diff --git a/README.md b/README.md
index 75f6f80..f489f44 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ The difference between this plugin and the lektor [thumbnail](https://www.getlek
  TL;DR: What does this plugin do?
 ---------------------------------
 + It will generate ``JPEG`` images in the sizes you configured of all images in your Lektor content.
-+ It try to optimize the images with the [guetzli](https://github.com/google/guetzli) JPEG encoder. *(You have to install the guetzli binary by yourself)*
++ It can optionally optimize the images with the [guetzli](https://github.com/google/guetzli) JPEG encoder. *(You have to install the guetzli binary by yourself)*
 
  Usage
 -------
@@ -29,7 +29,7 @@ To install the plugin, just add ``lektor-image-resize`` to your plugins from the
 lektor plugins add lektor-image-resize
 ```
 
-You **have to install** the [guetzli](https://github.com/google/guetzli) JPEG encoder.
+If you want to use the [guetzli](https://github.com/google/guetzli) JPEG encoder for image post-processing, you have to install it manually.
 ```bash
 # example
 apt install guetzli
@@ -54,6 +54,7 @@ max_height = 800
 
 [woowee]
 max_width = 2000
+use_guetzli = True
 ```
 
 Will take a file called `waffle.jpg` and create the files `waffle-small.jpg`,
@@ -61,5 +62,8 @@ Will take a file called `waffle.jpg` and create the files `waffle-small.jpg`,
 of whether the original file is smaller, so you can link without worrying
 whether a file will exist or not. If the original file is smaller than the width
 you have specified, the file will only be copied, and will not be resized.
+
+If you want to run guetzli at the generated output, set ``use_guetzli`` to ``True``.
+
 The `max_width`/`max_height` parameters work like for the [Lektor
 thumbnail](https://www.getlektor.com/docs/api/db/record/thumbnail/) command.
diff --git a/lektor_image_resize.py b/lektor_image_resize.py
index 928fd4d..5e87cbe 100644
--- a/lektor_image_resize.py
+++ b/lektor_image_resize.py
@@ -22,12 +22,14 @@ def process_image(
     height=None,
     mode=None,
     quality=None,
+    use_guetzli=False,
     extra_params=None,
 ):
     """Build image from source image, optionally compressing and resizing.
     "source_image" is the absolute path of the source in the content directory,
     "dst_filename" is the absolute path of the target in the output directory.
     """
+    reporter.report_debug_info("processing image:", dst_filename)
     if width is None and height is None:
         raise ValueError("Must specify at least one of width or height.")
 
@@ -56,8 +58,9 @@ def process_image(
 
     reporter.report_debug_info("imagemagick cmd line", cmdline)
     portable_popen(cmdline).wait()
-    reporter.report_debug_info("guetzli cmd line", cmd2line)
-    portable_popen(cmd2line).wait()
+    if use_guetzli:
+        reporter.report_debug_info("guetzli cmd line", cmd2line)
+        portable_popen(cmd2line).wait()
 
 @buildprogram(Image)
 class ResizedImageBuildProgram(AttachmentBuildProgram):
@@ -85,14 +88,16 @@ def build_artifact(self, artifact):
             if not height:
                 _, height = compute_dimensions(width, None, w, h)
 
+            use_guetzli = bool(conf.get("use_guetzli", "0"))
+
+            if not use_guetzli:
+                use_guetzli = False
+
             df = artifact.source_obj.url_path
             ext_pos = df.rfind(".")
-            if df[ext_pos + 1 :] == 'svg':
-                dst_filename = "%s-%s.png" % (df[:ext_pos], item)
-            else:
-                dst_filename = "%s-%s.%s" % (df[:ext_pos], item, df[ext_pos + 1 :])
+            dst_filename = "%s-%s.%s" % (df[:ext_pos], item, df[ext_pos + 1 :])
 
-            def closure(dst_filename, source_img, width, height, resize_image=True):
+            def closure(dst_filename, source_img, width, height, resize_image=True, ):
                 # We need this closure, otherwise variables get updated and this
                 # doesn't work at all.
                 @ctx.sub_artifact(artifact_name=dst_filename, sources=[source_img])
@@ -107,7 +112,8 @@ def build_thumbnail_artifact(artifact):
                             artifact.dst_filename,
                             width,
                             height,
-                            quality=85,
+                            quality=89,
+                            use_guetzli=use_guetzli,
                             extra_params=[
                                 "-strip",
                                 "-interlace",