virtual-image: Do print enroll and verification using transformed images

We used to enroll and verify always the same prints, which made
generating the very same enrolled prints, that simplifies the libfprint
matching.

To make this a bit more real, let's apply some transformations to the
print images before sending them each time

tests/virtual-image.py

@@ -46,6 +46,27 @@ def load_image(img):
 
     return img
 
+
+def transform_image(surface, dx=0, dy=0, dw=0, dh=0, angle=0):
+    assert dw >= 0 and dh >= 0, "dw/dh must be non-negative"
+
+    w = surface.get_width()
+    h = surface.get_height()
+    result = cairo.ImageSurface(cairo.Format.A8, w, h)
+    cr = cairo.Context(result)
+
+    # Transform around center: translate to center, scale, rotate, then
+    # offset the source so its center aligns with the origin.
+    cr.translate(w / 2 + dx, h / 2 + dy)
+    cr.rotate(angle)
+    cr.scale((w - dw) / w, (h - dh) / h)
+    cr.translate(-w / 2, -h / 2)
+
+    cr.set_source_surface(surface)
+    cr.paint()
+    return result
+
+
 if 'FP_PRINTS_PATH' in os.environ:
     prints_path = os.environ['FP_PRINTS_PATH']
 else:
@@ -126,9 +147,12 @@ class VirtualImage(unittest.TestCase):
         while iterate and ctx.pending():
             ctx.iteration(False)
 
-    def send_image(self, image, iterate=True):
+    def send_image(self, image, iterate=True, dx=0, dy=0, dw=0, dh=0, angle=0):
         img = self.prints[image]
 
+        if dx or dy or dw or dh or angle:
+            img = transform_image(img, dx, dy, dw, dh, angle)
+
         mem = img.get_data()
         mem = mem.tobytes()
         assert len(mem) == img.get_width() * img.get_height()
@@ -223,7 +247,7 @@ class VirtualImage(unittest.TestCase):
 
         # Note: Assumes 5 enroll steps for this device!
         self.wait_for_finger_status(FPrint.FingerStatusFlags.NEEDED)
-        self.send_image(image)
+        self.send_image(image, dx=0, dy=0, dw=0, dh=0, angle=0)
         while self._step < 1:
             ctx.iteration(True)
 
@@ -233,8 +257,8 @@ class VirtualImage(unittest.TestCase):
         self.assertEqual(self.dev.get_finger_status(), FPrint.FingerStatusFlags.NEEDED)
         self.send_finger_report(True)
         self.assertEqual(self.dev.get_finger_status(),
-            FPrint.FingerStatusFlags.NEEDED | FPrint.FingerStatusFlags.PRESENT)
-        self.send_image(image)
+                         FPrint.FingerStatusFlags.NEEDED | FPrint.FingerStatusFlags.PRESENT)
+        self.send_image(image, dx=1, dy=0, dw=0, dh=0, angle=0.017)
         while self._step < 2:
             ctx.iteration(True)
         self.send_finger_report(False)
@@ -242,19 +266,19 @@ class VirtualImage(unittest.TestCase):
         self.assertEqual(self.dev.get_finger_status(), FPrint.FingerStatusFlags.NEEDED)
 
         self.send_finger_automatic(True)
-        self.send_image(image)
+        self.send_image(image, dx=-1, dy=1, dw=2, dh=0, angle=-0.035)
         while self._step < 3:
             ctx.iteration(True)
 
         self.assertEqual(self.dev.get_finger_status(), FPrint.FingerStatusFlags.NEEDED)
 
-        self.send_image(image)
+        self.send_image(image, dx=0, dy=-1, dw=0, dh=2, angle=0.035)
         while self._step < 4:
             ctx.iteration(True)
 
         self.assertEqual(self.dev.get_finger_status(), FPrint.FingerStatusFlags.NEEDED)
 
-        self.send_image(image)
+        self.send_image(image, dx=2, dy=0, dw=1, dh=1, angle=-0.017)
         while self._enrolled is None:
             ctx.iteration(True)
 
@@ -282,7 +306,7 @@ class VirtualImage(unittest.TestCase):
         self._verify_fp = None
         self.dev.verify(fp_whorl, callback=verify_cb)
         self.wait_for_finger_status(FPrint.FingerStatusFlags.NEEDED)
-        self.send_image('whorl')
+        self.send_image('whorl', dx=-2, dy=-1, dw=0, dh=0, angle=0.052)
         while self._verify_match is None:
             ctx.iteration(True)
         assert(self._verify_match)
@@ -306,7 +330,7 @@ class VirtualImage(unittest.TestCase):
         self._verify_fp = None
         self.dev.verify(fp_whorl_tended_arch, callback=verify_cb)
         self.wait_for_finger_status(FPrint.FingerStatusFlags.NEEDED)
-        self.send_image('whorl')
+        self.send_image('whorl', dx=3, dy=0, dw=4, dh=2, angle=-0.052)
         while self._verify_match is None:
             ctx.iteration(True)
         assert(self._verify_match)
@@ -422,7 +446,7 @@ class VirtualImage(unittest.TestCase):
         self._verify_fp = None
         self.dev.verify(fp_whorl_new, callback=verify_cb)
         self.wait_for_finger_status(FPrint.FingerStatusFlags.NEEDED)
-        self.send_image('whorl')
+        self.send_image('whorl', dx=-1, dy=2, dw=0, dh=3, angle=0.017)
         while self._verify_match is None:
             ctx.iteration(True)
         assert(self._verify_match)