From 1475c1b1c8bb1a2a2812d485d3590e1f817f7c7b Mon Sep 17 00:00:00 2001
From: Thomas--S <Thomas--S@users.noreply.github.com>
Date: Fri, 12 Aug 2016 17:56:31 +0200
Subject: [PATCH] Add an [invert:<mode> texture modifier

Inverts the given channels of the base image.
Mode may contain the characters "r", "g", "b", "a".
Only the channels that are mentioned in the mode string will be inverted.
---
 doc/lua_api.txt     |  9 +++++++++
 src/client/tile.cpp | 43 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index aa4f129f0..41e7c00eb 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -318,6 +318,15 @@ Example:
 
     default_sandstone.png^[opacity:127
 
+#### `[invert:<mode>`
+Inverts the given channels of the base image.
+Mode may contain the characters "r", "g", "b", "a".
+Only the channels that are mentioned in the mode string will be inverted.
+
+Example:
+
+	default_apple.png^[invert:rgb
+
 #### `[brighten`
 Brightens the texture.
 
diff --git a/src/client/tile.cpp b/src/client/tile.cpp
index 67d5d8d1a..8f0c39465 100644
--- a/src/client/tile.cpp
+++ b/src/client/tile.cpp
@@ -1783,9 +1783,48 @@ bool TextureSource::generateImagePart(std::string part_of_name,
 			for (u32 y = 0; y < dim.Height; y++)
 			for (u32 x = 0; x < dim.Width; x++)
 			{
-				video::SColor c = baseimg->getPixel(x,y);
+				video::SColor c = baseimg->getPixel(x, y);
 				c.setAlpha(floor((c.getAlpha() * ratio) / 255 + 0.5));
-				baseimg->setPixel(x,y,c);
+				baseimg->setPixel(x, y, c);
+			}
+		}
+		/*
+			[invert:mode
+			Inverts the given channels of the base image.
+			Mode may contain the characters "r", "g", "b", "a".
+			Only the channels that are mentioned in the mode string
+			will be inverted.
+		*/
+		else if (str_starts_with(part_of_name, "[invert:")) {
+			if (baseimg == NULL) {
+				errorstream << "generateImagePart(): baseimg == NULL "
+						<< "for part_of_name=\"" << part_of_name
+						<< "\", cancelling." << std::endl;
+				return false;
+			}
+
+			Strfnd sf(part_of_name);
+			sf.next(":");
+
+			std::string mode = sf.next("");
+			u32 mask = 0;
+			if (mode.find("a") != std::string::npos)
+				mask |= 0xff000000UL;
+			if (mode.find("r") != std::string::npos)
+				mask |= 0x00ff0000UL;
+			if (mode.find("g") != std::string::npos)
+				mask |= 0x0000ff00UL;
+			if (mode.find("b") != std::string::npos)
+				mask |= 0x000000ffUL;
+
+			core::dimension2d<u32> dim = baseimg->getDimension();
+
+			for (u32 y = 0; y < dim.Height; y++)
+			for (u32 x = 0; x < dim.Width; x++)
+			{
+				video::SColor c = baseimg->getPixel(x, y);
+				c.color ^= mask;	
+				baseimg->setPixel(x, y, c);
 			}
 		}
 		else