Added Hologram effect by Benjamin Elder

Author: allo-

filters/__init__.py

@@ -66,3 +66,4 @@ def apply_filters(frame, mask, part_masks, heatmap_masks, image_filters):
 from . import video
 from . import webcam
 from . import anonymize
+from . import hologram

filters/hologram.py

@@ -0,0 +1,45 @@
+import cv2
+import filters
+import numpy as np
+
+# Based on the blog post of Benjamin Elder
+# https://elder.dev/posts/open-source-virtual-background/
+# License: CC-BY 4.0
+
+def shift_image(input_img, dx, dy):
+    img = np.roll(input_img, dy, axis=0)
+    img = np.roll(img, dx, axis=1)
+    if dy>0:
+        img[:dy, :] = 0
+    elif dy<0:
+        img[dy:, :] = 0
+    if dx>0:
+        img[:, :dx] = 0
+    elif dx<0:
+        img[:, dx:] = 0
+    return img
+
+class Hologram:
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def apply(self, *args, **kwargs):
+        frame = kwargs['frame'].astype(np.uint8)
+        frame[:,:,:3] = cv2.applyColorMap(frame[:,:,:3], cv2.COLORMAP_WINTER)
+        frame[:,:,:3] = cv2.cvtColor(frame[:,:,:3], cv2.COLOR_BGR2RGB)
+        # add a halftone effect
+        bandLength, bandGap = 2, 3
+        for y in range(frame.shape[0]):
+            if y % (bandLength+bandGap) < bandLength:
+                frame[y,:,:3] = frame[y,:,:3] * np.random.uniform(0.1, 0.3)
+        # add some ghosting
+        holo_blur = cv2.addWeighted(frame[:,:,:3], 0.2,
+                                    shift_image(frame[:,:,:3], 5, 5), 0.8, 0)
+        holo_blur = cv2.addWeighted(holo_blur, 0.4,
+                                    shift_image(frame[:,:,:3], -5, -5), 0.6, 0)
+        # combine with the original color, oversaturated
+        frame[:,:,:3] = cv2.addWeighted(frame[:,:,:3], 0.5, holo_blur, 0.6, 0)
+        return frame.astype(np.float)
+
+
+filters.register_filter("hologram", Hologram)