AlphaCallback Interface Reference

import"evg.idl";

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

Parameters

source_alpha	value of alpha of source color at the given pixel coordinate. Values are between 0 and 255
x	horizontal pixel coordinate, 0 meaning first column of raster surface
y	vertical pixel coordinate, 0 meaning first row of raster surface

Returns

the alpha value to use.

Warning

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