• Adobe Photoshop

  The linear algebra behind transfer modes. . .

  Posted by Lazlo Hollyfeld on July 7, 2005 at 6:18 pm

  Hi There!

  I’m curious if anybody knows the actual mathematical calculations that go on between layers when altering transfer modes. For example, I understand “Multiply”. . .every pixel on the first layer is multiplied with every pixel on the layer below it. But what about Overlay? Hard Light, etc.? Is there documentation of this found anywhere? On the web? In books?

  Thanks for your help!

  Arie

  Richard Harrington replied 20 years, 12 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Lazlo Hollyfeld

  July 7, 2005 at 8:23 pm

  Found some just Googling around, but if you know where I can get the rest, please do let me know. Here is what I found, where A is the top layer and B is the layer directly below A.

  Multiply: A*B
  Screen: A+B-A*B or 1-(1-A)*(1-B)
  Overlay: (B>.5)? 2*(A+B-A*B)-1 : 2*A*B
  HardLight: (A>.5)? 2*(A+B-A*B)-1 : 2*A*B
  Darken: min(A,B)
  Lighten: max(A,B)
  Difference: abs(A-B)

  Arie
• 

  Richard Harrington

  July 11, 2005 at 4:11 am

  Look for Channel Chops by Burt Monroy (out of print)

  or Katrin Eisman has a new book “Understanding Channels” (I think is title)

  Richard M. Harrington, PMP

  Author: Photoshop CS for Nonlinear Editors
  Co-Author Final Cut Pro on the Spot, After Effects on the Spot, Broadcast Graphics on the Spot, and After Effects @ Work
  Check out the new DVD: Photoshop CS: Essentials for Digital Video from http://www.photoshopforvideo.com

  edit – produce – direct –

Reply to this Discussion! Login or Sign Up