Article

PixelMath Blending Modes

by Enzo De Bernardini

The following examples show how to perform different blending operations between two images using PixelMath (see original PixInsight forum post). In the examples two images are blended: a vertical gradient (IMG1) and a horizontal gradient (IMG2). In the non-commutative operations indicated below, the operation is applied to IMG2 so IMG2 could be considered on a layer "above" IMG1.

The image IMG1 was created using this PixelMath expression:

max( 0,  X() )

A copy was then made and rotated 90° anti-clockwise with FastRotation, and the image IDs were edited (see how to change the ID).

Here are the resulting gradient images:

And here are some blending operations performed with them:

• Darken
  min( IMG1, IMG2 )
  
• Multiply
  IMG1 * IMG2
  
• Color Burn (non-commutative)
  ~(~IMG1 / IMG2)
  
• Linear Burn
  IMG1 + IMG2 - 1
  
• Lighten
  Max( IMG1, IMG2 )
  
• Screen
  ~(~IMG1 * ~IMG2)
  
• Color Dodge (non-commutative)
  IMG1 / ~IMG2
  
• Overlay (non-commutative)
  iif( IMG1 > 0.5, ~(~(2*(IMG1 - 0.5)) * ~IMG2), 2*IMG1*IMG2 )
  
• Soft Light (non-commutative)
  iif( IMG2 > 0.5, ~(~IMG1 * ~(IMG2 - 0.5)), IMG1*(IMG2 + 0.5) )
  
• Hard Light (non-commutative)
  iif( IMG2 > 0.5, ~(~IMG1 * ~(2*(IMG2 - 0.5))), 2*IMG1*IMG2 )
  
• Hard Mix
  iif( IMG1 < 1 - IMG2, 0, 1 )
  
• Vivid Light (non-commutative)
  iif( IMG2 > 0.5, ~(~IMG1/(IMG2 - 0.5)/2), IMG1/~(2*IMG2) )
  
• Linear Light (non-commutative)
  iif( IMG2 > 0.5, IMG1 + 2*(IMG2 - 0.5), IMG1 + 2*IMG2 - 1 )
  
• Pin Light (non-commutative)
  iif( IMG2 > 0.5, Max( IMG1, 2*(IMG2 - 0.5) ), Min( IMG1, 2*IMG2 ) )
  
• Difference
  IMG1 -- IMG2
  
• Exclusion
  0.5 - 2*(IMG1 - 0.5)*(IMG2 - 0.5)
  
• Subtract
  IMG1 - IMG2
  

PM_BlendingModes.xpsm
PixelMath instance icons collection.