diff --git a/slider.py b/slider.py
index 1e91fab..da7d743 100755
--- a/slider.py
+++ b/slider.py
@@ -6,11 +6,16 @@ from pathlib import Path
 from PIL import Image
 from time import time
 from hashlib import sha256
+import click
+from shutil import rmtree
 
 import config
 
 app = Flask(__name__)
 
+cache_resolution = (1920, 1080)
+cache_dir = Path(config.cachedir) / ("%sx%s" % cache_resolution)
+
 
 @app.route("/")
 def random():
@@ -36,24 +41,60 @@ def random_image():
 
 @app.route("/img/<path:filename>")
 def image(filename):
-    cache_resolution = (1920, 1080)
-    cache_dir = Path(config.cachedir) / ("%sx%s" % cache_resolution)
+    cache_filename = create_cache_file(filename)
 
+    return send_from_directory(cache_dir, cache_filename)
+
+
+def rm_cachedir():
+    if Path(config.cachedir).exists():
+        print("Removing cache dir", config.cachedir)
+        rmtree(config.cachedir)
+
+
+def create_cachedir():
     if not cache_dir.exists():
         print("Creating cache dir", cache_dir)
         cache_dir.mkdir(parents=True)
 
-    original_file_path = Path(config.imgdir) / filename
-    cache_file = sha256(str(original_file_path.resolve()).encode("utf-8")).hexdigest()
+
+def create_cache_file(filename):
+    create_cachedir()
+    cache_file = get_cache_filename(filename)
 
     if not (cache_dir / cache_file).exists():
         print("Creating cache file", filename)
-        img = Image.open(original_file_path)
+        img = Image.open(Path(config.imgdir) / filename)
         img.thumbnail(cache_resolution)
         img.save(cache_dir / cache_file, "JPEG")
 
-    return send_from_directory(cache_dir, cache_file)
+    return cache_file
+
+
+def get_cache_filename(filename):
+    original_file_path = Path(config.imgdir) / filename
+    return sha256(str(original_file_path.resolve()).encode("utf-8")).hexdigest()
+
+
+def pre_cache_images():
+    imgdir = Path(config.imgdir)
+    for image_file in sorted(imgdir.glob("*.jpg")):
+        create_cache_file(image_file.relative_to(imgdir))
+
+
+@click.command()
+@click.option("--build-cache", is_flag=True, default=False, help="pre-cache images")
+@click.option(
+    "--clear-cache", is_flag=True, default=False, help="clear cache directory"
+)
+def run_slider(build_cache, clear_cache):
+    if clear_cache:
+        rm_cachedir()
+    if build_cache:
+        pre_cache_images()
+
+    app.run()
 
 
 if __name__ == "__main__":
-    app.run()
+    run_slider()