fixed and added barrel distortion

extensions/fablabchemnitz_distortion.py

@@ -0,0 +1,99 @@
+import math
+import re
+import inkex
+from inkex import bezier
+from inkex.paths import Path, CubicSuperPath
+
+class DistortionExtension(inkex.Effect):
+    def __init__(self):
+        inkex.Effect.__init__(self)
+        self.arg_parser.add_argument("--lambda_coef", type=float, default=-5.0, help="command line help")
+
+    def distort_coordinates(self, x, y):
+        """Method applies barrel distorsion to given points with distorsion center in center of image, selected to 
+        
+        Args:
+            x (float): X coordinate of given point
+            y (float): Y coordinate of given point
+        
+        Returns:
+            tuple(float, float): Tuple with X,Y distorted coordinates of given point
+        """
+        x_u = (x - self.x_c) / (self.width + self.height)
+        y_u = (y - self.y_c) / (self.width + self.height)
+        x_d = x_u / 2 / (self.q * y_u**2 + x_u**2 * self.q) * (1 - math.sqrt(1 - 4 * self.q * y_u**2 - 4 * x_u**2 * self.q))
+        y_d = y_u / 2 / (self.q * y_u**2 + x_u**2 * self.q) * (1 - math.sqrt(1 - 4 * self.q * y_u**2 - 4 * x_u**2 * self.q))
+        x_d *= self.width + self.height
+        y_d *= self.width + self.height
+        x_d += self.x_c
+        y_d += self.y_c
+        return x_d, y_d
+
+
+
+    def split_into_nodes(self, nodes_number=1000):
+        for id, node in self.svg.selected.items():
+            if node.tag == inkex.addNS('path', 'svg'):
+                p = CubicSuperPath(node.get('d'))
+                new = []
+                for sub in p:
+                    new.append([sub[0][:]])
+                    i = 1
+                    while i <= len(sub) - 1:
+                        length = bezier.cspseglength(
+                            new[-1][-1], sub[i])
+
+                        splits = nodes_number
+                        for s in range(int(splits), 1, -1):
+                            new[-1][-1], next, sub[
+                                i] = bezier.cspbezsplitatlength(
+                                    new[-1][-1], sub[i], 1.0 / s)
+                            new[-1].append(next[:])
+                        new[-1].append(sub[i])
+                        i += 1
+                node.set('d', str(CubicSuperPath(new)))
+
+    def effect(self):
+        if re.match(r'g\d+',
+                    list(self.svg.selected.items())[0][0]) is not None:
+            raise SystemExit(
+                "You are trying to distort group of objects.\n This extension works only with path objects due to Inkscape API restrictions.\n Ungroup your objects and try again."
+            )
+        self.split_into_nodes()
+        self.q = self.options.lambda_coef
+        nodes = []
+        for id, node in self.svg.selected.items():
+            if node.tag == inkex.addNS('path', 'svg'):
+                path = Path(node.get('d')).to_arrays()
+                nodes += path
+        nodes_filtered = [x for x in nodes if x[0] != 'Z']
+        x_coordinates = [x[-1][-2] for x in nodes_filtered]
+        y_coordinates = [y[-1][-1] for y in nodes_filtered]
+        self.width = max(x_coordinates) - min(x_coordinates)
+        self.height = max(y_coordinates) - min(y_coordinates)
+        self.x_c = sum(x_coordinates) / len(x_coordinates)
+        self.y_c = sum(y_coordinates) / len(y_coordinates)
+        for id, node in self.svg.selected.items():
+            if node.tag == inkex.addNS('path', 'svg'):
+                path = Path(node.get('d')).to_arrays()
+                distorted = []
+                first = True
+                for cmd, params in path:
+                    if cmd != 'Z':
+                        if first == True:
+                            x = params[-2]
+                            y = params[-1]
+                            distorted.append(
+                                ['M',
+                                 list(self.distort_coordinates(x, y))])
+                            first = False
+                        else:
+                            x = params[-2]
+                            y = params[-1]
+                            distorted.append(
+                                ['L', self.distort_coordinates(x, y)])
+                node.set('d', str(Path(distorted)))
+
+
+if __name__ == '__main__':
+    DistortionExtension().run()