diff --git a/main.go b/main.go
index a08d899..03b40d0 100644
--- a/main.go
+++ b/main.go
@@ -1,10 +1,12 @@
-// vi:ts=4:sts=4:sw=4:noet:tw=72
+// (c) 2018 Karthik Karanth (https://github.com/medakk/gotiny)
+// (c) 2018-2021 Andreas Neue <an@dnix.de>
 
 package main
 
 import (
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"strconv"
@@ -23,7 +25,7 @@ func init() {
 	flag.Parse()
 }
 
-func resizeHandler(w http.ResponseWriter, r *http.Request) {
+func transform(w http.ResponseWriter, r *http.Request) {
 	// Get the query parameters from the request URL
 	path := r.URL.EscapedPath()
 	parm := strings.Split(path, "/")
@@ -43,81 +45,92 @@ func resizeHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer resp.Body.Close()
+	// Ensure that a valid response was given
+	if resp.StatusCode/100 != 2 {
+		writeError(w, imgPath, method, fmt.Sprintf("failed to fetch image (%v)", resp.StatusCode), http.StatusBadRequest)
+		return
+	}
+
+	buf := []byte{}
+	errMsg := ""
+	errCode := 200
 
 	switch method {
-	case "resize":
-		allowed := strings.Split(*sizesFilter, ",")
-		forbidden := true
-		if allowed[0] == "*" {
-			forbidden = false
-		} else {
-			for _, v := range allowed {
-				if args == v {
-					forbidden = false
-					break
-				}
-			}
-		}
-		if forbidden {
-			writeError(w, imgPath, method, "size is not allowed", http.StatusForbidden)
-			return
-		}
-
-		size := strings.Split(args, "x")
-		if len(size) < 2 {
-			writeError(w, imgPath, method, "url, width, and height are required", http.StatusBadRequest)
-			return
-		}
-		width := size[0]
-		height := size[1]
-
-		// Validate that all three required fields are present
-		if imgPath == "" || width == "" || height == "" {
-			writeError(w, imgPath, method, "url, width, and height are required", http.StatusBadRequest)
-			return
-		}
-
-		// Convert width and height to integers
-		iw, errW := strconv.Atoi(width)
-		ih, errH := strconv.Atoi(height)
-		if errW != nil || errH != nil {
-			writeError(w, imgPath, method, "width and height must be integers", http.StatusBadRequest)
-			return
-		}
-
-		// Ensure that a valid response was given
-		if resp.StatusCode/100 != 2 {
-			writeError(w, imgPath, method, fmt.Sprintf("failed to fetch image (%v)", resp.StatusCode), http.StatusBadRequest)
-			return
-		}
-
-		// Read from response body, convert and write to output buffer
-		img, err := vips.NewImageFromReader(resp.Body)
-		if err != nil {
-			writeError(w, imgPath, method, fmt.Sprintf("%v", err), http.StatusInternalServerError)
-			return
-		}
-		err = img.Thumbnail(iw, ih, 0)
-		if err != nil {
-			writeError(w, imgPath, method, fmt.Sprintf("%v", err), http.StatusInternalServerError)
-			return
-		}
-		ep := vips.NewDefaultExportParams() // default export params are sufficient
-		buf, _, _ := img.Export(ep)
-		_, err = w.Write(buf)
-		if err != nil {
-			writeError(w, imgPath, method, fmt.Sprintf("%v", err), http.StatusInternalServerError)
-			return
-		}
-	
+	case "pass":
+		break
 		
+	case "resize":
+		buf, errMsg, errCode = doResize(resp.Body, args)
+		if buf == nil {
+			writeError(w, imgPath, method, errMsg, errCode)
+		}
+
 	case "thumbnail":
+		break
 
 	default:
 		writeError(w, imgPath, method, "unknown method", http.StatusBadRequest)
 		return
 	}
 
+	_, err = w.Write(buf)
+	if err != nil {
+		writeError(w, imgPath, method, fmt.Sprintf("%v", err), http.StatusInternalServerError)
+		return
+	}
+}
+
+func doResize(body io.ReadCloser, args string) ([]byte, string, int) {
+	allowed := strings.Split(*sizesFilter, ",")
+	forbidden := true
+	if allowed[0] == "*" {
+		forbidden = false
+	} else {
+		for _, v := range allowed {
+			if args == v {
+				forbidden = false
+				break
+			}
+		}
+	}
+	if forbidden {
+		return nil, "size is not allowed", http.StatusForbidden
+	}
+
+	size := strings.Split(args, "x")
+	if len(size) < 2 {
+		return nil, "width and height are required", http.StatusBadRequest
+	}
+	width := size[0]
+	height := size[1]
+
+	// Validate that all three required fields are present
+	if width == "" || height == "" {
+		return nil, "width and height are required", http.StatusBadRequest
+	}
+
+	// Convert width and height to integers
+	iw, errW := strconv.Atoi(width)
+	ih, errH := strconv.Atoi(height)
+	if errW != nil || errH != nil {
+		return nil, "width and height must be integers", http.StatusBadRequest
+	}
+
+	// Read from response body, convert and write to output buffer
+	img, err := vips.NewImageFromReader(body)
+	if err != nil {
+		return nil, fmt.Sprintf("%v", err), http.StatusInternalServerError
+	}
+	err = img.Thumbnail(iw, ih, 0)
+	if err != nil {
+		return nil, fmt.Sprintf("%v", err), http.StatusInternalServerError
+	}
+	ep := vips.NewDefaultExportParams() // default export params are sufficient
+	buf, _, _ := img.Export(ep)
+	if err != nil {
+		return nil, fmt.Sprintf("%v", err), http.StatusInternalServerError
+	}
+	return buf, "", 0
 }
 
 func writeError(w http.ResponseWriter, imgPath, method, err string, status int) {
@@ -130,6 +143,6 @@ func main() {
 	vips.Startup(nil)
 	defer vips.Shutdown()
 
-	http.HandleFunc("/", resizeHandler)
+	http.HandleFunc("/", transform)
 	log.Fatal(http.ListenAndServe(*listenAddr, nil))
 }