Declaration: TParticles.RemoveParticlePixel (ClassIdx: integer; px, py: integer): integer;
The function RemoveParticlePixel removes the pixel at position [px,py] from particles of class ClassIdx. The pixel coordinates are zero-based (valid range 0..SizeX-1 and 0..SizeY-1), the class number is 1-based (valid range 1..NClasses).

The specified pixel is removed from a particle. Depending on the position of the pixel there are three kinds of outcomes:

  • the specified pixel has no neighbors1) belonging to the specified particle class: the pixel is regarded to be a single-pixel particle, the particle is therefore removed
  • the specified pixel has one common edge with an existing particle of class ClassIdx: the pixel is removed from the particle (the particle shrinks by one pixel)
  • the pixel has two or more common edges: the pixel is removed and the remaining pixels are split in separate particles if required
The function returns the following error codes:
>0 ... everything is OK, the returned number is the particle index of the particle the pixel has been removed from
 0 ... the particle has been removed because it was a single-pixel particle
-1 ... invalid ClassIdx
-2 ... invalid px and/or py
-3 ... the pixel is not part of a particle, nothing has been changed

1) Neigboring pixels have to have at least one edge in common. If the two pixels touch each other only at the corner, they are not considered to be neighbors.

Hint: In order to access the particles currently loaded in the particle editor you can use the pre-declared global variable PEData.