/*
MMJ's Cel Shader - v1.03
----------------------------------------------------------------
-- 180403 --
This is a port of my old shader from around 2006 for Pete's OGL2
plugin for ePSXe. It started out as a shader based on the
"CComic" shader by Maruke. I liked his concept, but I was
looking for something a little different in the output.

Since the last release, I've seen some test screenshots from MAME
using a port of my original shader and have also seen another
port to get it working with the PCSX2 emulator. Having recently
seen some Kingdom Hearts II and Soul Calibur 3 YouTube videos with
my ported shader inspired me to revisit it and get it working in
RetroArch.

As for this version (1.03), I've made a few small modifications
(such as to remove the OGL2Param references, which were specific
to Pete's plugin) and I added some RetroArch Parameter support,
so some values can now be changed in real time.

Keep in mind, that this was originally developed for PS1, using
various 3D games as a test. In general, it will look better in
games with less detailed textures, as "busy" textures will lead
to more outlining / messy appearance. Increasing "Outline
Brightness" can help mitigate this some by lessening the
"strength" of the outlines.

Also (in regards to PS1 - I haven't really tested other systems
too much yet), 1x internal resolution will look terrible. 2x
will also probably be fairly blurry/messy-looking. For best
results, you should probably stick to 4x or higher internal
resolution with this shader.

Parameters:
-----------
White Level Cutoff = Anything above this luminance value will be
    forced to pure white.

Black Level Cutoff = Anything below this luminance value will be
    forced to pure black.

Shading Levels = Determines how many color "slices" there should
    be (not counting black/white cutoffs, which are always
    applied).

Saturation Modifier = Increase or decrease color saturation.
    Default value boosts saturation a little for a more
    cartoonish look. Set to 0.00 for grayscale.

Outline Brightness = Adjusts darkness of the outlines. At a
    setting of 1, outlines should be disabled.

Shader Strength = Adjusts the weight of the color banding
    portion of the shader from 0% (0.00) to 100% (1.00). At a
    setting of 0.00, you can turn off the color banding effect
    altogether, but still keep outlines enabled.
-----------
MMJuno
*/

#include "ReShade.fxh"

uniform float WhtCutoff <
    ui_type = "drag";
    ui_min = 0.50;
    ui_max = 1.0;
    ui_step = 0.01;
    ui_label = "White Level Cutoff [MMJCelShader]";
> = 0.97;

uniform float BlkCutoff <
    ui_type = "drag";
    ui_min = 0.0;
    ui_max = 0.5;
    ui_step = 0.01;
    ui_label = "Black Level Cutoff [MMJCelShader]";
> = 0.03;

uniform float ShdLevels <
    ui_type = "drag";
    ui_min = 1.0;
    ui_max = 16.0;
    ui_step = 1.0;
    ui_label = "Shading Levels [MMJCelShader]";
> = 9.0;

uniform float SatModify <
    ui_type = "drag";
    ui_min = 0.0;
    ui_max = 2.0;
    ui_step = 0.01;
    ui_label = "Saturation Modifier [MMJCelShader]";
> = 1.15;

uniform float OtlModify <
    ui_type = "drag";
    ui_min = 0.0;
    ui_max = 1.0;
    ui_step = 0.01;
    ui_label = "Outline Brightness [MMJCelShader]";
> = 0.20;

uniform float ShdWeight <
    ui_type = "drag";
    ui_min = 0.0;
    ui_max = 1.0;
    ui_step = 0.01;
    ui_label = "Shader Strength [MMJCelShader]";
> = 0.50;

sampler RetroArchSRGB { Texture = ReShade::BackBufferTex; MinFilter = LINEAR; MagFilter = LINEAR; MipFilter = LINEAR; SRGBTexture = true;};

#define mod(x,y) (x-y*floor(x/y))

float3 RGB2HCV(in float3 RGB)
{
    RGB = saturate(RGB);
    float Epsilon = 1e-10;
        // Based on work by Sam Hocevar and Emil Persson
        float4 P = (RGB.g < RGB.b) ? float4(RGB.bg, -1.0, 2.0/3.0) : float4(RGB.gb, 0.0, -1.0/3.0);
        float4 Q = (RGB.r < P.x) ? float4(P.xyw, RGB.r) : float4(RGB.r, P.yzx);
        float C = Q.x - min(Q.w, Q.y);
        float H = abs((Q.w - Q.y) / (6 * C + Epsilon) + Q.z);
        return float3(H, C, Q.x);
}

float3 RGB2HSL(in float3 RGB)
{
        float3 HCV = RGB2HCV(RGB);
        float L = HCV.z - HCV.y * 0.5;
        float S = HCV.y / (1.0000001 - abs(L * 2 - 1));
        return float3(HCV.x, S, L);
}

float3 HSL2RGB(in float3 HSL)
{
    HSL = saturate(HSL);
    //HSL.z *= 0.99;
        float3 RGB = saturate(float3(abs(HSL.x * 6.0 - 3.0) - 1.0,2.0 - abs(HSL.x * 6.0 - 2.0),2.0 - abs(HSL.x * 6.0 - 4.0)));
        float C = (1 - abs(2 * HSL.z - 1)) * HSL.y;
        return (RGB - 0.5) * C + HSL.z;
}

float3 colorAdjust(float3 cRGB)
{
    float3 cHSL = RGB2HSL(cRGB);

    float cr = 1.0 / ShdLevels;

    // brightness modifier
    float BrtModify = mod(cHSL.z, cr);

    if     (cHSL.z > WhtCutoff) { cHSL.y  = 1.0; cHSL.z = 1.0; }
    else if(cHSL.z > BlkCutoff) { cHSL.y *= SatModify; cHSL.z += (cHSL.z * cr - BrtModify); }
    else                         { cHSL.y  = 0.0; cHSL.z = 0.0; }
    cRGB = 1.2 * HSL2RGB(cHSL);

    return cRGB;
}

void PS_MMJCel(in float4 pos : SV_POSITION, in float2 texcoord : TEXCOORD0, out float4 fragColor : COLOR0)
{

    float2 offset = float2(0.0,0.0);
    float2 offset_inv = float2(0.0,0.0);
    float2 TEX0 = texcoord.xy;
    float2 TEX1 = float2(0.0,0.0);
    float2 TEX1_INV = float2(0.0,0.0);
    float2 TEX2 = float2(0.0,0.0);
    float2 TEX2_INV = float2(0.0,0.0);
    float2 TEX3 = float2(0.0,0.0);
    float2 TEX3_INV = float2(0.0,0.0);

    offset = -(float2(1.0 / ReShade::ScreenSize.x, 0.0)); //XY
    offset_inv = float2(1.0 / ReShade::ScreenSize.x,0.0); //ZW
    TEX1 = TEX0 + offset;
    TEX1_INV = TEX0 + offset_inv;

    offset = -(float2(0.0,(1.0 / ReShade::ScreenSize.y))); //XY
    offset_inv = float2(0.0, (1.0 / ReShade::ScreenSize.y)); //ZW

    TEX2 = TEX0.xy + offset;
    TEX2_INV = TEX0.xy + offset_inv;
    TEX3 = TEX1.xy + offset;
    TEX3_INV = TEX1.xy + offset_inv;

    float3 c0 = tex2D(RetroArchSRGB, TEX3.xy).rgb;
    float3 c1 = tex2D(RetroArchSRGB, TEX2.xy).rgb;
    float3 c2 = tex2D(RetroArchSRGB, float2(TEX3_INV.x,TEX3.y)).rgb;
    float3 c3 = tex2D(RetroArchSRGB, TEX1.xy).rgb;
    float3 c4 = tex2D(RetroArchSRGB, TEX0.xy).rgb;
    float3 c5 = tex2D(RetroArchSRGB, TEX1_INV.xy).rgb;
    float3 c6 = tex2D(RetroArchSRGB, float2(TEX3.x,TEX3_INV.y)).rgb;
    float3 c7 = tex2D(RetroArchSRGB, TEX2_INV).rgb;
    float3 c8 = tex2D(RetroArchSRGB, TEX3_INV).rgb;
    float3 c9 = ((c0 + c2 + c6 + c8) * 0.15 + (c1 + c3 + c5 + c7) * 0.25 + c4) / 2.6;

    float3 o = float3(1.0,1.0,1.0);
    float3 h = float3(0.05,0.05,0.05);
    float3 hz = h;
    float k = 0.005;
    float kz = 0.007;
    float i = 0.0;

    float3 cz = (c9 + h) / (dot(o, c9) + k);
    float3 col = float3(0.0,0.0,0.0);

    hz = (cz - ((c0 + h) / (dot(o, c0) + k))); i  = kz / (dot(hz, hz) + kz);
    hz = (cz - ((c1 + h) / (dot(o, c1) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c2 + h) / (dot(o, c2) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c3 + h) / (dot(o, c3) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c5 + h) / (dot(o, c5) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c6 + h) / (dot(o, c6) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c7 + h) / (dot(o, c7) + k))); i += kz / (dot(hz, hz) + kz);
    hz = (cz - ((c8 + h) / (dot(o, c8) + k))); i += kz / (dot(hz, hz) + kz);

    i /= 8.0;
    i = pow(i, 0.75);

    if(i < OtlModify) { i = OtlModify; }
    c9 = min(o, min(c9, c9 + dot(o, c9)));
    col = lerp(c4 * i, colorAdjust(c9 * i), ShdWeight);
    fragColor = float4(col,1.0);
}

technique MMJCelShader {
    pass MMJCelShader {
        VertexShader=PostProcessVS;
        PixelShader=PS_MMJCel;
        SRGBWriteEnable = true;
    }
}