Clean scaling pre-filter for formspec/HUD.

18 files changed, 509 insertions, 102 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b33bea87b..a1c2d013c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -405,9 +405,11 @@ set(client_SRCS
 	guiFormSpecMenu.cpp
 	guiKeyChangeMenu.cpp
 	guiPasswordChange.cpp
+	guiscalingfilter.cpp
 	guiTable.cpp
 	guiVolumeChange.cpp
 	hud.cpp
+	imagefilters.cpp
 	keycode.cpp
 	localplayer.cpp
 	main.cpp
diff --git a/src/client.cpp b/src/client.cpp
index dc2b54e9b..ba78cb51e 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -49,6 +49,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "drawscene.h"
 #include "database-sqlite3.h"
 #include "serialization.h"
+#include "guiscalingfilter.h"
 
 extern gui::IGUIEnvironment* guienv;
 
@@ -1607,6 +1608,11 @@ void Client::afterContentReceived(IrrlichtDevice *device)
 
 	const wchar_t* text = wgettext("Loading textures...");
 
+	// Clear cached pre-scaled 2D GUI images, as this cache
+	// might have images with the same name but different
+	// content from previous sessions.
+	guiScalingCacheClear(device->getVideoDriver());
+
 	// Rebuild inherited images and recreate textures
 	infostream<<"- Rebuilding images and textures"<<std::endl;
 	draw_load_screen(text,device, guienv, 0, 70);
diff --git a/src/client/tile.cpp b/src/client/tile.cpp
index b7f63502d..283b262a6 100644
--- a/src/client/tile.cpp
+++ b/src/client/tile.cpp
@@ -34,6 +34,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "gamedef.h"
 #include "strfnd.h"
 #include "util/string.h" // for parseColorString()
+#include "imagefilters.h"
+#include "guiscalingfilter.h"
 
 #ifdef __ANDROID__
 #include <GLES/gl.h>
@@ -223,58 +225,9 @@ public:
 			}
 		}
 
-		/* Apply the "clean transparent" filter to textures, removing borders on transparent textures.
-		 * PNG optimizers discard RGB values of fully-transparent pixels, but filters may expose the
-		 * replacement colors at borders by blending to them; this filter compensates for that by
-		 * filling in those RGB values from nearby pixels.
-		 */
-		if (g_settings->getBool("texture_clean_transparent")) {
-			const core::dimension2d<u32> dim = toadd->getDimension();
-
-			// Walk each pixel looking for ones that will show as transparent.
-			for (u32 ctrx = 0; ctrx < dim.Width; ctrx++)
-			for (u32 ctry = 0; ctry < dim.Height; ctry++) {
-				irr::video::SColor c = toadd->getPixel(ctrx, ctry);
-				if (c.getAlpha() > 127)
-					continue;
-
-				// Sample size and total weighted r, g, b values.
-				u32 ss = 0, sr = 0, sg = 0, sb = 0;
-
-				// Walk each neighbor pixel (clipped to image bounds).
-				for (u32 sx = (ctrx < 1) ? 0 : (ctrx - 1);
-						sx <= (ctrx + 1) && sx < dim.Width; sx++)
-				for (u32 sy = (ctry < 1) ? 0 : (ctry - 1);
-						sy <= (ctry + 1) && sy < dim.Height; sy++) {
-
-					// Ignore the center pixel (its RGB is already
-					// presumed meaningless).
-					if ((sx == ctrx) && (sy == ctry))
-						continue;
-
-					// Ignore other nearby pixels that would be
-					// transparent upon display.
-					irr::video::SColor d = toadd->getPixel(sx, sy);
-					if(d.getAlpha() < 128)
-						continue;
-
-					// Add one weighted sample.
-					ss++;
-					sr += d.getRed();
-					sg += d.getGreen();
-					sb += d.getBlue();
-				}
-
-				// If we found any neighbor RGB data, set pixel to average
-				// weighted by alpha.
-				if (ss > 0) {
-					c.setRed(sr / ss);
-					c.setGreen(sg / ss);
-					c.setBlue(sb / ss);
-					toadd->setPixel(ctrx, ctry, c);
-				}
-			}
-		}
+		// Apply the "clean transparent" filter, if configured.
+		if (g_settings->getBool("texture_clean_transparent"))
+			imageCleanTransparent(toadd, 127);
 
 		if (need_to_grab)
 			toadd->grab();
@@ -670,6 +623,7 @@ u32 TextureSource::generateTexture(const std::string &name)
 #endif
 		// Create texture from resulting image
 		tex = driver->addTexture(name.c_str(), img);
+		guiScalingCache(io::path(name.c_str()), driver, img);
 		img->drop();
 	}
 
@@ -776,6 +730,7 @@ void TextureSource::rebuildImagesAndTextures()
 		video::ITexture *t = NULL;
 		if (img) {
 			t = driver->addTexture(ti->name.c_str(), img);
+			guiScalingCache(io::path(ti->name.c_str()), driver, img);
 			img->drop();
 		}
 		video::ITexture *t_old = ti->texture;
@@ -896,6 +851,8 @@ video::ITexture* TextureSource::generateTextureFromMesh(
 		rawImage->copyToScaling(inventory_image);
 		rawImage->drop();
 
+		guiScalingCache(io::path(params.rtt_texture_name.c_str()), driver, inventory_image);
+
 		video::ITexture *rtt = driver->addTexture(params.rtt_texture_name.c_str(), inventory_image);
 		inventory_image->drop();
 
diff --git a/src/client/tile.h b/src/client/tile.h
index eadfdc2a5..38f8bb623 100644
--- a/src/client/tile.h
+++ b/src/client/tile.h
@@ -28,6 +28,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "threads.h"
 #include <string>
 #include <vector>
+#include "util/numeric.h"
 
 class IGameDef;
 
@@ -135,21 +136,6 @@ public:
 IWritableTextureSource* createTextureSource(IrrlichtDevice *device);
 
 #ifdef __ANDROID__
-/**
- * @param size get next npot2 value
- * @return npot2 value
- */
-inline unsigned int npot2(unsigned int size)
-{
-	if (size == 0) return 0;
-	unsigned int npot = 1;
-
-	while ((size >>= 1) > 0) {
-		npot <<= 1;
-	}
-	return npot;
-}
-
 video::IImage * Align2Npot2(video::IImage * image, video::IVideoDriver* driver);
 #endif
 
diff --git a/src/defaultsettings.cpp b/src/defaultsettings.cpp
index 0acb4a730..6fa420b69 100644
--- a/src/defaultsettings.cpp
+++ b/src/defaultsettings.cpp
@@ -137,6 +137,8 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("crosshair_alpha", "255");
 	settings->setDefault("hud_scaling", "1.0");
 	settings->setDefault("gui_scaling", "1.0");
+	settings->setDefault("gui_scaling_filter", "false");
+	settings->setDefault("gui_scaling_filter_txr2img", "true");
 	settings->setDefault("mouse_sensitivity", "0.2");
 	settings->setDefault("enable_sound", "true");
 	settings->setDefault("sound_volume", "0.8");
diff --git a/src/drawscene.cpp b/src/drawscene.cpp
index b089e71e6..c3c3b2ef2 100644
--- a/src/drawscene.cpp
+++ b/src/drawscene.cpp
@@ -24,6 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "clientmap.h"
 #include "util/timetaker.h"
 #include "fontengine.h"
+#include "guiscalingfilter.h"
 
 typedef enum {
 	LEFT = -1,
@@ -324,19 +325,19 @@ void draw_sidebyside_3d_mode(Camera& camera, bool show_hud,
 	//makeColorKeyTexture mirrors texture so we do it twice to get it right again
 	driver->makeColorKeyTexture(hudtexture, irr::video::SColor(255, 0, 0, 0));
 
-	driver->draw2DImage(left_image,
+	draw2DImageFilterScaled(driver, left_image,
 			irr::core::rect<s32>(0, 0, screensize.X/2, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, false);
 
-	driver->draw2DImage(hudtexture,
+	draw2DImageFilterScaled(driver, hudtexture,
 			irr::core::rect<s32>(0, 0, screensize.X/2, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, true);
 
-	driver->draw2DImage(right_image,
+	draw2DImageFilterScaled(driver, right_image,
 			irr::core::rect<s32>(screensize.X/2, 0, screensize.X, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, false);
 
-	driver->draw2DImage(hudtexture,
+	draw2DImageFilterScaled(driver, hudtexture,
 			irr::core::rect<s32>(screensize.X/2, 0, screensize.X, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, true);
 
@@ -380,19 +381,19 @@ void draw_top_bottom_3d_mode(Camera& camera, bool show_hud,
 	//makeColorKeyTexture mirrors texture so we do it twice to get it right again
 	driver->makeColorKeyTexture(hudtexture, irr::video::SColor(255, 0, 0, 0));
 
-	driver->draw2DImage(left_image,
+	draw2DImageFilterScaled(driver, left_image,
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y/2),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, false);
 
-	driver->draw2DImage(hudtexture,
+	draw2DImageFilterScaled(driver, hudtexture,
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y/2),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, true);
 
-	driver->draw2DImage(right_image,
+	draw2DImageFilterScaled(driver, right_image,
 			irr::core::rect<s32>(0, screensize.Y/2, screensize.X, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, false);
 
-	driver->draw2DImage(hudtexture,
+	draw2DImageFilterScaled(driver, hudtexture,
 			irr::core::rect<s32>(0, screensize.Y/2, screensize.X, screensize.Y),
 			irr::core::rect<s32>(0, 0, screensize.X, screensize.Y), 0, 0, true);
 
diff --git a/src/guiEngine.cpp b/src/guiEngine.cpp
index c143e5110..07fdbb16e 100644
--- a/src/guiEngine.cpp
+++ b/src/guiEngine.cpp
@@ -36,6 +36,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "httpfetch.h"
 #include "log.h"
 #include "fontengine.h"
+#include "guiscalingfilter.h"
 
 #ifdef __ANDROID__
 #include "client/tile.h"
@@ -409,7 +410,7 @@ void GUIEngine::drawBackground(video::IVideoDriver* driver)
 		{
 			for (unsigned int y = 0; y < screensize.Y; y += tilesize.Y )
 			{
-				driver->draw2DImage(texture,
+				draw2DImageFilterScaled(driver, texture,
 					core::rect<s32>(x, y, x+tilesize.X, y+tilesize.Y),
 					core::rect<s32>(0, 0, sourcesize.X, sourcesize.Y),
 					NULL, NULL, true);
@@ -419,7 +420,7 @@ void GUIEngine::drawBackground(video::IVideoDriver* driver)
 	}
 
 	/* Draw background texture */
-	driver->draw2DImage(texture,
+	draw2DImageFilterScaled(driver, texture,
 		core::rect<s32>(0, 0, screensize.X, screensize.Y),
 		core::rect<s32>(0, 0, sourcesize.X, sourcesize.Y),
 		NULL, NULL, true);
@@ -438,7 +439,7 @@ void GUIEngine::drawOverlay(video::IVideoDriver* driver)
 
 	/* Draw background texture */
 	v2u32 sourcesize = texture->getOriginalSize();
-	driver->draw2DImage(texture,
+	draw2DImageFilterScaled(driver, texture,
 		core::rect<s32>(0, 0, screensize.X, screensize.Y),
 		core::rect<s32>(0, 0, sourcesize.X, sourcesize.Y),
 		NULL, NULL, true);
@@ -471,7 +472,7 @@ void GUIEngine::drawHeader(video::IVideoDriver* driver)
 
 	video::SColor bgcolor(255,50,50,50);
 
-	driver->draw2DImage(texture, splashrect,
+	draw2DImageFilterScaled(driver, texture, splashrect,
 		core::rect<s32>(core::position2d<s32>(0,0),
 		core::dimension2di(texture->getOriginalSize())),
 		NULL, NULL, true);
@@ -503,7 +504,7 @@ void GUIEngine::drawFooter(video::IVideoDriver* driver)
 		rect += v2s32(screensize.Width/2,screensize.Height-footersize.Y);
 		rect -= v2s32(footersize.X/2, 0);
 
-		driver->draw2DImage(texture, rect,
+		draw2DImageFilterScaled(driver, texture, rect,
 			core::rect<s32>(core::position2d<s32>(0,0),
 			core::dimension2di(texture->getOriginalSize())),
 			NULL, NULL, true);
diff --git a/src/guiFormSpecMenu.cpp b/src/guiFormSpecMenu.cpp
index 11360a0fc..56729846e 100644
--- a/src/guiFormSpecMenu.cpp
+++ b/src/guiFormSpecMenu.cpp
@@ -51,6 +51,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "util/hex.h"
 #include "util/numeric.h"
 #include "util/string.h" // for parseColorString()
+#include "guiscalingfilter.h"
 
 #define MY_CHECKPOS(a,b)													\
 	if (v_pos.size() != 2) {												\
@@ -1307,8 +1308,8 @@ void GUIFormSpecMenu::parseImageButton(parserData* data,std::string element,
 		}
 
 		e->setUseAlphaChannel(true);
-		e->setImage(texture);
-		e->setPressedImage(pressed_texture);
+		e->setImage(guiScalingImageButton(Environment->getVideoDriver(), texture, geom.X, geom.Y));
+		e->setPressedImage(guiScalingImageButton(Environment->getVideoDriver(), pressed_texture, geom.X, geom.Y));
 		e->setScaleImage(true);
 		e->setNotClipped(noclip);
 		e->setDrawBorder(drawborder);
@@ -1452,8 +1453,8 @@ void GUIFormSpecMenu::parseItemImageButton(parserData* data,std::string element)
 		}
 
 		e->setUseAlphaChannel(true);
-		e->setImage(texture);
-		e->setPressedImage(texture);
+		e->setImage(guiScalingImageButton(Environment->getVideoDriver(), texture, geom.X, geom.Y));
+		e->setPressedImage(guiScalingImageButton(Environment->getVideoDriver(), texture, geom.X, geom.Y));
 		e->setScaleImage(true);
 		spec.ftype = f_Button;
 		rect+=data->basepos-padding;
@@ -2283,7 +2284,7 @@ void GUIFormSpecMenu::drawMenu()
 
 			const video::SColor color(255,255,255,255);
 			const video::SColor colors[] = {color,color,color,color};
-			driver->draw2DImage(texture, rect,
+			draw2DImageFilterScaled(driver, texture, rect,
 				core::rect<s32>(core::position2d<s32>(0,0),
 						core::dimension2di(texture->getOriginalSize())),
 				NULL/*&AbsoluteClippingRect*/, colors, true);
@@ -2333,7 +2334,7 @@ void GUIFormSpecMenu::drawMenu()
 			core::rect<s32> rect = imgrect + spec.pos;
 			const video::SColor color(255,255,255,255);
 			const video::SColor colors[] = {color,color,color,color};
-			driver->draw2DImage(texture, rect,
+			draw2DImageFilterScaled(driver, texture, rect,
 				core::rect<s32>(core::position2d<s32>(0,0),img_origsize),
 				NULL/*&AbsoluteClippingRect*/, colors, true);
 		}
@@ -2362,7 +2363,7 @@ void GUIFormSpecMenu::drawMenu()
 		core::rect<s32> rect = imgrect + spec.pos;
 		const video::SColor color(255,255,255,255);
 		const video::SColor colors[] = {color,color,color,color};
-		driver->draw2DImage(texture, rect,
+		draw2DImageFilterScaled(driver, texture, rect,
 			core::rect<s32>(core::position2d<s32>(0,0),
 					core::dimension2di(texture->getOriginalSize())),
 			NULL/*&AbsoluteClippingRect*/, colors, true);
diff --git a/src/guiTable.cpp b/src/guiTable.cpp
index a7a53f581..6dcd115b0 100644
--- a/src/guiTable.cpp
+++ b/src/guiTable.cpp
@@ -36,6 +36,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "main.h"
 #include "settings.h" // for settings
 #include "porting.h" // for dpi
+#include "guiscalingfilter.h"
 
 /*
 	GUITable
diff --git a/src/guiscalingfilter.cpp b/src/guiscalingfilter.cpp
new file mode 100644
index 000000000..92dadeaec
--- /dev/null
+++ b/src/guiscalingfilter.cpp
@@ -0,0 +1,160 @@
+/*
+Copyright (C) 2015 Aaron Suen <warr1024@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "guiscalingfilter.h"
+#include "imagefilters.h"
+#include "settings.h"
+#include "main.h"		// for g_settings
+#include "util/numeric.h"
+#include <stdio.h>
+
+/* Maintain a static cache to store the images that correspond to textures
+ * in a format that's manipulable by code.  Some platforms exhibit issues
+ * converting textures back into images repeatedly, and some don't even
+ * allow it at all.
+ */
+std::map<io::path, video::IImage *> imgCache;
+
+/* Maintain a static cache of all pre-scaled textures.  These need to be
+ * cleared as well when the cached images.
+ */
+std::map<io::path, video::ITexture *> txrCache;
+
+/* Manually insert an image into the cache, useful to avoid texture-to-image
+ * conversion whenever we can intercept it.
+ */
+void guiScalingCache(io::path key, video::IVideoDriver *driver, video::IImage *value) {
+	if (!g_settings->getBool("gui_scaling_filter"))
+		return;
+	video::IImage *copied = driver->createImage(value->getColorFormat(),
+			value->getDimension());
+	value->copyTo(copied);
+	imgCache[key] = copied;
+}
+
+// Manually clear the cache, e.g. when switching to different worlds.
+void guiScalingCacheClear(video::IVideoDriver *driver) {
+	for (std::map<io::path, video::IImage *>::iterator it = imgCache.begin();
+			it != imgCache.end(); it++) {
+		if (it->second != NULL)
+			it->second->drop();
+	}
+	imgCache.clear();
+	for (std::map<io::path, video::ITexture *>::iterator it = txrCache.begin();
+			it != txrCache.end(); it++) {
+		if (it->second != NULL)
+			driver->removeTexture(it->second);
+	}
+	txrCache.clear();
+}
+
+/* Get a cached, high-quality pre-scaled texture for display purposes.  If the
+ * texture is not already cached, attempt to create it.  Returns a pre-scaled texture,
+ * or the original texture if unable to pre-scale it.
+ */
+video::ITexture *guiScalingResizeCached(video::IVideoDriver *driver, video::ITexture *src,
+		const core::rect<s32> &srcrect, const core::rect<s32> &destrect) {
+
+	if (!g_settings->getBool("gui_scaling_filter"))
+		return src;
+
+	// Calculate scaled texture name.
+	char rectstr[200];
+	sprintf(rectstr, "%d:%d:%d:%d:%d:%d",
+		srcrect.UpperLeftCorner.X,
+		srcrect.UpperLeftCorner.Y,
+		srcrect.getWidth(),
+		srcrect.getHeight(),
+		destrect.getWidth(),
+		destrect.getHeight());
+	io::path origname = src->getName().getPath();
+	io::path scalename = origname + "@guiScalingFilter:" + rectstr;
+
+	// Search for existing scaled texture.
+	video::ITexture *scaled = txrCache[scalename];
+	if (scaled)
+		return scaled;
+
+	// Try to find the texture converted to an image in the cache.
+	// If the image was not found, try to extract it from the texture.
+	video::IImage* srcimg = imgCache[origname];
+	if (srcimg == NULL) {
+		if (!g_settings->getBool("gui_scaling_filter_txr2img"))
+			return src;
+		srcimg = driver->createImageFromData(src->getColorFormat(),
+			src->getSize(), src->lock(), false);
+		src->unlock();
+		imgCache[origname] = srcimg;
+	}
+
+	// Create a new destination image and scale the source into it.
+	imageCleanTransparent(srcimg, 0);
+	video::IImage *destimg = driver->createImage(src->getColorFormat(),
+			core::dimension2d<u32>((u32)destrect.getWidth(),
+			(u32)destrect.getHeight()));
+	imageScaleNNAA(srcimg, srcrect, destimg);
+
+#ifdef __ANDROID__
+	// Android is very picky about textures being powers of 2, so expand
+	// the image dimensions to the next power of 2, if necessary, for
+	// that platform.
+	video::IImage *po2img = driver->createImage(src->getColorFormat(),
+			core::dimension2d<u32>(npot2((u32)destrect.getWidth()),
+			npot2((u32)destrect.getHeight())));
+	po2img->fill(video::SColor(0, 0, 0, 0));
+	destimg->copyTo(po2img);
+	destimg->drop();
+	destimg = po2img;
+#endif
+
+	// Convert the scaled image back into a texture.
+	scaled = driver->addTexture(scalename, destimg, NULL);
+	destimg->drop();
+	txrCache[scalename] = scaled;
+
+	return scaled;
+}
+
+/* Convenience wrapper for guiScalingResizeCached that accepts parameters that
+ * are available at GUI imagebutton creation time.
+ */
+video::ITexture *guiScalingImageButton(video::IVideoDriver *driver, video::ITexture *src,
+		s32 width, s32 height) {
+	return guiScalingResizeCached(driver, src,
+		core::rect<s32>(0, 0, src->getSize().Width, src->getSize().Height),
+		core::rect<s32>(0, 0, width, height));
+}
+
+/* Replacement for driver->draw2DImage() that uses the high-quality pre-scaled
+ * texture, if configured.
+ */
+void draw2DImageFilterScaled(video::IVideoDriver *driver, video::ITexture *txr,
+		const core::rect<s32> &destrect, const core::rect<s32> &srcrect,
+		const core::rect<s32> *cliprect, const video::SColor *const colors,
+		bool usealpha) {
+
+	// Attempt to pre-scale image in software in high quality.
+	video::ITexture *scaled = guiScalingResizeCached(driver, txr, srcrect, destrect);
+
+	// Correct source rect based on scaled image.
+	const core::rect<s32> mysrcrect = (scaled != txr)
+		? core::rect<s32>(0, 0, destrect.getWidth(), destrect.getHeight())
+		: srcrect;
+
+	driver->draw2DImage(scaled, destrect, mysrcrect, cliprect, colors, usealpha);
+}
diff --git a/src/guiscalingfilter.h b/src/guiscalingfilter.h
new file mode 100644
index 000000000..768fe8d52
--- /dev/null
+++ b/src/guiscalingfilter.h
@@ -0,0 +1,52 @@
+/*
+Copyright (C) 2015 Aaron Suen <warr1024@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+#ifndef _GUI_SCALING_FILTER_H_
+#define _GUI_SCALING_FILTER_H_
+
+#include "irrlichttypes_extrabloated.h"
+
+/* Manually insert an image into the cache, useful to avoid texture-to-image
+ * conversion whenever we can intercept it.
+ */
+void guiScalingCache(io::path key, video::IVideoDriver *driver, video::IImage *value);
+
+// Manually clear the cache, e.g. when switching to different worlds.
+void guiScalingCacheClear(video::IVideoDriver *driver);
+
+/* Get a cached, high-quality pre-scaled texture for display purposes.  If the
+ * texture is not already cached, attempt to create it.  Returns a pre-scaled texture,
+ * or the original texture if unable to pre-scale it.
+ */
+video::ITexture *guiScalingResizeCached(video::IVideoDriver *driver, video::ITexture *src,
+		const core::rect<s32> &srcrect, const core::rect<s32> &destrect);
+
+/* Convenience wrapper for guiScalingResizeCached that accepts parameters that
+ * are available at GUI imagebutton creation time.
+ */
+video::ITexture *guiScalingImageButton(video::IVideoDriver *driver, video::ITexture *src,
+		s32 width, s32 height);
+
+/* Replacement for driver->draw2DImage() that uses the high-quality pre-scaled
+ * texture, if configured.
+ */
+void draw2DImageFilterScaled(video::IVideoDriver *driver, video::ITexture *txr,
+		const core::rect<s32> &destrect, const core::rect<s32> &srcrect,
+		const core::rect<s32> *cliprect = 0, const video::SColor *const colors = 0,
+		bool usealpha = false);
+
+#endif
diff --git a/src/hud.cpp b/src/hud.cpp
index aabaa066c..0b34a7b5b 100644
--- a/src/hud.cpp
+++ b/src/hud.cpp
@@ -32,6 +32,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "camera.h"
 #include "porting.h"
 #include "fontengine.h"
+#include "guiscalingfilter.h"
 #include <IGUIStaticText.h>
 
 #ifdef HAVE_TOUCHSCREENGUI
@@ -94,7 +95,7 @@ void Hud::drawItem(const ItemStack &item, const core::rect<s32>& rect, bool sele
 				imgrect2.LowerRightCorner.Y += (m_padding*2);
 					video::ITexture *texture = tsrc->getTexture(hotbar_selected_image);
 					core::dimension2di imgsize(texture->getOriginalSize());
-				driver->draw2DImage(texture, imgrect2,
+				draw2DImageFilterScaled(driver, texture, imgrect2,
 						core::rect<s32>(core::position2d<s32>(0,0), imgsize),
 						NULL, hbar_colors, true);
 			} else {
@@ -200,7 +201,7 @@ void Hud::drawItems(v2s32 upperleftpos, s32 itemcount, s32 offset,
 		core::rect<s32> rect2 = imgrect2 + pos;
 		video::ITexture *texture = tsrc->getTexture(hotbar_image);
 		core::dimension2di imgsize(texture->getOriginalSize());
-		driver->draw2DImage(texture, rect2,
+		draw2DImageFilterScaled(driver, texture, rect2,
 			core::rect<s32>(core::position2d<s32>(0,0), imgsize),
 			NULL, hbar_colors, true);
 	}
@@ -266,7 +267,7 @@ void Hud::drawLuaElements(v3s16 camera_offset) {
 				             (e->align.Y - 1.0) * dstsize.Y / 2);
 				core::rect<s32> rect(0, 0, dstsize.X, dstsize.Y);
 				rect += pos + offset + v2s32(e->offset.X, e->offset.Y);
-				driver->draw2DImage(texture, rect,
+				draw2DImageFilterScaled(driver, texture, rect,
 					core::rect<s32>(core::position2d<s32>(0,0), imgsize),
 					NULL, colors, true);
 				break; }
@@ -378,7 +379,7 @@ void Hud::drawStatbar(v2s32 pos, u16 corner, u16 drawdir, std::string texture,
 		core::rect<s32> dstrect(0,0, dstd.Width, dstd.Height);
 
 		dstrect += p;
-		driver->draw2DImage(stat_texture, dstrect, srcrect, NULL, colors, true);
+		draw2DImageFilterScaled(driver, stat_texture, dstrect, srcrect, NULL, colors, true);
 		p += steppos;
 	}
 
@@ -388,7 +389,7 @@ void Hud::drawStatbar(v2s32 pos, u16 corner, u16 drawdir, std::string texture,
 		core::rect<s32> dstrect(0,0, dstd.Width / 2, dstd.Height);
 
 		dstrect += p;
-		driver->draw2DImage(stat_texture, dstrect, srcrect, NULL, colors, true);
+		draw2DImageFilterScaled(driver, stat_texture, dstrect, srcrect, NULL, colors, true);
 	}
 }
 
@@ -502,7 +503,7 @@ void drawItemStack(video::IVideoDriver *driver,
 	{
 		const video::SColor color(255,255,255,255);
 		const video::SColor colors[] = {color,color,color,color};
-		driver->draw2DImage(texture, rect,
+		draw2DImageFilterScaled(driver, texture, rect,
 			core::rect<s32>(core::position2d<s32>(0,0),
 			core::dimension2di(texture->getOriginalSize())),
 			clip, colors, true);
diff --git a/src/imagefilters.cpp b/src/imagefilters.cpp
new file mode 100644
index 000000000..a995e98d6
--- /dev/null
+++ b/src/imagefilters.cpp
@@ -0,0 +1,172 @@
+/*
+Copyright (C) 2015 Aaron Suen <warr1024@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "imagefilters.h"
+#include "util/numeric.h"
+#include <math.h>
+
+/* Fill in RGB values for transparent pixels, to correct for odd colors
+ * appearing at borders when blending.  This is because many PNG optimizers
+ * like to discard RGB values of transparent pixels, but when blending then
+ * with non-transparent neighbors, their RGB values will shpw up nonetheless.
+ *
+ * This function modifies the original image in-place.
+ *
+ * Parameter "threshold" is the alpha level below which pixels are considered
+ * transparent.  Should be 127 for 3d where alpha is threshold, but 0 for
+ * 2d where alpha is blended.
+ */
+void imageCleanTransparent(video::IImage *src, u32 threshold) {
+
+	core::dimension2d<u32> dim = src->getDimension();
+
+	// Walk each pixel looking for fully transparent ones.
+	// Note: loop y around x for better cache locality.
+	for (u32 ctry = 0; ctry < dim.Height; ctry++)
+	for (u32 ctrx = 0; ctrx < dim.Width; ctrx++) {
+
+		// Ignore opaque pixels.
+		irr::video::SColor c = src->getPixel(ctrx, ctry);
+		if (c.getAlpha() > threshold)
+			continue;
+
+		// Sample size and total weighted r, g, b values.
+		u32 ss = 0, sr = 0, sg = 0, sb = 0;
+
+		// Walk each neighbor pixel (clipped to image bounds).
+		for (u32 sy = (ctry < 1) ? 0 : (ctry - 1);
+				sy <= (ctry + 1) && sy < dim.Height; sy++)
+		for (u32 sx = (ctrx < 1) ? 0 : (ctrx - 1);
+				sx <= (ctrx + 1) && sx < dim.Width; sx++) {
+
+			// Ignore transparent pixels.
+			irr::video::SColor d = src->getPixel(sx, sy);
+			if (d.getAlpha() <= threshold)
+				continue;
+
+			// Add RGB values weighted by alpha.
+			u32 a = d.getAlpha();
+			ss += a;
+			sr += a * d.getRed();
+			sg += a * d.getGreen();
+			sb += a * d.getBlue();
+		}
+
+		// If we found any neighbor RGB data, set pixel to average
+		// weighted by alpha.
+		if (ss > 0) {
+			c.setRed(sr / ss);
+			c.setGreen(sg / ss);
+			c.setBlue(sb / ss);
+			src->setPixel(ctrx, ctry, c);
+		}
+	}
+}
+
+/* Scale a region of an image into another image, using nearest-neighbor with
+ * anti-aliasing; treat pixels as crisp rectangles, but blend them at boundaries
+ * to prevent non-integer scaling ratio artifacts.  Note that this may cause
+ * some blending at the edges where pixels don't line up perfectly, but this
+ * filter is designed to produce the most accurate results for both upscaling
+ * and downscaling.
+ */
+void imageScaleNNAA(video::IImage *src, const core::rect<s32> &srcrect, video::IImage *dest) {
+
+	double sx, sy, minsx, maxsx, minsy, maxsy, area, ra, ga, ba, aa, pw, ph, pa;
+	u32 dy, dx;
+	video::SColor pxl;
+
+	// Cache rectsngle boundaries.
+	double sox = srcrect.UpperLeftCorner.X * 1.0;
+	double soy = srcrect.UpperLeftCorner.Y * 1.0;
+	double sw = srcrect.getWidth() * 1.0;
+	double sh = srcrect.getHeight() * 1.0;
+
+	// Walk each destination image pixel.
+	// Note: loop y around x for better cache locality.
+	core::dimension2d<u32> dim = dest->getDimension();
+	for (dy = 0; dy < dim.Height; dy++)
+	for (dx = 0; dx < dim.Width; dx++) {
+
+		// Calculate floating-point source rectangle bounds.
+		// Do some basic clipping, and for mirrored/flipped rects,
+		// make sure min/max are in the right order.
+		minsx = sox + (dx * sw / dim.Width);
+		minsx = rangelim(minsx, 0, sw);
+		maxsx = minsx + sw / dim.Width;
+		maxsx = rangelim(maxsx, 0, sw);
+		if (minsx > maxsx)
+			SWAP(double, minsx, maxsx);
+		minsy = soy + (dy * sh / dim.Height);
+		minsy = rangelim(minsy, 0, sh);
+		maxsy = minsy + sh / dim.Height;
+		maxsy = rangelim(maxsy, 0, sh);
+		if (minsy > maxsy)
+			SWAP(double, minsy, maxsy);
+
+		// Total area, and integral of r, g, b values over that area,
+		// initialized to zero, to be summed up in next loops.
+		area = 0;
+		ra = 0;
+		ga = 0;
+		ba = 0;
+		aa = 0;
+
+		// Loop over the integral pixel positions described by those bounds.
+		for (sy = floor(minsy); sy < maxsy; sy++)
+		for (sx = floor(minsx); sx < maxsx; sx++) {
+
+			// Calculate width, height, then area of dest pixel
+			// that's covered by this source pixel.
+			pw = 1;
+			if (minsx > sx)
+				pw += sx - minsx;
+			if (maxsx < (sx + 1))
+				pw += maxsx - sx - 1;
+			ph = 1;
+			if (minsy > sy)
+				ph += sy - minsy;
+			if (maxsy < (sy + 1))
+				ph += maxsy - sy - 1;
+			pa = pw * ph;
+
+			// Get source pixel and add it to totals, weighted
+			// by covered area and alpha.
+			pxl = src->getPixel((u32)sx, (u32)sy);
+			area += pa;
+			ra += pa * pxl.getRed();
+			ga += pa * pxl.getGreen();
+			ba += pa * pxl.getBlue();
+			aa += pa * pxl.getAlpha();
+		}
+
+		// Set the destination image pixel to the average color.
+		if (area > 0) {
+			pxl.setRed(ra / area + 0.5);
+			pxl.setGreen(ga / area + 0.5);
+			pxl.setBlue(ba / area + 0.5);
+			pxl.setAlpha(aa / area + 0.5);
+		} else {
+			pxl.setRed(0);
+			pxl.setGreen(0);
+			pxl.setBlue(0);
+			pxl.setAlpha(0);
+		}
+		dest->setPixel(dx, dy, pxl);
+	}
+}
diff --git a/src/imagefilters.h b/src/imagefilters.h
new file mode 100644
index 000000000..28787027f
--- /dev/null
+++ b/src/imagefilters.h
@@ -0,0 +1,46 @@
+/*
+Copyright (C) 2015 Aaron Suen <warr1024@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#ifndef _IMAGE_FILTERS_H_
+#define _IMAGE_FILTERS_H_
+
+#include "irrlichttypes_extrabloated.h"
+
+/* Fill in RGB values for transparent pixels, to correct for odd colors
+ * appearing at borders when blending.  This is because many PNG optimizers
+ * like to discard RGB values of transparent pixels, but when blending then
+ * with non-transparent neighbors, their RGB values will shpw up nonetheless.
+ *
+ * This function modifies the original image in-place.
+ *
+ * Parameter "threshold" is the alpha level below which pixels are considered
+ * transparent.  Should be 127 for 3d where alpha is threshold, but 0 for
+ * 2d where alpha is blended.
+ */
+void imageCleanTransparent(video::IImage *src, u32 threshold);
+
+/* Scale a region of an image into another image, using nearest-neighbor with
+ * anti-aliasing; treat pixels as crisp rectangles, but blend them at boundaries
+ * to prevent non-integer scaling ratio artifacts.  Note that this may cause
+ * some blending at the edges where pixels don't line up perfectly, but this
+ * filter is designed to produce the most accurate results for both upscaling
+ * and downscaling.
+ */
+void imageScaleNNAA(video::IImage *src, const core::rect<s32> &srcrect, video::IImage *dest);
+
+#endif
diff --git a/src/touchscreengui.cpp b/src/touchscreengui.cpp
index 2d489c1f8..f5868133f 100644
--- a/src/touchscreengui.cpp
+++ b/src/touchscreengui.cpp
@@ -25,6 +25,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "gettime.h"
 #include "util/numeric.h"
 #include "porting.h"
+#include "guiscalingfilter.h"
 
 #include <iostream>
 #include <algorithm>
@@ -130,15 +131,23 @@ TouchScreenGUI::TouchScreenGUI(IrrlichtDevice *device, IEventReceiver* receiver)
 	m_screensize = m_device->getVideoDriver()->getScreenSize();
 }
 
-void TouchScreenGUI::loadButtonTexture(button_info* btn, const char* path)
+void TouchScreenGUI::loadButtonTexture(button_info* btn, const char* path, rect<s32> button_rect)
 {
 	unsigned int tid;
-	video::ITexture *texture = m_texturesource->getTexture(path,&tid);
+	video::ITexture *texture = guiScalingImageButton(m_device->getVideoDriver(),
+		m_texturesource->getTexture(path, &tid), button_rect.getWidth(), button_rect.getHeight());
 	if (texture) {
 		btn->guibutton->setUseAlphaChannel(true);
-		btn->guibutton->setImage(texture);
-		btn->guibutton->setPressedImage(texture);
-		btn->guibutton->setScaleImage(true);
+		if (g_settings->getBool("gui_scaling_filter")) {
+			rect<s32> txr_rect = rect<s32>(0, 0, button_rect.getWidth(), button_rect.getHeight());
+			btn->guibutton->setImage(texture, txr_rect);
+			btn->guibutton->setPressedImage(texture, txr_rect);
+			btn->guibutton->setScaleImage(false);
+		} else {
+			btn->guibutton->setImage(texture);
+			btn->guibutton->setPressedImage(texture);
+			btn->guibutton->setScaleImage(true);
+		}
 		btn->guibutton->setDrawBorder(false);
 		btn->guibutton->setText(L"");
 		}
@@ -157,7 +166,7 @@ void TouchScreenGUI::initButton(touch_gui_button_id id, rect<s32> button_rect,
 	btn->immediate_release = immediate_release;
 	btn->ids.clear();
 
-	loadButtonTexture(btn,touchgui_button_imagenames[id]);
+	loadButtonTexture(btn,touchgui_button_imagenames[id], button_rect);
 }
 
 static int getMaxControlPadSize(float density) {
diff --git a/src/touchscreengui.h b/src/touchscreengui.h
index 2ded26a05..bb3231793 100644
--- a/src/touchscreengui.h
+++ b/src/touchscreengui.h
@@ -130,7 +130,7 @@ private:
 			float repeat_delay = BUTTON_REPEAT_DELAY);
 
 	/* load texture */
-	void loadButtonTexture(button_info* btn, const char* path);
+	void loadButtonTexture(button_info* btn, const char* path, rect<s32> button_rect);
 
 	struct id_status{
 		int id;
diff --git a/src/util/numeric.cpp b/src/util/numeric.cpp
index 2306976ec..4ddfede92 100644
--- a/src/util/numeric.cpp
+++ b/src/util/numeric.cpp
@@ -245,4 +245,3 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 
 	return true;
 }
-
diff --git a/src/util/numeric.h b/src/util/numeric.h
index a158a2eae..b4b841918 100644
--- a/src/util/numeric.h
+++ b/src/util/numeric.h
@@ -411,5 +411,16 @@ inline bool is_power_of_two(u32 n)
 	return n != 0 && (n & (n-1)) == 0;
 }
 
-#endif
+// Compute next-higher power of 2 efficiently, e.g. for power-of-2 texture sizes.
+// Public Domain: https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+inline u32 npot2(u32 orig) {
+	orig--;
+	orig |= orig >> 1;
+	orig |= orig >> 2;
+	orig |= orig >> 4;
+	orig |= orig >> 8;
+	orig |= orig >> 16;
+	return orig + 1;
+}
 
+#endif