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al_premul_rgba_f(3)	    Library Functions Manual	     al_premul_rgba_f(3)

NAME
     al_premul_rgba_f - Allegro 5 API

SYNOPSIS
	    #include <allegro5/allegro.h>

	    ALLEGRO_COLOR al_premul_rgba_f(float r, float g, float b, float a)

DESCRIPTION
     This is a shortcut for al_map_rgba_f(3)(r * a, g * a, b * a, a).

     By  default  Allegro  uses pre-multiplied alpha for transparent blending of
     bitmaps and primitives (see al_load_bitmap_flags(3)  for  a  discussion  of
     that  feature).   This means that if you want to tint a bitmap or primitive
     to be transparent you need to multiply the color components  by  the  alpha
     components when you pass them to this function.  For example:

	    float r = 1;
	    float g = 0;
	    float b = 0;
	    float a = 0.5;
	    ALLEGRO_COLOR c = al_premul_rgba_f(r, g, b, a);
	    /* Draw the bitmap tinted red and half-transparent. */
	    al_draw_tinted_bitmap(bmp, c, 0, 0, 0);

     This function can be called before Allegro is initialized.

SINCE
     5.1.12

SEE ALSO
     al_map_rgba_f(3), al_premul_rgba(3)

Allegro reference manual				     al_premul_rgba_f(3)

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