init overlay and auto split

src/main/java/stirling/software/SPDF/utils/GeneralUtils.java

@@ -1,6 +1,8 @@
 package stirling.software.SPDF.utils;
 
+import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.nio.file.FileVisitResult;
@@ -12,6 +14,8 @@ import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.springframework.web.multipart.MultipartFile;
+import java.io.FileOutputStream;
 public class GeneralUtils {
 
 	public static void deleteDirectory(Path path) throws IOException {
@@ -48,6 +52,18 @@ public class GeneralUtils {
 	    }
 	}
 
+	public static File multipartToFile(MultipartFile multipart) throws IOException {
+        Path tempFile = Files.createTempFile("overlay-", ".pdf");
+        try (InputStream in = multipart.getInputStream(); 
+             FileOutputStream out = new FileOutputStream(tempFile.toFile())) {
+            byte[] buffer = new byte[1024];
+            int bytesRead;
+            while ((bytesRead = in.read(buffer)) != -1) {
+                out.write(buffer, 0, bytesRead);
+            }
+        }
+        return tempFile.toFile();
+    }
 	
 	public static Long convertSizeToBytes(String sizeStr) {
 	    if (sizeStr == null) {