diff --git a/src/heightmap.cpp b/src/heightmap.cpp
new file mode 100644
--- /dev/null
+++ b/src/heightmap.cpp
@@ -0,0 +1,459 @@
+/* $Id$ */
+
+#include "stdafx.h"
+#include "openttd.h"
+#include "variables.h"
+#include "functions.h"
+#include "heightmap.h"
+#include "clear_map.h"
+#include "table/strings.h"
+#include "void_map.h"
+#include "debug.h"
+#include "gfx.h"
+#include "gui.h"
+#include "saveload.h"
+#include "bmp.h"
+
+/**
+ * Convert RGB colors to Grayscale using 29.9% Red, 58.7% Green, 11.4% Blue
+ *  (average luminosity formula) -- Dalestan
+ * This in fact is the NTSC Color Space -- TrueLight
+ */
+static inline byte RGBToGrayscale(byte red, byte green, byte blue)
+{
+	/* To avoid doubles and stuff, multiple it with a total of 65536 (16bits), then
+	 *  divide by it to normalize the value to a byte again. */
+	return ((red * 19595) + (green * 38470) + (blue * 7471)) / 65536;
+}
+
+
+#ifdef WITH_PNG
+
+#include "png.h"
+
+/**
+ * The PNG Heightmap loader.
+ */
+static void ReadHeightmapPNGImageData(byte *map, png_structp png_ptr, png_infop info_ptr)
+{
+	uint x, y;
+	byte gray_palette[256];
+	png_bytep *row_pointers = NULL;
+
+	/* Get palette and convert it to grayscale */
+	if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) {
+		int i;
+		int palette_size;
+		png_color *palette;
+		bool all_gray = true;
+
+		png_get_PLTE(png_ptr, info_ptr, &palette, &palette_size);
+		for (i = 0; i < palette_size && (palette_size != 16 || all_gray); i++) {
+			all_gray &= palette[i].red == palette[i].green && palette[i].red == palette[i].blue;
+			gray_palette[i] = RGBToGrayscale(palette[i].red, palette[i].green, palette[i].blue);
+		}
+
+		/**
+		 * For a non-gray palette of size 16 we assume that
+		 * the order of the palette determines the height;
+		 * the first entry is the sea (level 0), the second one
+		 * level 1, etc.
+		 */
+		if (palette_size == 16 && !all_gray) {
+			for (i = 0; i < palette_size; i++) {
+				gray_palette[i] = 256 * i / palette_size;
+			}
+		}
+	}
+
+	row_pointers = png_get_rows(png_ptr, info_ptr);
+
+	/* Read the raw image data and convert in 8-bit grayscale */
+	for (x = 0; x < info_ptr->width; x++) {
+		for (y = 0; y < info_ptr->height; y++) {
+			byte *pixel = &map[y * info_ptr->width + x];
+			uint x_offset = x * info_ptr->channels;
+
+			if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) {
+				*pixel = gray_palette[row_pointers[y][x_offset]];
+			} else if (info_ptr->channels == 3) {
+				*pixel = RGBToGrayscale(row_pointers[y][x_offset + 0],
+						row_pointers[y][x_offset + 1], row_pointers[y][x_offset + 2]);
+			} else {
+				*pixel = row_pointers[y][x_offset];
+			}
+		}
+	}
+}
+
+/**
+ * Reads the heightmap and/or size of the heightmap from a PNG file.
+ * If map == NULL only the size of the PNG is read, otherwise a map
+ * with grayscale pixels is allocated and assigned to *map.
+ */
+static bool ReadHeightmapPNG(char *filename, uint *x, uint *y, byte **map)
+{
+	FILE *fp;
+	png_structp png_ptr = NULL;
+	png_infop info_ptr  = NULL;
+
+	fp = fopen(filename, "rb");
+	if (fp == NULL) {
+		ShowErrorMessage(STR_PNGMAP_ERR_FILE_NOT_FOUND, STR_PNGMAP_ERROR, 0, 0);
+		return false;
+	}
+
+	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+	if (png_ptr == NULL) {
+		ShowErrorMessage(STR_PNGMAP_ERR_MISC, STR_PNGMAP_ERROR, 0, 0);
+		fclose(fp);
+		return false;
+	}
+
+	info_ptr = png_create_info_struct(png_ptr);
+	if (info_ptr == NULL || setjmp(png_jmpbuf(png_ptr))) {
+		ShowErrorMessage(STR_PNGMAP_ERR_MISC, STR_PNGMAP_ERROR, 0, 0);
+		fclose(fp);
+		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		return false;
+	}
+
+	png_init_io(png_ptr, fp);
+
+	/* Allocate memory and read image, without alpha or 16-bit samples
+	 * (result is either 8-bit indexed/grayscale or 24-bit RGB) */
+	png_set_packing(png_ptr);
+	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_PACKING | PNG_TRANSFORM_STRIP_ALPHA | PNG_TRANSFORM_STRIP_16, NULL);
+
+	/* Maps of wrong color-depth are not used.
+	 * (this should have been taken care of by stripping alpha and 16-bit samples on load) */
+	if ((info_ptr->channels != 1) && (info_ptr->channels != 3) && (info_ptr->bit_depth != 8)) {
+		ShowErrorMessage(STR_PNGMAP_ERR_IMAGE_TYPE, STR_PNGMAP_ERROR, 0, 0);
+		fclose(fp);
+		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		return false;
+	}
+
+	if (map != NULL) {
+		*map = malloc(info_ptr->width * info_ptr->height * sizeof(byte));
+
+		if (*map == NULL) {
+			ShowErrorMessage(STR_PNGMAP_ERR_MISC, STR_PNGMAP_ERROR, 0, 0);
+			fclose(fp);
+			png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+			return false;
+		}
+
+		ReadHeightmapPNGImageData(*map, png_ptr, info_ptr);
+	}
+
+	*x = info_ptr->width;
+	*y = info_ptr->height;
+
+	fclose(fp);
+	png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+	return true;
+}
+
+#endif /* WITH_PNG */
+
+
+/**
+ * The BMP Heightmap loader.
+ */
+static void ReadHeightmapBMPImageData(byte *map, BmpInfo *info, BmpData *data)
+{
+	uint x, y;
+	byte gray_palette[256];
+
+	if (data->palette != NULL) {
+		uint i;
+		bool all_gray = true;
+
+		if (info->palette_size != 2) {
+			for (i = 0; i < info->palette_size && (info->palette_size != 16 || all_gray); i++) {
+				all_gray &= data->palette[i].r == data->palette[i].g && data->palette[i].r == data->palette[i].b;
+				gray_palette[i] = RGBToGrayscale(data->palette[i].r, data->palette[i].g, data->palette[i].b);
+			}
+
+			/**
+			 * For a non-gray palette of size 16 we assume that
+			 * the order of the palette determines the height;
+			 * the first entry is the sea (level 0), the second one
+			 * level 1, etc.
+			 */
+			if (info->palette_size == 16 && !all_gray) {
+				for (i = 0; i < info->palette_size; i++) {
+					gray_palette[i] = 256 * i / info->palette_size;
+				}
+			}
+		} else {
+			/**
+			 * For a palette of size 2 we assume that the order of the palette determines the height;
+			 * the first entry is the sea (level 0), the second one is the land (level 1)
+			 */
+			gray_palette[0] = 0;
+			gray_palette[1] = 16;
+		}
+	}
+
+	/* Read the raw image data and convert in 8-bit grayscale */
+	for (y = 0; y < info->height; y++) {
+		byte *pixel = &map[y * info->width];
+		byte *bitmap = &data->bitmap[y * info->width * (info->bpp == 24 ? 3 : 1)];
+
+		for (x = 0; x < info->width; x++) {
+			if (info->bpp != 24) {
+				*pixel++ = gray_palette[*bitmap++];
+			} else {
+				*pixel++ = RGBToGrayscale(*bitmap, *(bitmap + 1), *(bitmap + 2));
+				bitmap += 3;
+			}
+		}
+	}
+}
+
+/**
+ * Reads the heightmap and/or size of the heightmap from a BMP file.
+ * If map == NULL only the size of the BMP is read, otherwise a map
+ * with grayscale pixels is allocated and assigned to *map.
+ */
+static bool ReadHeightmapBMP(char *filename, uint *x, uint *y, byte **map)
+{
+	FILE *f;
+	BmpInfo info;
+	BmpData data;
+	BmpBuffer buffer;
+
+	f = fopen(filename, "rb");
+	if (f == NULL) {
+		ShowErrorMessage(STR_PNGMAP_ERR_FILE_NOT_FOUND, STR_BMPMAP_ERROR, 0, 0);
+		return false;
+	}
+
+	BmpInitializeBuffer(&buffer, f);
+
+	if (!BmpReadHeader(&buffer, &info, &data)) {
+		ShowErrorMessage(STR_BMPMAP_ERR_IMAGE_TYPE, STR_BMPMAP_ERROR, 0, 0);
+		fclose(f);
+		BmpDestroyData(&data);
+		return false;
+	}
+
+	if (map != NULL) {
+		if (!BmpReadBitmap(&buffer, &info, &data)) {
+			ShowErrorMessage(STR_BMPMAP_ERR_IMAGE_TYPE, STR_BMPMAP_ERROR, 0, 0);
+			fclose(f);
+			BmpDestroyData(&data);
+			return false;
+		}
+
+		*map = malloc(info.width * info.height * sizeof(byte));
+		if (*map == NULL) {
+			ShowErrorMessage(STR_PNGMAP_ERR_MISC, STR_BMPMAP_ERROR, 0, 0);
+			fclose(f);
+			BmpDestroyData(&data);
+			return false;
+		}
+
+		ReadHeightmapBMPImageData(*map, &info, &data);
+
+	}
+
+	BmpDestroyData(&data);
+
+	*x = info.width;
+	*y = info.height;
+
+	fclose(f);
+	return true;
+}
+
+static void GrayscaleToMapHeights(uint img_width, uint img_height, byte *map)
+{
+	/* Defines the detail of the aspect ratio (to avoid doubles) */
+	const uint num_div = 16384;
+
+	uint width, height;
+	uint row, col;
+	uint row_pad = 0, col_pad = 0;
+	uint img_scale;
+	uint img_row, img_col;
+	TileIndex tile;
+
+	/* Get map size and calculate scale and padding values */
+	switch (_patches.heightmap_rotation) {
+	case HM_COUNTER_CLOCKWISE:
+		width   = MapSizeX();
+		height  = MapSizeY();
+		break;
+	case HM_CLOCKWISE:
+		width   = MapSizeY();
+		height  = MapSizeX();
+		break;
+	default:
+		NOT_REACHED();
+		/* Avoids compiler warnings */
+		return;
+	}
+
+	if ((img_width * num_div) / img_height > ((width * num_div) / height)) {
+		/* Image is wider than map - center vertically */
+		img_scale = (width * num_div) / img_width;
+		row_pad = (height - ((img_height * img_scale) / num_div)) / 2;
+	} else {
+		/* Image is taller than map - center horizontally */
+		img_scale = (height * num_div) / img_height;
+		col_pad = (width - ((img_width * img_scale) / num_div)) / 2;
+	}
+
+	/* Form the landscape */
+	for (row = 0; row < height - 1; row++) {
+		for (col = 0; col < width - 1; col++) {
+			switch (_patches.heightmap_rotation) {
+			case HM_COUNTER_CLOCKWISE: tile = TileXY(col, row); break;
+			case HM_CLOCKWISE:         tile = TileXY(row, col); break;
+			default:                   NOT_REACHED(); return;
+			}
+
+			/* Check if current tile is within the 1-pixel map edge or padding regions */
+			if ((DistanceFromEdge(tile) <= 1) ||
+					(row < row_pad) || (row >= (img_height + row_pad)) ||
+					(col < col_pad) || (col >= (img_width  + col_pad))) {
+				SetTileHeight(tile, 0);
+			} else {
+				/* Use nearest neighbor resizing to scale map data.
+				 *  We rotate the map 45 degrees (counter)clockwise */
+				img_row = (((row - row_pad) * num_div) / img_scale);
+				switch (_patches.heightmap_rotation) {
+				case HM_COUNTER_CLOCKWISE:
+					img_col = (((width - 1 - col - col_pad) * num_div) / img_scale);
+					break;
+				case HM_CLOCKWISE:
+					img_col = (((col - col_pad) * num_div) / img_scale);
+					break;
+				default:
+					NOT_REACHED();
+					/* Avoids compiler warnings */
+					return;
+				}
+
+				assert(img_row < img_height);
+				assert(img_col < img_width);
+
+				/* Color scales from 0 to 255, OpenTTD height scales from 0 to 15 */
+				SetTileHeight(tile, map[img_row * img_width + img_col] / 16);
+			}
+			MakeClear(tile, CLEAR_GRASS, 3);
+		}
+	}
+}
+
+/**
+ * This function takes care of the fact that land in OpenTTD can never differ
+ * more than 1 in height
+ */
+static void FixSlopes(void)
+{
+	uint width, height;
+	uint row, col;
+	byte current_tile;
+
+	/* Adjust height difference to maximum one horizontal/vertical change. */
+	width   = MapSizeX();
+	height  = MapSizeY();
+
+	/* Top and left edge */
+	for (row = 1; row < height - 2; row++) {
+		for (col = 1; col < width - 2; col++) {
+			/* Find lowest tile; either the top or left one */
+			current_tile = TileHeight(TileXY(col - 1, row)); // top edge
+			if (TileHeight(TileXY(col, row - 1)) < current_tile) {
+				current_tile = TileHeight(TileXY(col, row - 1)); // left edge
+			}
+
+			/* Does the height differ more than one? */
+			if (TileHeight(TileXY(col, row)) >= (uint)current_tile + 2) {
+				/* Then change the height to be no more than one */
+				SetTileHeight(TileXY(col, row), current_tile + 1);
+			}
+		}
+	}
+
+	/* Bottom and right edge */
+	for (row = height - 2; row > 0; row--) {
+		for (col = width - 2; col > 0; col--) {
+			/* Find lowest tile; either the bottom and right one */
+			current_tile = TileHeight(TileXY(col + 1, row)); // bottom edge
+			if (TileHeight(TileXY(col, row + 1)) < current_tile) {
+				current_tile = TileHeight(TileXY(col, row + 1)); // right edge
+			}
+
+			/* Does the height differ more than one? */
+			if (TileHeight(TileXY(col, row)) >= (uint)current_tile + 2) {
+				/* Then change the height to be no more than one */
+				SetTileHeight(TileXY(col, row), current_tile + 1);
+			}
+		}
+	}
+}
+
+/**
+ * Reads the heightmap with the correct file reader
+ */
+static bool ReadHeightMap(char *filename, uint *x, uint *y, byte **map)
+{
+	switch (_file_to_saveload.mode) {
+#ifdef WITH_PNG
+		case SL_PNG:
+			return ReadHeightmapPNG(filename, x, y, map);
+#endif /* WITH_PNG */
+		case SL_BMP:
+			return ReadHeightmapBMP(filename, x, y, map);
+
+		default:
+			NOT_REACHED();
+			/* Avoids compiler warnings */
+			return false;
+	}
+}
+
+bool GetHeightmapDimensions(char *filename, uint *x, uint *y)
+{
+	return ReadHeightMap(filename, x, y, NULL);
+}
+
+void LoadHeightmap(char *filename)
+{
+	uint x, y;
+	byte *map = NULL;
+
+	if (!ReadHeightMap(filename, &x, &y, &map)) {
+		free(map);
+		return;
+	}
+
+	GrayscaleToMapHeights(x, y, map);
+	free(map);
+
+	FixSlopes();
+	MarkWholeScreenDirty();
+}
+
+void FlatEmptyWorld(byte tile_height)
+{
+	uint width, height;
+	uint row, col;
+
+	width  = MapSizeX();
+	height = MapSizeY();
+
+	for (row = 2; row < height - 2; row++) {
+		for (col = 2; col < width - 2; col++) {
+			SetTileHeight(TileXY(col, row), tile_height);
+		}
+	}
+
+	FixSlopes();
+	MarkWholeScreenDirty();
+}