diff --git a/README.md b/README.md
index 6aaf31e..e822939 100644
--- a/README.md
+++ b/README.md
@@ -18,5 +18,13 @@ bob@stykades:~/work/grassloper$ source ./grassloper.venv/bin/activate
 # this automatically installs the packages that grassloper depends on
 (grassloper.venv) bob@stykades:~/work/grassloper$ pip install -e ./grassloper.git
 # now that grassloper is installed in grassloper.venv and grassloper.venv is activated, simply run it using its command line 'grassloper'
-(grassloper.venv) bob@stykades:~/work/grassloper$ grassloper
+(grassloper.venv) bob@stykades:~/work/grassloper$ grassloper --help
+```
+
+# how to use
+
+`grassloper`'s usage is described with the `--help` command line argument:
+
+```sh
+(grassloper.venv) bob@stykades:~/work/grassloper$ grassloper --help
 ```
diff --git a/grassloper/main.py b/grassloper/main.py
index 3883fa4..9b2a1e9 100755
--- a/grassloper/main.py
+++ b/grassloper/main.py
@@ -6,6 +6,8 @@ import math
 import h5py
 import time
 import scipy.stats
+import argparse
+from improtools.imageprocessing import ImageProcessDebugger, IMovieProcessListener, NullMovieProcessListener, MovieProcessDebugger
 
 
 def create_slope_image(image_width: int, image_height: int, p1_angle: float, p1_radius: float, bg_color: float = 0.0, fg_color: float = 1.0):
@@ -91,8 +93,10 @@ class SlopeFinder():
     def __init__(self, beads_radius: float):
         self.beads_radius = beads_radius
 
-    def find_slope(self, trac_data: TracData, frame_index: int):
+    def find_slope(self, trac_data: TracData, frame_index: int, mo_pro_listener: IMovieProcessListener = NullMovieProcessListener()):
         isbead_image = SlopeFinder.create_isbead_image(trac_data, frame_index, self.beads_radius)
+        mo_pro_listener.onImage(isbead_image, 'isbead')
+        mo_pro_listener.onBaseImage(isbead_image, 'isbead')
         cv2.imwrite('isbead_%04d.tif' % frame_index, isbead_image)
         if False:
             kernel = np.ones((15, 15), np.uint8)
@@ -138,6 +142,11 @@ class SlopeFinder():
         y = [pt[1] for pt in surface_pts]
         lin_regress_result = scipy.stats.linregress(x, y)
         print(lin_regress_result)
+        from_vertex = [0.0, lin_regress_result.intercept]
+        x_max = float(isbead_image.shape[1])
+        to_vertex = [x_max, lin_regress_result.intercept + x_max * lin_regress_result.slope]
+        mo_pro_listener.m_imageProcessListener.onLine( ((from_vertex[0], from_vertex[1]), (to_vertex[0], to_vertex[1])), 'slope')
+
 
     @staticmethod
     def create_isbead_image(trac_data: TracData, frame_index: int, particle_radius: float):
@@ -153,11 +162,23 @@ class SlopeFinder():
 
 
 def main():
+    parser = argparse.ArgumentParser('grassloper', description='estimates the slope of granular surface', epilog='example: \n\tgrassloper --part-pos-file=./grassloper.git/samples/TracTrac/sample002_track.hdf5 --particle-radius=11.0 --debug-dir=\'./improdebug\'')
+    parser.add_argument('--part-pos-file', type=Path, default=None, required=True, help='the input file containing the particle positions')
+    parser.add_argument('--part-pos-file-format', type=str, choices=['tractrac-hdf5'], default='tractrac-hdf5', help='the file format of the input file that contains particle positions')
+    parser.add_argument('--particle-radius', type=float, required=True, help='the radius of the particles in pixels', default=11)
+    parser.add_argument('--debug-dir', type=Path, default=None, help='where to store image processing debug files')
+    args = parser.parse_args()
     # python3 ./tractrac.git/Python/tractrac.py -f ./grassloper.git/samples/sample002.avi --output 1 -a --saveplot
-    trac_data = hdf5_to_trac_data('./grassloper.git/samples/TracTrac/sample002_track.hdf5')
-    slope_finder = SlopeFinder(beads_radius=11.0)
-    for frame_index in range(1, 2):
-        slope_finder.find_slope(trac_data, frame_index=frame_index)
+    if args.debug_dir is not None:
+        mo_pro_listener = MovieProcessDebugger(args.debug_dir)
+    else:
+        mo_pro_listener = NullMovieProcessListener()
+    trac_data = hdf5_to_trac_data(args.part_pos_file)
+    slope_finder = SlopeFinder(beads_radius=args.particle_radius)
+    for frame_index in range(1, 3):
+        mo_pro_listener.onImageProcessingStart()
+        slope_finder.find_slope(trac_data, frame_index=frame_index, mo_pro_listener=mo_pro_listener)
+        mo_pro_listener.onImageProcessingEnd()
 
     # slope_image = create_slope_image(image_width=128, image_height=256, p1_angle=0.7, p1_radius=3.0)
     # cv2.imwrite(str(Path('toto.tif')), slope_image)