// Contour Color=ps_2_0
// http://forum.doom9.org/showthread.php?t=157634

// (C) 2011 Jan-Willem Krans (janwillem32 <at> hotmail.com)
// This file is part of Video pixel shader pack.
// This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
// This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

// contour color
// This shader can be run as a screen space pixel shader.
// This shader requires compiling with ps_2_0, but higher is better, see http://en.wikipedia.org/wiki/Pixel_shader to look up what PS version your video card supports.
// If possible, avoid compiling with the software emulation modes (ps_?_sw). Pixel shaders require a lot of processing power to run in real-time software mode.
// Use this shader to add a color contoured effect to an image.

sampler s0;
float2 c1 : register(c1);
#define sp(a, b, c) float4 a = tex2D(s0, tex+c1*float2(b, c));

float4 main(float2 tex : TEXCOORD0) : COLOR
{
	sp(s2, -1, -1) sp(s3, 0, -1) sp(s4, 1, -1) sp(s5, -1, 0) sp(s6, 1, 0) sp(s7, -1, 1) sp(s8, 0, 1) sp(s9, 1, 1)// sample surrounding pixels
	return smoothstep(.25, .125, abs(s2+s3+s4-s7-s8-s9)+abs(s2+s5+s7-s4-s6-s9)+abs(s2+s3+s5-s6-s8-s9)+abs(s3+s4+s6-s5-s7-s8));// color contour output
}