// PUBLIC DOMAIN CRT STYLED SCAN-LINE SHADER
//
//   by Timothy Lottes
//
// This is more along the style of a really good CGA arcade monitor.
// With RGB inputs instead of NTSC.
// The shadow mask example has the mask rotated 90 degrees for less chromatic aberration.
//
// Left it unoptimized to show the theory behind the algorithm.
//
// It is an example what I personally would want as a display option for pixel art games.
// Please take and use, change, or whatever.

// Parameter lines go here:
#pragma parameter hardScan "hardScan" -8.0 -20.0 0.0 1.0
#pragma parameter hardPix "hardPix" -3.0 -20.0 0.0 1.0
#pragma parameter warpX "warpX" 0.031 0.0 0.125 0.01
#pragma parameter warpY "warpY" 0.041 0.0 0.125 0.01
#pragma parameter maskDark "maskDark" 0.5 0.0 2.0 0.1
#pragma parameter maskLight "maskLight" 1.5 0.0 2.0 0.1
#pragma parameter scaleInLinearGamma "scaleInLinearGamma" 1.0 0.0 1.0 1.0
#pragma parameter shadowMask "shadowMask" 3.0 0.0 4.0 1.0
#pragma parameter brightBoost "brightness boost" 1.0 0.0 2.0 0.05
#pragma parameter hardBloomPix "bloom-x soft" -1.5 -2.0 -0.5 0.1
#pragma parameter hardBloomScan "bloom-y soft" -2.0 -4.0 -1.0 0.1
#pragma parameter bloomAmount "bloom amount" 0.15 0.0 1.0 0.05
#pragma parameter shape "filter kernel shape" 2.0 0.0 10.0 0.05

#if defined(VERTEX)

#if __VERSION__ >= 130
#define COMPAT_VARYING out
#define COMPAT_ATTRIBUTE in
#define COMPAT_TEXTURE texture
#else
#define COMPAT_VARYING varying
#define COMPAT_ATTRIBUTE attribute
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

COMPAT_ATTRIBUTE vec4 VertexCoord;
COMPAT_ATTRIBUTE vec4 COLOR;
COMPAT_ATTRIBUTE vec4 TexCoord;
COMPAT_VARYING vec4 COL0;
COMPAT_VARYING vec4 TEX0;

uniform COMPAT_PRECISION vec2 rubyTextureSize;
uniform COMPAT_PRECISION vec2 rubyInputSize;

COMPAT_ATTRIBUTE vec4 a_position;
COMPAT_VARYING vec2 v_texCoord;

void main()
{
	gl_Position = a_position;
	v_texCoord = vec2(a_position.x+1.0,1.0-a_position.y)/2.0*rubyInputSize/rubyTextureSize;
}

#elif defined(FRAGMENT)

#if __VERSION__ >= 130
#define COMPAT_VARYING in
#define COMPAT_TEXTURE texture
out vec4 FragColor;
#else
#define COMPAT_VARYING varying
#define FragColor gl_FragColor
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

uniform COMPAT_PRECISION vec2 rubyTextureSize;
uniform COMPAT_PRECISION vec2 rubyInputSize;
uniform COMPAT_PRECISION vec2 rubyOutputSize;

uniform COMPAT_PRECISION sampler2D rubyTexture;
COMPAT_VARYING vec2 v_texCoord;

// fragment compatibility #defines
#define Source rubyTexture
#define vTexCoord v_texCoord.xy

#define SourceSize vec4(rubyTextureSize, 1.0 / rubyTextureSize) //either TextureSize or InputSize
#define outsize vec4(rubyOutputSize, 1.0 / rubyOutputSize)

#ifdef PARAMETER_UNIFORM
// All parameter floats need to have COMPAT_PRECISION in front of them
uniform COMPAT_PRECISION float hardScan;
uniform COMPAT_PRECISION float hardPix;
uniform COMPAT_PRECISION float warpX;
uniform COMPAT_PRECISION float warpY;
uniform COMPAT_PRECISION float maskDark;
uniform COMPAT_PRECISION float maskLight;
uniform COMPAT_PRECISION float scaleInLinearGamma;
uniform COMPAT_PRECISION float shadowMask;
uniform COMPAT_PRECISION float brightBoost;
uniform COMPAT_PRECISION float hardBloomPix;
uniform COMPAT_PRECISION float hardBloomScan;
uniform COMPAT_PRECISION float bloomAmount;
uniform COMPAT_PRECISION float shape;
#else
#define hardScan -8.0
#define hardPix -3.0
#define warpX 0.031
#define warpY 0.041
#define maskDark 0.5
#define maskLight 1.5
#define scaleInLinearGamma 1.0
#define shadowMask 3.0
#define brightBoost 1.0
#define hardBloomPix -1.5
#define hardBloomScan -2.0
#define bloomAmount 0.15
#define shape 2.0
#endif

//Uncomment to reduce instructions with simpler linearization
//(fixes HD3000 Sandy Bridge IGP)
//#define SIMPLE_LINEAR_GAMMA
#define DO_BLOOM

// ------------- //

// sRGB to Linear.
// Assuming using sRGB typed textures this should not be needed.
#ifdef SIMPLE_LINEAR_GAMMA
float ToLinear1(float c)
{
	return c;
}
vec3 ToLinear(vec3 c)
{
	return c;
}
vec3 ToSrgb(vec3 c)
{
	return pow(c, vec3(1.0 / 2.2));
}
#else
float ToLinear1(float c)
{
	if (scaleInLinearGamma == 0.)
		return c;

	return(c<=0.04045) ? c/12.92 : pow((c + 0.055)/1.055, 2.4);
}

vec3 ToLinear(vec3 c)
{
	if (scaleInLinearGamma==0.)
		return c;

	return vec3(ToLinear1(c.r), ToLinear1(c.g), ToLinear1(c.b));
}

// Linear to sRGB.
// Assuming using sRGB typed textures this should not be needed.
float ToSrgb1(float c)
{
	if (scaleInLinearGamma == 0.)
		return c;

	return(c<0.0031308 ? c*12.92 : 1.055*pow(c, 0.41666) - 0.055);
}

vec3 ToSrgb(vec3 c)
{
	if (scaleInLinearGamma == 0.)
		return c;

	return vec3(ToSrgb1(c.r), ToSrgb1(c.g), ToSrgb1(c.b));
}
#endif

// Nearest emulated sample given floating point position and texel offset.
// Also zero's off screen.
vec3 Fetch(vec2 pos,vec2 off){
  pos=(floor(pos*SourceSize.xy+off)+vec2(0.5,0.5))/SourceSize.xy;
#ifdef SIMPLE_LINEAR_GAMMA
  return ToLinear(brightBoost * pow(COMPAT_TEXTURE(Source,pos.xy).rgb, vec3(2.2)));
#else
  return ToLinear(brightBoost * COMPAT_TEXTURE(Source,pos.xy).rgb);
#endif
}

// Distance in emulated pixels to nearest texel.
vec2 Dist(vec2 pos)
{
	pos = pos*SourceSize.xy;

	return -((pos - floor(pos)) - vec2(0.5));
}

// 1D Gaussian.
float Gaus(float pos, float scale)
{
	return exp2(scale*pow(abs(pos), shape));
}

// 3-tap Gaussian filter along horz line.
vec3 Horz3(vec2 pos, float off)
{
	vec3 b    = Fetch(pos, vec2(-1.0, off));
	vec3 c    = Fetch(pos, vec2( 0.0, off));
	vec3 d    = Fetch(pos, vec2( 1.0, off));
	float dst = Dist(pos).x;

	// Convert distance to weight.
	float scale = hardPix;
	float wb = Gaus(dst-1.0,scale);
	float wc = Gaus(dst+0.0,scale);
	float wd = Gaus(dst+1.0,scale);

	// Return filtered sample.
	return (b*wb+c*wc+d*wd)/(wb+wc+wd);
}

// 5-tap Gaussian filter along horz line.
vec3 Horz5(vec2 pos,float off){
	vec3 a = Fetch(pos,vec2(-2.0, off));
	vec3 b = Fetch(pos,vec2(-1.0, off));
	vec3 c = Fetch(pos,vec2( 0.0, off));
	vec3 d = Fetch(pos,vec2( 1.0, off));
	vec3 e = Fetch(pos,vec2( 2.0, off));

	float dst = Dist(pos).x;
	// Convert distance to weight.
	float scale = hardPix;
	float wa = Gaus(dst - 2.0, scale);
	float wb = Gaus(dst - 1.0, scale);
	float wc = Gaus(dst + 0.0, scale);
	float wd = Gaus(dst + 1.0, scale);
	float we = Gaus(dst + 2.0, scale);

	// Return filtered sample.
	return (a*wa+b*wb+c*wc+d*wd+e*we)/(wa+wb+wc+wd+we);
}

// 7-tap Gaussian filter along horz line.
vec3 Horz7(vec2 pos,float off)
{
	vec3 a = Fetch(pos, vec2(-3.0, off));
	vec3 b = Fetch(pos, vec2(-2.0, off));
	vec3 c = Fetch(pos, vec2(-1.0, off));
	vec3 d = Fetch(pos, vec2( 0.0, off));
	vec3 e = Fetch(pos, vec2( 1.0, off));
	vec3 f = Fetch(pos, vec2( 2.0, off));
	vec3 g = Fetch(pos, vec2( 3.0, off));

	float dst = Dist(pos).x;
	// Convert distance to weight.
	float scale = hardBloomPix;
	float wa = Gaus(dst - 3.0, scale);
	float wb = Gaus(dst - 2.0, scale);
	float wc = Gaus(dst - 1.0, scale);
	float wd = Gaus(dst + 0.0, scale);
	float we = Gaus(dst + 1.0, scale);
	float wf = Gaus(dst + 2.0, scale);
	float wg = Gaus(dst + 3.0, scale);

	// Return filtered sample.
	return (a*wa+b*wb+c*wc+d*wd+e*we+f*wf+g*wg)/(wa+wb+wc+wd+we+wf+wg);
}

// Return scanline weight.
float Scan(vec2 pos, float off)
{
	float dst = Dist(pos).y;

	return Gaus(dst + off, hardScan);
}

// Return scanline weight for bloom.
float BloomScan(vec2 pos, float off)
{
	float dst = Dist(pos).y;

	return Gaus(dst + off, hardBloomScan);
}

// Allow nearest three lines to effect pixel.
vec3 Tri(vec2 pos)
{
	vec3 a = Horz3(pos,-1.0);
	vec3 b = Horz5(pos, 0.0);
	vec3 c = Horz3(pos, 1.0);

	float wa = Scan(pos,-1.0);
	float wb = Scan(pos, 0.0);
	float wc = Scan(pos, 1.0);

	return a*wa + b*wb + c*wc;
}

// Small bloom.
vec3 Bloom(vec2 pos)
{
	vec3 a = Horz5(pos,-2.0);
	vec3 b = Horz7(pos,-1.0);
	vec3 c = Horz7(pos, 0.0);
	vec3 d = Horz7(pos, 1.0);
	vec3 e = Horz5(pos, 2.0);

	float wa = BloomScan(pos,-2.0);
	float wb = BloomScan(pos,-1.0);
	float wc = BloomScan(pos, 0.0);
	float wd = BloomScan(pos, 1.0);
	float we = BloomScan(pos, 2.0);

	return a*wa+b*wb+c*wc+d*wd+e*we;
}

// Distortion of scanlines, and end of screen alpha.
vec2 Warp(vec2 pos)
{
	pos  = pos*2.0-1.0;
	pos *= vec2(1.0 + (pos.y*pos.y)*warpX, 1.0 + (pos.x*pos.x)*warpY);

	return pos*0.5 + 0.5;
}

// Shadow mask.
vec3 Mask(vec2 pos)
{
	vec3 mask = vec3(maskDark, maskDark, maskDark);

	// Very compressed TV style shadow mask.
	if (shadowMask == 1.0)
	{
		float line = maskLight;
		float odd = 0.0;

		if (fract(pos.x*0.166666666) < 0.5) odd = 1.0;
		if (fract((pos.y + odd) * 0.5) < 0.5) line = maskDark;

		pos.x = fract(pos.x*0.333333333);

		if      (pos.x < 0.333) mask.r = maskLight;
		else if (pos.x < 0.666) mask.g = maskLight;
		else                    mask.b = maskLight;
		mask*=line;
	}

	// Aperture-grille.
	else if (shadowMask == 2.0)
	{
		pos.x = fract(pos.x*0.333333333);

		if      (pos.x < 0.333) mask.r = maskLight;
		else if (pos.x < 0.666) mask.g = maskLight;
		else                    mask.b = maskLight;
	}

	// Stretched VGA style shadow mask (same as prior shaders).
	else if (shadowMask == 3.0)
	{
		pos.x += pos.y*3.0;
		pos.x  = fract(pos.x*0.166666666);

		if      (pos.x < 0.333) mask.r = maskLight;
		else if (pos.x < 0.666) mask.g = maskLight;
		else                    mask.b = maskLight;
	}

	// VGA style shadow mask.
	else if (shadowMask == 4.0)
	{
		pos.xy  = floor(pos.xy*vec2(1.0, 0.5));
		pos.x  += pos.y*3.0;
		pos.x   = fract(pos.x*0.166666666);

		if      (pos.x < 0.333) mask.r = maskLight;
		else if (pos.x < 0.666) mask.g = maskLight;
		else                    mask.b = maskLight;
	}

	return mask;
}

void main()
{
	vec2 pos = Warp(v_texCoord.xy*(rubyTextureSize.xy/rubyInputSize.xy))*(rubyInputSize.xy/rubyTextureSize.xy);
	vec3 outColor = Tri(pos);

#ifdef DO_BLOOM
	//Add Bloom
	outColor.rgb += Bloom(pos)*bloomAmount;
#endif

	if (shadowMask > 0.0)
		outColor.rgb *= Mask(gl_FragCoord.xy * 1.000001);

#ifdef GL_ES    /* TODO/FIXME - hacky clamp fix */
	vec2 bordertest = (pos);
	if ( bordertest.x > 0.0001 && bordertest.x < 0.9999 && bordertest.y > 0.0001 && bordertest.y < 0.9999)
		outColor.rgb = outColor.rgb;
	else
		outColor.rgb = vec3(0.0);
#endif
	FragColor = vec4(ToSrgb(outColor.rgb), 1.0);
}
#endif