Guide by Pvic.
This is really simple.
Basically this will make a value called xx and another called yy which define the center position of the sprite.
xx=x-sprite_get_xoffset(sprite_index)+(sprite_get_width(sprite_index)/2)
yy=y-sprite_get_yoffset(sprite_index)+(sprite_get_height(sprite_index)/2)
.
Example, in GMate, in par_enemy's destroy event's code you can change the part that creates the explosion effect to this
var xx;
xx=x-sprite_get_xoffset(sprite_index)+(sprite_get_width(sprite_index)/2)
var yy;
yy=y-sprite_get_yoffset(sprite_index)+(sprite_get_height(sprite_index)/2)
/* Create Explosion */
scr_dummy_effect(spr_enemy_explosion,0.2,xx,yy,1);
This will make that the explosion always comes from the middle of the sprite.