// CRT-Easymode
// 移植自 https://github.com/libretro/common-shaders/blob/master/crt/shaders/crt-easymode.cg

/*
	CRT Shader by EasyMode
	License: GPL

	A flat CRT shader ideally for 1080p or higher displays.

	Recommended Settings:

	Video
	- Aspect Ratio: 4:3
	- Integer Scale: Off

	Shader
	- Filter: Nearest
	- Scale: Don't Care

	Example RGB Mask Parameter Settings:

	Aperture Grille (Default)
	- Dot Width: 1
	- Dot Height: 1
	- Stagger: 0

	Lottes' Shadow Mask
	- Dot Width: 2
	- Dot Height: 1
	- Stagger: 3
*/

//!MAGPIE EFFECT
//!VERSION 3


//!PARAMETER
//!LABEL Sharpness Horizontal
//!DEFAULT 0.5
//!MIN 0
//!MAX 1
//!STEP 0.01
float sharpnessH;

//!PARAMETER
//!LABEL Sharpness Vertical
//!DEFAULT 1
//!MIN 0
//!MAX 1
//!STEP 0.01
float sharpnessV;

//!PARAMETER
//!LABEL Mask Strength
//!DEFAULT 0.3
//!MIN 0
//!MAX 1
//!STEP 0.01
float maskStrength;

//!PARAMETER
//!LABEL Mask Dot Width
//!DEFAULT 1
//!MIN 1
//!MAX 100
//!STEP 1
int maskDotWidth;

//!PARAMETER
//!LABEL Mask Dot Height
//!DEFAULT 1
//!MIN 1
//!MAX 100
//!STEP 1
int maskDotHeight;

//!PARAMETER
//!LABEL Mask Stagger
//!DEFAULT 0
//!MIN 0
//!MAX 100
//!STEP 1
int maskStagger;

//!PARAMETER
//!LABEL Mask Size
//!DEFAULT 1
//!MIN 1
//!MAX 100
//!STEP 1
int maskSize;

//!PARAMETER
//!LABEL Scanline Strength
//!DEFAULT 1
//!MIN 0
//!MAX 1
//!STEP 1
float scanlineStrength;

//!PARAMETER
//!LABEL Scanline Beam Width Min
//!DEFAULT 1.5
//!MIN 0.5
//!MAX 5
//!STEP 0.1
float scanlineBeamWidthMin;

//!PARAMETER
//!LABEL Scanline Beam Width Max
//!DEFAULT 1.5
//!MIN 0.5
//!MAX 5
//!STEP 0.1
float scanlineBeamWidthMax;

//!PARAMETER
//!LABEL Scanline Brightness Min
//!DEFAULT 0.35
//!MIN 0
//!MAX 1
//!STEP 0.01
float scanlineBrightMin;

//!PARAMETER
//!LABEL Scanline Brightness Max
//!DEFAULT 0.65
//!MIN 0
//!MAX 1
//!STEP 0.01
float scanlineBrightMax;

//!PARAMETER
//!LABEL Scanline Cutoff
//!DEFAULT 400
//!MIN 1
//!MAX 1000
//!STEP 1
int scanlineCutoff;

//!PARAMETER
//!LABEL Gamma Input
//!DEFAULT 2
//!MIN 0.1
//!MAX 5
//!STEP 0.01
float gammaInput;

//!PARAMETER
//!LABEL Gamma Output
//!DEFAULT 1.8
//!MIN 0.1
//!MAX 5
//!STEP 0.01
float gammaOutput;

//!PARAMETER
//!LABEL Brightness Boost
//!DEFAULT 1.2
//!MIN 1
//!MAX 2
//!STEP 0.01
float brightBoost;

//!PARAMETER
//!LABEL Dilation
//!DEFAULT 1
//!MIN 0
//!MAX 1
//!STEP 1
int dilation;

//!TEXTURE
Texture2D INPUT;

//!SAMPLER
//!FILTER POINT
SamplerState sam;


//!PASS 1
//!STYLE PS
//!IN INPUT

#pragma warning(disable: 3571) // X3571: pow(f, e) will not work for negative f, use abs(f) or conditionally handle negative values if you expect them

#define FIX(c) max(abs(c), 1e-5)
#define PI 3.141592653589
#define TEX2D(c) dilate(INPUT.SampleLevel(sam, c, 0))
#define mod(x,y) (x - y * trunc(x/y))

// Set to 0 to use linear filter and gain speed
#define ENABLE_LANCZOS 1

float4 dilate(float4 col) {
	float4 x = lerp(float4(1, 1, 1, 1), col, dilation);

	return col * x;
}

float curve_distance(float x, float sharp) {
	/*
		apply half-circle s-curve to distance for sharper (more pixelated) interpolation
		single line formula for Graph Toy:
		0.5 - sqrt(0.25 - (x - step(0.5, x)) * (x - step(0.5, x))) * sign(0.5 - x)
	*/

	float x_step = step(0.5, x);
	float curve = 0.5 - sqrt(0.25 - (x - x_step) * (x - x_step)) * sign(0.5 - x);

	return lerp(x, curve, sharp);
}

float4x4 get_color_matrix(float2 co) {
	float2 inputPt = GetInputPt();
	return float4x4(TEX2D(co - float2(inputPt.x, 0)), TEX2D(co), TEX2D(co + float2(inputPt.x, 0)), TEX2D(co + float2(2.0 * inputPt.x, 0)));
}

float3 filter_lanczos(float4 coeffs, float4x4 color_matrix) {
	float4 col = mul(coeffs, color_matrix);
	float4 sample_min = min(color_matrix[1], color_matrix[2]);
	float4 sample_max = max(color_matrix[1], color_matrix[2]);

	col = clamp(col, sample_min, sample_max);

	return col.rgb;
}

float4 Pass1(float2 pos) {
	float2 inputPt = GetInputPt();
	int2 inputSize = GetInputSize();
	int2 outputSize = GetOutputSize();
	float2 outputPt = GetOutputPt();

	float2 pix_co = pos * inputSize - 0.5f;
	
	float2 tex_co = (floor(pix_co) + 0.5) * inputPt;
	float2 dist = frac(pix_co);
	float curve_x;
	float3 col, col2;

#if ENABLE_LANCZOS
	curve_x = curve_distance(dist.x, sharpnessH * sharpnessH);

	float4 coeffs = PI * float4(1.0 + curve_x, curve_x, 1.0 - curve_x, 2.0 - curve_x);

	coeffs = FIX(coeffs);
	coeffs = 2.0 * sin(coeffs) * sin(coeffs / 2.0) / (coeffs * coeffs);
	coeffs /= dot(coeffs, 1.0);

	col = filter_lanczos(coeffs, get_color_matrix(tex_co));
	col2 = filter_lanczos(coeffs, get_color_matrix(tex_co + float2(0, inputPt.y)));
#else
	curve_x = curve_distance(dist.x, sharpnessH);

	col = lerp(TEX2D(tex_co).rgb, TEX2D(tex_co + float2(inputPt.x, 0)).rgb, curve_x);
	col2 = lerp(TEX2D(tex_co + float2(0, inputPt.y)).rgb, TEX2D(tex_co + float2(inputPt.x, inputPt.y)).rgb, curve_x);
#endif

	col = lerp(col, col2, curve_distance(dist.y, sharpnessV));
	col = pow(col, gammaInput / (dilation + 1.0));

	float luma = dot(float3(0.2126, 0.7152, 0.0722), col);
	float bright = (max(col.r, max(col.g, col.b)) + luma) / 2.0;
	float scan_bright = clamp(bright, scanlineBrightMin, scanlineBrightMax);
	float scan_beam = clamp(bright * scanlineBeamWidthMax, scanlineBeamWidthMin, scanlineBeamWidthMax);
	float scan_weight = 1.0 - pow(cos(pos.y * 2.0 * PI * inputSize.y) * 0.5 + 0.5, scan_beam) * scanlineStrength;

	float mask = 1.0 - maskStrength;
	float2 mod_fac = floor(pos * outputSize / float2(maskSize, maskDotHeight * maskSize));
	int dot_no = int(mod((mod_fac.x + mod(mod_fac.y, 2.0) * maskStagger) / maskDotWidth, 3.0));
	float3 mask_weight;

	if (dot_no == 0) mask_weight = float3(1.0, mask, mask);
	else if (dot_no == 1) mask_weight = float3(mask, 1.0, mask);
	else mask_weight = float3(mask, mask, 1.0);

	if (inputSize.y >= scanlineCutoff) scan_weight = 1.0;

	col2 = col.rgb;
	col *= scan_weight;
	col = lerp(col, col2, scan_bright);
	col *= mask_weight;
	col = pow(col, 1.0 / gammaOutput);

	return float4(col * brightBoost, 1);
}
