Blending functions

• blend_add(src1, src2)
• blend_average(src1, src2)
• blend_color_burn(src1, src2)
• blend_color_dodge(src1, src2)
• blend_darken(src1, src2)
• blend_difference(src1, src2)
• blend_exclusion(src1, src2)
• blend_glow(src1, src2)
• blend_hard_light(src1, src2)
• blend_hard_max(src1, src2)
• blend_lighten(src1, src2)
• blend_linear_burn(src1, src2)
• blend_linear_dodge(src1, src2)
• blend_linear_light(src1, src2)
• blend_multiply(src1, src2)
• blend_negation(src1, src2)
• blend_normal(src1, src2)
• blend_overlay(src1, src2)
• blend_phoenix(src1, src2)
• blend_pin_light(src1, src2)
• blend_reflect(src1, src2)
• blend_screen(src1, src2)
• blend_soft_light(src1, src2)
• blend_sub(src1, src2)
• blend_vivid_lights(src1, src2)