Fix crash if zooming out near frame edge (alievk#319)

Added clamping of offsets so that lrud always lies within image
boundaries. The adjusted offsets are returned to main so that it is no
longer necessary to test if an offset increase/decrease should be
allowed.

Author: JohanAR

afy/cam_fomm.py

@@ -275,8 +275,8 @@ def select_camera(config):
             frame = frame[..., ::-1]
             frame_orig = frame.copy()
 
-            frame, lrudwh = crop(frame, p=frame_proportion, offset_x=frame_offset_x, offset_y=frame_offset_y)
-            frame_lrudwh = lrudwh
+            frame, (frame_offset_x, frame_offset_y) = crop(frame, p=frame_proportion, offset_x=frame_offset_x, offset_y=frame_offset_y)
+
             frame = resize(frame, (IMG_SIZE, IMG_SIZE))[..., :3]
 
             if find_keyframe:
@@ -323,29 +323,21 @@ def select_camera(config):
                 frame_proportion += 0.05
                 frame_proportion = min(frame_proportion, 1.0)
             elif key == ord('H'):
-                if frame_lrudwh[0] - 1 > 0:
-                    frame_offset_x -= 1
+                frame_offset_x -= 1
             elif key == ord('h'):
-                if frame_lrudwh[0] - 5 > 0:
-                    frame_offset_x -= 5
+                frame_offset_x -= 5
             elif key == ord('K'):
-                if frame_lrudwh[1] + 1 < frame_lrudwh[4]:
-                    frame_offset_x += 1
+                frame_offset_x += 1
             elif key == ord('k'):
-                if frame_lrudwh[1] + 5 < frame_lrudwh[4]:
-                    frame_offset_x += 5
+                frame_offset_x += 5
             elif key == ord('J'):
-                if frame_lrudwh[2] - 1 > 0:
-                    frame_offset_y -= 1
+                frame_offset_y -= 1
             elif key == ord('j'):
-                if frame_lrudwh[2] - 5 > 0:
-                    frame_offset_y -= 5
+                frame_offset_y -= 5
             elif key == ord('U'):
-                if frame_lrudwh[3] + 1 < frame_lrudwh[5]:
-                    frame_offset_y += 1
+                frame_offset_y += 1
             elif key == ord('u'):
-                if frame_lrudwh[3] + 5 < frame_lrudwh[5]:
-                    frame_offset_y += 5
+                frame_offset_y += 5
             elif key == ord('Z'):
                 frame_offset_x = 0
                 frame_offset_y = 0

afy/utils.py

@@ -114,19 +114,27 @@ def __repr__(self):
         return self.__str__()
 
 
+def clamp(value, min_value, max_value):
+    return max(min(value, max_value), min_value)
+
+
 def crop(img, p=0.7, offset_x=0, offset_y=0):
     h, w = img.shape[:2]
     x = int(min(w, h) * p)
     l = (w - x) // 2
     r = w - l
     u = (h - x) // 2
     d = h - u
+
+    offset_x = clamp(offset_x, -l, w - r)
+    offset_y = clamp(offset_y, -u, h - d)
+
     l += offset_x
     r += offset_x
     u += offset_y
     d += offset_y
 
-    return img[u:d, l:r], (l,r,u,d,w,h)
+    return img[u:d, l:r], (offset_x, offset_y)
 
 
 def pad_img(img, target_size, default_pad=0):