From cea7f095bb921ac963e5a01a9c20bece84468ace Mon Sep 17 00:00:00 2001
From: UnknownShadow200 <unknownshadow200@gmail.com>
Date: Fri, 10 May 2019 22:42:50 +1000
Subject: [PATCH] If non-alex area of skin arms are completely black, treat as
 alex skin

This fixes skins saved by services that lose transparency
---
 src/Entity.c |  8 ++++----
 src/Game.c   |  2 +-
 src/Utils.c  | 23 ++++++++++++++++++++---
 src/Utils.h  |  2 +-
 4 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/Entity.c b/src/Entity.c
index b1ddd90ff..d1088eb3d 100644
--- a/src/Entity.c
+++ b/src/Entity.c
@@ -660,13 +660,13 @@ static void Player_ClearHat(Bitmap* bmp, uint8_t skinType) {
 	}
 
 	/* only perform filtering when the entire hat is opaque */
-	uint32_t fullWhite = PackedCol_ARGB(255, 255, 255, 255);
-	uint32_t fullBlack = PackedCol_ARGB(0,   0,   0,   255);
+	uint32_t white = PackedCol_ARGB(255, 255, 255, 255);
+	uint32_t black = PackedCol_ARGB(0,   0,   0,   255);
 	for (y = 0; y < sizeY; y++) {
 		uint32_t* row = Bitmap_RawRow(bmp, y) + sizeX;
 		for (x = 0; x < sizeX; x++) {
 			uint32_t pixel = row[x];
-			if (pixel == fullWhite || pixel == fullBlack) row[x] = 0;
+			if (pixel == white || pixel == black) row[x] = 0;
 		}
 	}
 }
@@ -730,7 +730,7 @@ static void Player_CheckSkin(struct Player* p) {
 	Gfx_DeleteTexture(&e->TextureId);
 	Player_SetSkinAll(p, true);
 	Player_EnsurePow2(p, &bmp);
-	e->SkinType = Utils_GetSkinType(&bmp);
+	e->SkinType = Utils_CalcSkinType(&bmp);
 
 	if (bmp.Width > Gfx.MaxTexWidth || bmp.Height > Gfx.MaxTexHeight) {
 		Chat_Add1("&cSkin %s is too large", &skin);
diff --git a/src/Game.c b/src/Game.c
index 5c986f32b..c9d4c39da 100644
--- a/src/Game.c
+++ b/src/Game.c
@@ -237,7 +237,7 @@ bool Game_UpdateTexture(GfxResourceID* texId, struct Stream* src, const String*
 	success = !res && Game_ValidateBitmap(file, &bmp);
 	if (success) {
 		Gfx_DeleteTexture(texId);
-		if (skinType) { *skinType = Utils_GetSkinType(&bmp); }
+		if (skinType) { *skinType = Utils_CalcSkinType(&bmp); }
 		*texId = Gfx_CreateTexture(&bmp, true, false);
 	}
 
diff --git a/src/Utils.c b/src/Utils.c
index c6701d044..d7f8dc2f9 100644
--- a/src/Utils.c
+++ b/src/Utils.c
@@ -140,14 +140,31 @@ int Utils_AccumulateWheelDelta(float* accumulator, float delta) {
 	return steps;
 }
 
-uint8_t Utils_GetSkinType(const Bitmap* bmp) {
+/* Checks if an area is completely black, so Alex skins edited with Microsoft Paint are still treated as Alex */
+static bool Utils_IsAllBlack(const Bitmap* bmp, int x1, int y1, int width, int height) {
+	uint32_t black = PackedCol_ARGB(0, 0, 0, 255);
+	int x, y;
+	for (y = y1; y < y1 + height; y++) {
+		uint32_t* row = Bitmap_RawRow(bmp, y);
+
+		for (x = x1; x < x1 + width; x++) {
+			if (row[x] != black) return false;
+		}
+	}
+	return true;
+}
+
+uint8_t Utils_CalcSkinType(const Bitmap* bmp) {
 	int scale;
 	if (bmp->Width == bmp->Height * 2) return SKIN_64x32;
 	if (bmp->Width != bmp->Height)     return SKIN_INVALID;
 
-	/* Minecraft alex skins have this particular pixel with alpha of 0 */
 	scale = bmp->Width / 64;
-	return Bitmap_GetPixel(bmp, 54 * scale, 20 * scale).A >= 127 ? SKIN_64x64 : SKIN_64x64_SLIM;
+	/* Minecraft alex skins have this particular pixel with alpha of 0 */	
+	if (Bitmap_GetPixel(bmp, 54 * scale, 20 * scale).A < 128) return SKIN_64x64_SLIM;
+
+	return Utils_IsAllBlack(bmp, 54 * scale, 20 * scale, 2 * scale, 12 * scale)
+		&& Utils_IsAllBlack(bmp, 50 * scale, 16 * scale, 2 * scale,  4 * scale) ? SKIN_64x64_SLIM : SKIN_64x64;
 }
 
 uint32_t Utils_CRC32(const uint8_t* data, uint32_t length) {
diff --git a/src/Utils.h b/src/Utils.h
index dfcb774ff..7564e127a 100644
--- a/src/Utils.h
+++ b/src/Utils.h
@@ -40,7 +40,7 @@ void Utils_UNSAFE_GetFilename(STRING_REF String* path);
 int Utils_AccumulateWheelDelta(float* accumulator, float delta);
 #define Utils_AdjViewDist(value) ((int)(1.4142135f * (value)))
 
-uint8_t Utils_GetSkinType(const Bitmap* bmp);
+uint8_t Utils_CalcSkinType(const Bitmap* bmp);
 uint32_t Utils_CRC32(const uint8_t* data, uint32_t length);
 /* CRC32 lookup table, for faster CRC32 calculations. */
 /* NOTE: This cannot be just indexed by byte value - see Utils_CRC32 implementation. */