxxxxxxxxxxxx> >Reply-To: <weskaggs@xxxxxxxxxxxxxxxxxxx> >To: <gimp-developer@xxxxxxxxxxxxxxxxxxxxxx>, bear <xgl99@xxxxxxxxxxxxxxxxxxxxx> >Subject: Re: [Gimp-developer] how layers actually get merged? > > > Bear wrote: > > Assume there are four layers, all of which are in Normal mode and grayscale. > > for a specific pixel in each layer, > > Their intensity and alpha values(mapped to [0,1]) are > > i1,a1 > > i2,a2 > > i3,a3 > > i4(background) > > > > the merged intensity is ((i1*a1+i2*(1-a1))*a2+i3*(1-a2))*a3+i4*(1-a3) > > am I correct? Thanks! > > I hope not. The proper expression should be > > a1*i1 + (1-a1) * (a2*i2 + (1-a2) * (a3*i3 + (1-a3) * i4)). > > That is, you have the expression reversed. With your expression, the > background could show through even with opaque layers above it. > >
