add bitmap screenshot saving

src/gfx.h

@@ -30,7 +30,7 @@ typedef struct {
 	short y;			// 0x06
 	short width;		// 0x08
 	short height;		// 0x0A
-	short pitch;		// 0x0C
+	short pitch;		// 0x0C			note: this is actually (pitch - width)
 	char pad_0E;		// 0x0E
 	char var_0F;		// 0x0F
 } rct_drawpixelinfo;

src/screenshot.c

@@ -18,7 +18,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *****************************************************************************/
 
+#include <windows.h>
 #include "addresses.h"
+#include "gfx.h"
 #include "rct2.h"
 #include "screenshot.h"
 #include "strings.h"
@@ -48,13 +50,143 @@ void screenshot_check()
 	}
 }
 
+static int screenshot_get_next_path(char *path)
+{
+	char *placeHolder;
+
+	strcpy(path, RCT2_ADDRESS(RCT2_ADDRESS_APP_PATH_SLASH, char));
+	placeHolder = path + strlen(path);
+
+	int i;
+	for (i = 1; i < 1000; i++) {
+		RCT2_GLOBAL(0x013CE952, uint16) = i;
+		format_string(placeHolder, STR_SCR_BMP, 0x013CE952);
+
+		if (GetFileAttributes(path) == INVALID_FILE_ATTRIBUTES && GetLastError() == ERROR_FILE_NOT_FOUND)
+			return i;
+	}
+
+	return -1;
+}
+
+// Bitmap header structs, for cross platform purposes
+typedef struct {
+	uint16 bfType;
+	uint32 bfSize;
+	uint16 bfReserved1;
+	uint16 bfReserved2;
+	uint32 bfOffBits;
+} BitmapFileHeader;
+
+typedef struct {
+	uint32 biSize;
+	sint32 biWidth;
+	sint32 biHeight;
+	uint16 biPlanes;
+	uint16 biBitCount;
+	uint32 biCompression;
+	uint32 biSizeImage;
+	sint32 biXPelsPerMeter;
+	sint32 biYPelsPerMeter;
+	uint32 biClrUsed;
+	uint32 biClrImportant;
+} BitmapInfoHeader;
+
 /**
  * 
  *  rct2: 0x00683D20
  */
 int screenshot_dump()
 {
-	int eax, ebx, ecx, edx, esi, edi, ebp;
-	RCT2_CALLFUNC_X(0x00683D20, &eax, &ebx, &ecx, &edx, &esi, &edi, &ebp);
-	return eax & 0xFFFF;
+	BitmapFileHeader header;
+	BitmapInfoHeader info;
+
+	int i, x, y, index, width, height, stride;
+	char *buffer, path[MAX_PATH], *row, *dst;
+	HFILE hFile;
+	DWORD bytesWritten;
+
+	// Get a free screenshot path
+	if ((index = screenshot_get_next_path(path)) == -1)
+		return -1;
+
+	// Open file for writing
+	hFile = CreateFile(path, GENERIC_WRITE, NULL, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+	if (hFile == INVALID_HANDLE_VALUE)
+		return -1;
+
+	// Allocate buffer
+	buffer = malloc(0xFFFF);
+	if (buffer == NULL) {
+		CloseHandle(hFile);
+		return -1;
+	}
+
+	// Get image size
+	width = RCT2_GLOBAL(RCT2_ADDRESS_SCREEN_WIDTH, uint16);
+	height = RCT2_GLOBAL(RCT2_ADDRESS_SCREEN_HEIGHT, uint16);
+	stride = (width + 3) & 0xFFFFFFFC;
+
+	// File header
+	memset(&header, 0, sizeof(header));
+	header.bfType = 0x4D42;
+	header.bfSize = height * stride + 1038;
+	header.bfOffBits = 1038;
+
+	WriteFile(hFile, &header, sizeof(header), &bytesWritten, NULL);
+	if (bytesWritten != sizeof(header)) {
+		CloseHandle(hFile);
+		free(buffer);
+	}
+
+	// Info header
+	memset(&info, 0, sizeof(info));
+	info.biSize = sizeof(info);
+	info.biWidth = width;
+	info.biHeight = height;
+	info.biPlanes = 1;
+	info.biBitCount = 8;
+	info.biXPelsPerMeter = 2520;
+	info.biYPelsPerMeter = 2520;
+	info.biClrUsed = 246;
+
+	WriteFile(hFile, &info, sizeof(info), &bytesWritten, NULL);
+	if (bytesWritten != sizeof(info)) {
+		CloseHandle(hFile);
+		free(buffer);
+	}
+
+	// Palette
+	memset(buffer, 0, 246 * 4);
+	for (i = 0; i < 246; i++) {
+		buffer[i * 4 + 0] = RCT2_ADDRESS(0x01424680, uint8)[i * 4 + 0];
+		buffer[i * 4 + 1] = RCT2_ADDRESS(0x01424680, uint8)[i * 4 + 1];
+		buffer[i * 4 + 2] = RCT2_ADDRESS(0x01424680, uint8)[i * 4 + 2];
+	}
+
+	WriteFile(hFile, buffer, 246 * 4, &bytesWritten, NULL);
+	if (bytesWritten != 246 * 4) {
+		CloseHandle(hFile);
+		free(buffer);
+	}
+
+	// Image, save upside down
+	rct_drawpixelinfo *dpi = RCT2_ADDRESS(RCT2_ADDRESS_SCREEN_DPI, rct_drawpixelinfo);
+	for (y = dpi->height - 1; y >= 0; y--) {
+		row = dpi->bits + y * (dpi->width + dpi->pitch);
+
+		memset(buffer, 0, stride);
+		memcpy(buffer, row, dpi->width);
+
+		WriteFile(hFile, buffer, stride, &bytesWritten, NULL);
+		if (bytesWritten != stride) {
+			CloseHandle(hFile);
+			free(buffer);
+		}
+	}
+
+	CloseHandle(hFile);
+	free(buffer);
+
+	return index;
 }