c = color of the brush;
o_c = original brush color;
c_v = variancy in the brush color;
o = opacity;
o_b_s = original brush size;
b_s = brush size;
s_v = brush size variation;
i_g = index of the group (each scratch is a group);
i_s = self index in the group;
i_a = absolue index;
x = x position;
y = y position.