Documentation of the core library of GPAC
AlphaCallback Interface Reference


Public Member Functions

unsigned long on_alpha (unsigned long source_alpha, unsigned long x, unsigned long y)

Detailed Description

alpha callback type

Member Function Documentation

◆ on_alpha()

unsigned long AlphaCallback::on_alpha ( unsigned long  source_alpha,
unsigned long  x,
unsigned long  y 

alpha callback functions

source_alphavalue of alpha of source color at the given pixel coordinate. Values are between 0 and 255
xhorizontal pixel coordinate, 0 meaning first column of raster surface
yvertical pixel coordinate, 0 meaning first row of raster surface
the alpha value to use.
the return value is not checked for clamping, it should therefore be between 0 and 255
the coordinates are not relative to the centered mode of the surface, 0,0 is always the top-left corner