Remove SDL_image and link against libpng directly

sc2/build/unix/build.config

@@ -28,7 +28,7 @@ uqm_requirements()
 
 	# Libraries always used
 	use_library SDL 1.2.8 || exit 1
-	use_library SDL_image || exit 1
+	use_library libpng || exit 1
 
 	case "$HOST_SYSTEM" in
 		WINSCW|ARMV5|GCCE)

sc2/build/unix/config_proginfo_host

@@ -110,6 +110,18 @@ esac
 LIB_SDL_image_VERSION=""
 
 
+### libpng ###
+LIB_libpng_NAME="libpng"
+# libpng generally integrates with pkg-config, but that also generally
+# only matters if we're building against a non-systemwide version. UQM
+# should not need to do that.
+#
+# To link against a static libpng, set LDFLAGS with an appropriate -L
+# argument before calling `build.sh uqm config`.
+LIB_libpng_CFLAGS=""
+LIB_libpng_LDFLAGS="-lpng"
+
+
 ### OpenAL ###
 LIB_openal_NAME="OpenAL"
 LIB_openal_CFLAGS=""

sc2/src/libs/graphics/sdl/Makeinfo

@@ -2,4 +2,4 @@ uqm_CFILES="opengl.c palette.c primitives.c pure.c sdl_common.c
 		scalers.c 2xscalers.c
 		2xscalers_mmx.c 2xscalers_sse.c 2xscalers_3dnow.c
 		nearest2x.c bilinear2x.c biadv2x.c triscan2x.c hq2x.c
-		canvas.c sdluio.c rotozoom.c"
+		canvas.c png2sdl.c sdluio.c rotozoom.c"

sc2/src/libs/graphics/sdl/png2sdl.c

@@ -0,0 +1,300 @@
+/*
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * This code is adapted from IMG_png.c in the SDL2_image library, which is
+ * available under the zlib license and is (c) 1997-2019 Sam Lantinga. The
+ * code itself is credited to Philippe Lavoie as the original author. It
+ * also shares some heritage with libpng's own example.c file, and
+ * ultimately inherits the GPL2+ license from the rest of UQM.
+ *
+ * Differences from SDL2_image are:
+ *  - It is PNG-only
+ *  - It directly links the relevant version of libpng at compile time
+ *  - It always uses libpng and will never forward to alternative
+ *    libraries such as ImageIO.framework. This means that palette
+ *    information will always be preserved, as UQM requires.
+ *  - It locks the surface as the API demands rather than using
+ *    volatility markers
+ *  - Palette assignment is done through the API rather than by
+ *    directly editing the format contents
+ */
+
+#include "png2sdl.h"
+#include <png.h>
+
+/* Link function between SDL_RWops and PNG's data source */
+static void
+png_read_data(png_structp ctx, png_bytep area, png_size_t size)
+{
+	SDL_RWops *src = (SDL_RWops *)png_get_io_ptr (ctx);
+	SDL_RWread (src, area, size, 1);
+}
+
+SDL_Surface *
+TFB_png_to_sdl (SDL_RWops *src)
+{
+	Sint64 start;
+	const char *error;
+	SDL_Surface *surface;
+	png_structp png_ptr;
+	png_infop info_ptr;
+	png_uint_32 width, height;
+	int bit_depth, color_type, interlace_type, num_channels;
+	Uint32 Rmask, Gmask, Bmask, Amask;
+	png_bytep *row_pointers;
+	int row, i;
+	int ckey = -1;
+	png_color_16 *transv;
+
+	if (!src)
+	{
+		/* The error message has been set in SDL_RWFromFile */
+		return NULL;
+	}
+	start = SDL_RWtell (src);
+
+	/* Initialize the data we will clean up when we're done */
+	error = NULL;
+	png_ptr = NULL;
+	info_ptr = NULL;
+	row_pointers = NULL;
+	surface = NULL;
+
+	/* Create the PNG loading context structure */
+	png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING,
+			NULL, NULL, NULL);
+	if (png_ptr == NULL)
+	{
+		error = "Couldn't allocate memory for PNG file";
+		goto done;
+	}
+
+	/* Allocate/initialize the memory for image information */
+	info_ptr = png_create_info_struct (png_ptr);
+	if (info_ptr == NULL)
+	{
+		error = "Couldn't create image information for PNG file";
+		goto done;
+	}
+
+	/* Set error handling */
+	if (setjmp (png_jmpbuf (png_ptr)))
+	{
+		error = "Error reading the PNG file.";
+		goto done;
+	}
+
+	/* Set up the input control */
+	png_set_read_fn (png_ptr, src, png_read_data);
+
+	/* Read PNG header info */
+	png_read_info (png_ptr, info_ptr);
+	png_get_IHDR (png_ptr, info_ptr, &width, &height, &bit_depth,
+			&color_type, &interlace_type, NULL, NULL);
+
+
+	/* Configure the decode based on what we know of the image
+	 * already: strip 16 bit color down to 8 bit, automatically
+	 * deinterlace, expand grayscale images or those with more
+	 * than one transparent color or any translucent colors into
+	 * full RGB or RGBA, and expand 1, 2, or 4-bpp paletted
+	 * images to 8bpp. */
+	png_set_strip_16 (png_ptr);
+	png_set_interlace_handling (png_ptr);
+	png_set_packing (png_ptr);
+	if (color_type == PNG_COLOR_TYPE_GRAY)
+	{
+		png_set_expand (png_ptr);
+	}
+	if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
+	{
+		int num_trans;
+		Uint8 *trans;
+		png_get_tRNS (png_ptr, info_ptr, &trans, &num_trans, &transv);
+		if (color_type == PNG_COLOR_TYPE_PALETTE)
+		{
+			/* Check if all tRNS entries are opaque except one */
+			int j, t = -1;
+			for (j = 0; j < num_trans; j++)
+			{
+				if (trans[j] == 0)
+				{
+					if (t >= 0)
+					{
+						break;
+					}
+					t = j;
+				}
+				else if (trans[j] != 255)
+				{
+					break;
+				}
+			}
+			if (j == num_trans)
+			{
+				/* exactly one transparent index */
+				ckey = t;
+			}
+			else
+			{
+				/* more than one transparent index, or translucency */
+				png_set_expand (png_ptr);
+			}
+		}
+		else
+		{
+			ckey = 0; /* actual value will be set later */
+		}
+	}
+
+	if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+	{
+		png_set_gray_to_rgb (png_ptr);
+	}
+
+	/* Register our changes with the reading machinery and refresh
+	 * our ancillary data about the image */
+	png_read_update_info (png_ptr, info_ptr);
+	png_get_IHDR (png_ptr, info_ptr, &width, &height, &bit_depth,
+			&color_type, &interlace_type, NULL, NULL);
+
+	/* Allocate the SDL surface to hold the image */
+	Rmask = Gmask = Bmask = Amask = 0;
+	num_channels = png_get_channels (png_ptr, info_ptr);
+	if (num_channels >= 3)
+	{
+#if SDL_BYTEORDER == SDL_LIL_ENDIAN
+		Rmask = 0x000000FF;
+		Gmask = 0x0000FF00;
+		Bmask = 0x00FF0000;
+		Amask = (num_channels == 4) ? 0xFF000000 : 0;
+#else
+		int s = (num_channels == 4) ? 0 : 8;
+		Rmask = 0xFF000000 >> s;
+		Gmask = 0x00FF0000 >> s;
+		Bmask = 0x0000FF00 >> s;
+		Amask = 0x000000FF >> s;
+#endif
+	}
+	surface = SDL_CreateRGBSurface (SDL_SWSURFACE, width, height,
+			bit_depth * num_channels,
+			Rmask, Gmask, Bmask, Amask);
+	if (surface == NULL)
+	{
+		error = SDL_GetError ();
+		goto done;
+	}
+
+	if (ckey != -1)
+	{
+		if (color_type != PNG_COLOR_TYPE_PALETTE)
+		{
+			/* FIXME: Should these be truncated or shifted down? */
+			ckey = SDL_MapRGB(surface->format,
+					(Uint8)transv->red,
+					(Uint8)transv->green,
+					(Uint8)transv->blue);
+		}
+#if SDL_MAJOR_VERSION >= 2
+		SDL_SetColorKey (surface, SDL_TRUE, ckey);
+#else
+		SDL_SetColorKey (surface, SDL_SRCCOLORKEY, ckey);
+#endif
+	}
+
+	SDL_LockSurface (surface);
+	/* Create the array of pointers to image data */
+	row_pointers = (png_bytep *)SDL_malloc (sizeof (png_bytep) * height);
+	if (!row_pointers)
+	{
+		error = "Out of memory";
+		goto done;
+	}
+	for (row = 0; row < (int)height; row++)
+	{
+		row_pointers[row] = (png_bytep)
+			(Uint8 *)surface->pixels + row*surface->pitch;
+	}
+
+	/* Read the entire image in one go */
+	png_read_image (png_ptr, row_pointers);
+	SDL_UnlockSurface (surface);
+
+	/* and we're done!  (png_read_end() can be omitted if no
+	 * processing of post-IDAT text/time/etc. is desired)
+	 * In some cases it can't read PNGs created by some popular
+	 * programs (ACDSEE), we do not want to process comments, so
+	 * we omit png_read_end */
+
+	/* Load the palette, if any */
+	if (surface->format->palette)
+	{
+		SDL_Color palette[256];
+		int png_num_palette;
+		png_colorp png_palette;
+		png_get_PLTE (png_ptr, info_ptr, &png_palette, &png_num_palette);
+		if (color_type == PNG_COLOR_TYPE_GRAY)
+		{
+			png_num_palette = 256;
+			for (i = 0; i < 256; i++)
+			{
+				palette[i].r = (Uint8)i;
+				palette[i].g = (Uint8)i;
+				palette[i].b = (Uint8)i;
+			}
+		}
+		else if (png_num_palette > 0)
+		{
+			for (i = 0; i < png_num_palette; ++i)
+			{
+				palette[i].b = png_palette[i].blue;
+				palette[i].g = png_palette[i].green;
+				palette[i].r = png_palette[i].red;
+			}
+		}
+#if SDL_MAJOR_VERSION >= 2
+		SDL_SetPaletteColors (surface->format->palette, palette,
+				0, png_num_palette);
+#else
+		SDL_SetPalette (surface, SDL_LOGPAL, palette,
+				0, png_num_palette);
+#endif
+	}
+
+done:	/* Clean up and return */
+	if (png_ptr)
+	{
+		png_destroy_read_struct (&png_ptr,
+				info_ptr ? &info_ptr : (png_infopp)0,
+				(png_infopp)0);
+	}
+	if (row_pointers)
+	{
+		SDL_free (row_pointers);
+	}
+	if (error)
+	{
+		SDL_RWseek(src, start, RW_SEEK_SET);
+		if (surface)
+		{
+			SDL_FreeSurface (surface);
+			surface = NULL;
+		}
+		fprintf (stderr, "%s", error);
+	}
+	return surface;
+}

sc2/src/libs/graphics/sdl/png2sdl.h

@@ -0,0 +1,24 @@
+/*
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef PNG2SDL_H_
+#define PNG2SDL_H_
+
+#include <SDL.h>
+
+SDL_Surface *TFB_png_to_sdl (SDL_RWops *src);
+
+#endif

sc2/src/libs/graphics/sdl/sdluio.c

@@ -21,8 +21,8 @@
 #include SDL_INCLUDE(SDL.h)
 #include SDL_INCLUDE(SDL_error.h)
 #include SDL_INCLUDE(SDL_rwops.h)
-#include SDL_IMAGE_INCLUDE(SDL_image.h)
 #include "libs/memlib.h"
+#include "png2sdl.h"
 #include <errno.h>
 #include <string.h>
 
@@ -44,7 +44,7 @@ SDL_Surface *
 sdluio_loadImage (uio_DirHandle *dir, const char *fileName) {
 	uio_Stream *stream;
 	SDL_RWops *rwops;
-	SDL_Surface *result;
+	SDL_Surface *result = NULL;
 
 	stream = uio_fopen (dir, fileName, "rb");
 	if (stream == NULL)
@@ -54,7 +54,10 @@ sdluio_loadImage (uio_DirHandle *dir, const char *fileName) {
 		return NULL;
 	}
 	rwops = sdluio_makeRWops (stream);
-	result = IMG_Load_RW (rwops, 1);
+	if (rwops) {
+		result = TFB_png_to_sdl (rwops);
+		SDL_RWclose (rwops);
+	}
 	return result;
 }