From 3ad07543beadb4fa292422bcace54918b00adf7b Mon Sep 17 00:00:00 2001
From: cutealien <cutealien@dfc29bdd-3216-0410-991c-e03cc46cb475>
Date: Tue, 8 Mar 2022 18:44:23 +0000
Subject: [PATCH] Add IGUIImage::flip to allow flipping/mirroring images.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6301 dfc29bdd-3216-0410-991c-e03cc46cb475
---
 changes.txt                |  1 +
 include/IImage.h           |  6 ++++-
 source/Irrlicht/CImage.cpp | 54 ++++++++++++++++++++++++++++++++++++++
 source/Irrlicht/CImage.h   |  3 +++
 4 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/changes.txt b/changes.txt
index b9b3b27f..91007b75 100644
--- a/changes.txt
+++ b/changes.txt
@@ -1,5 +1,6 @@
 --------------------------
 Changes in 1.9 (not yet released)
+- Add IGUIImage::flip to flip/mirror images
 - IBillboardSceneNode got functions to access meshbuffers. So uv-coordinates can now be modified directly (previously only possible via texture matrix).
 - vector3d scalar operator/ and operator/= no longer multiply by the inverse but use the expected division. 
   Costs some speed, but fixes floating point troubles caused by this optimization (like x/x no longer being 1.0).
diff --git a/include/IImage.h b/include/IImage.h
index 92029b2f..b09d3c26 100644
--- a/include/IImage.h
+++ b/include/IImage.h
@@ -74,7 +74,6 @@ public:
 	//! Returns bits per pixel.
 	u32 getBitsPerPixel() const
 	{
-
 		return getBitsPerPixelFromFormat(Format);
 	}
 
@@ -359,6 +358,11 @@ public:
 	/**	NOTE: mipmaps are ignored */
 	virtual void copyToScalingBoxFilter(IImage* target, s32 bias = 0, bool blend = false) = 0;
 
+	//! Flips (mirrors) the image in one or two directions
+	/** \param topBottom Flip around central x-axis (vertical flipping)
+	\param leftRight Flip around central y-axis (typical mirror, horizontal flipping) */
+	virtual void flip(bool topBottom, bool leftRight) = 0;
+
 	//! fills the surface with given color
 	virtual void fill(const SColor &color) =0;
 
diff --git a/source/Irrlicht/CImage.cpp b/source/Irrlicht/CImage.cpp
index 753262b7..182623d0 100644
--- a/source/Irrlicht/CImage.cpp
+++ b/source/Irrlicht/CImage.cpp
@@ -347,6 +347,60 @@ void CImage::fill(const SColor &color)
 	memset32( Data, c, getImageDataSizeInBytes() );
 }
 
+void CImage::flip(bool topBottom, bool leftRight)
+{
+	if ( !topBottom && !leftRight)
+		return;
+
+	const core::dimension2du dim(getDimension());
+	if ( dim.Width == 0 || dim.Height == 0 )
+		return;
+
+	u8* data = (u8*)getData();
+	if (!data) 
+		return;
+
+	const u32 bpp = getBytesPerPixel();
+	const u32 pitch = getPitch();
+
+	if ( topBottom )
+	{
+		for ( u32 i=0; i<dim.Height/2; ++i)
+		{
+			// Reverse bottom/top lines
+			u8* l1 = data+i*pitch;
+			u8* l2 = data+(dim.Height-1-i)*pitch;
+			for ( u32 b=0; b<pitch; ++b)
+			{
+				irr::u8 dummy = *l1;
+				*l1 = *l2;
+				*l2 = dummy;
+				++l1;
+				++l2;
+			}
+		}
+	}
+	if ( leftRight )
+	{
+		for ( u32 i=0; i<dim.Height; ++i)
+		{
+			// Reverse left/right for each line
+			u8* l1 = data+i*pitch;
+			u8* l2 = l1+(dim.Width-1)*bpp;
+			for ( u32 p=0; p<dim.Width/2; ++p)
+			{
+				for ( u32 b=0; b<bpp; ++b)
+				{
+					irr::u8 dummy = l1[b];
+					l1[b] = l2[b];
+					l2[b] = dummy;
+				}
+				l1 += bpp;
+				l2 -= bpp;
+			}
+		}
+	}
+}
 
 //! get a filtered pixel
 inline SColor CImage::getPixelBox( s32 x, s32 y, s32 fx, s32 fy, s32 bias ) const
diff --git a/source/Irrlicht/CImage.h b/source/Irrlicht/CImage.h
index 523935bb..1f0ae700 100644
--- a/source/Irrlicht/CImage.h
+++ b/source/Irrlicht/CImage.h
@@ -55,6 +55,9 @@ public:
 	//! copies this surface into another, scaling it to fit, applying a box filter
 	virtual void copyToScalingBoxFilter(IImage* target, s32 bias = 0, bool blend = false) IRR_OVERRIDE;
 
+	//! Flips (mirrors) the image in one or two directions
+	virtual void flip(bool topBottom, bool leftRight) IRR_OVERRIDE;
+
 	//! fills the surface with given color
 	virtual void fill(const SColor &color) IRR_OVERRIDE;