From 611d26a7c8254d15f8aa9250969e3357feea5e64 Mon Sep 17 00:00:00 2001
From: Mr-Wiseguy <mrwiseguyromhacking@gmail.com>
Date: Wed, 1 May 2024 04:19:46 -0400
Subject: [PATCH] Added missing changes in shader include files for dithering

---
 src/shaders/FbCommon.hlsli |  8 +++---
 src/shaders/Formats.hlsli  | 59 ++++++++++++++++++++++++++++++++++----
 2 files changed, 57 insertions(+), 10 deletions(-)

diff --git a/src/shaders/FbCommon.hlsli b/src/shaders/FbCommon.hlsli
index dc82f08..28303b7 100644
--- a/src/shaders/FbCommon.hlsli
+++ b/src/shaders/FbCommon.hlsli
@@ -103,10 +103,10 @@ uint Float4ToUINT8(float4 i, uint fmt, bool oddColumn) {
     }
 }
 
-uint Float4ToUINT16(float4 i, uint fmt) {
+uint Float4ToUINT16(float4 i, uint fmt, uint dither) {
     switch (fmt) {
     case G_IM_FMT_RGBA:
-        return Float4ToRGBA16(i);
+        return Float4ToRGBA16(i, dither);
     // TODO
     case G_IM_FMT_CI:
         return 0;
@@ -141,7 +141,7 @@ uint Float4ToUINT32(float4 i, uint fmt) {
     }
 }
 
-uint Float4ToUINT(float4 i, uint siz, uint fmt, bool oddColumn) {
+uint Float4ToUINT(float4 i, uint siz, uint fmt, bool oddColumn, uint dither) {
     switch (siz) {
     // TODO
     case G_IM_SIZ_4b:
@@ -149,7 +149,7 @@ uint Float4ToUINT(float4 i, uint siz, uint fmt, bool oddColumn) {
     case G_IM_SIZ_8b:
         return Float4ToUINT8(i, fmt, oddColumn);
     case G_IM_SIZ_16b:
-        return Float4ToUINT16(i, fmt);
+        return Float4ToUINT16(i, fmt, dither);
     case G_IM_SIZ_32b:
         return Float4ToUINT32(i, fmt);
     // Invalid pixel size.
diff --git a/src/shaders/Formats.hlsli b/src/shaders/Formats.hlsli
index 9854a0b..ab3dd16 100644
--- a/src/shaders/Formats.hlsli
+++ b/src/shaders/Formats.hlsli
@@ -6,6 +6,53 @@
 
 // Color conversion formulas sourced from Tharo.
 
+static const uint DitherPatternBayer[16] = {
+    0, 4, 1, 5,
+    4, 0, 5, 1,
+    3, 7, 2, 6,
+    7, 3, 6, 2
+};
+
+static const uint DitherPatternMagicSquare[16] = {
+    0, 6, 1, 7,
+    4, 2, 5, 3,
+    3, 5, 2, 4,
+    7, 1, 6, 0
+};
+
+uint DitherPatternIndex(uint2 coord) {
+    return ((coord.y & 3) << 2) + (coord.x & 3);
+}
+
+uint DitherPatternValue(uint pattern, uint2 coord, uint randomSeed) {
+    switch (pattern) {
+    case 0: // MAGICSQ
+        return DitherPatternMagicSquare[DitherPatternIndex(coord)];
+    case 1: // BAYER
+        return DitherPatternBayer[DitherPatternIndex(coord)];
+    case 2: // NOISE
+        return randomSeed & 7;
+    case 3: // DISABLE
+    default:
+        return 0;
+    }
+}
+
+uint AlphaDitherValue(uint colorDither, uint alphaDither, uint2 coord, uint randomSeed) {
+    // Only the first bit of color dither is used here for pattern selection.
+    switch (alphaDither) {
+    case 0: // PATTERN
+        return DitherPatternValue(colorDither & 1, coord, randomSeed);
+    case 1: // NOTPATTERN
+        return (~DitherPatternValue(colorDither & 1, coord, randomSeed)) & 7;
+    case 2: // NOISE
+        return randomSeed & 7;
+    case 3: // DISABLE
+    default:
+        return 0;
+    }
+}
+
 float4 I4ToFloat4(uint i4) {
     uint i = (i4 << 4) | i4;
     return i / 255.0f;
@@ -45,15 +92,15 @@ float4 RGBA16ToFloat4(uint rgba16) {
     );
 }
 
-uint Float4ToRGBA16(float4 i) {
+uint Float4ToRGBA16(float4 i, uint dither) {
     uint r = round(clamp(i.r * 255.0f, 0.0f, 255.0f));
     uint g = round(clamp(i.g * 255.0f, 0.0f, 255.0f));
     uint b = round(clamp(i.b * 255.0f, 0.0f, 255.0f));
-	int cvgModulo = round(i.a * 255.0f) % 8;
-	uint a = (cvgModulo & 0x4) ? 1 : 0;
-    r = r >> 3;
-    g = g >> 3;
-    b = b >> 3;
+    int cvgModulo = round(i.a * 255.0f) % 8;
+    uint a = (cvgModulo & 0x4) ? 1 : 0;
+    r = min(r + dither, 255) >> 3;
+    g = min(g + dither, 255) >> 3;
+    b = min(b + dither, 255) >> 3;
     return (r << 11) | (g << 6) | (b << 1) | a;
 }