BlendModeのVividLight | Codetter（こーどったー）

	screen 1, 256, 256
	title "base color : bottom layer"
	repeat 256
		y = cnt
		repeat 256
			x = cnt
			i = x
			color i, i, i
			pset x, y
		loop
	loop

	screen 2, 256, 256
	title "blend color : top layer"
	repeat 256
		y = cnt
		repeat 256
			x = cnt
			i = 255 -y
			color i, i, i
			pset x, y
		loop
	loop

	screen 0, 256, 256
	title "final output"
	repeat 256
		y = cnt
		repeat 256
			x = cnt

			base_i = double(x) /255.0
			blend_i = double( 255 -y ) /255.0
		#if 0
				// まちがい
			if ( blend_i < 0.5 ) {
				final_i = base_i / ( 1.0 - 2.0*blend_i )
			} else {
				final_i = 1.0 - ( 1.0-base_i ) / ( 2.0 * ( blend_i - 0.5 ) )
			}
		#else
				// ただしくはこっち
					// 0除算扱いになってしまうのでガードを適当に
			if ( blend_i < 0.5 ) {
				div = ( 2.0 * blend_i )
				if ( div > 0.0 ) {
					final_i = 1.0 - ( 1.0-base_i ) / div
				} else {
					final_i = 0.0
				}
			} else {
				div = ( 1.0 - 2.0*(blend_i-0.5) )
				if ( div > 0.0 ) {
					final_i = base_i / div
				} else {
					final_i = 1.0
				}
			}
		#endif
				// clamp
			final_i = limitf( final_i, 0.0 , 1.0 )

			i = int( 255.0 * final_i )
			color i, i, i
			pset x, y
		loop
	loop