Fix SVG flip when svg.image_noscale is True

Author: dmcdougall

lib/matplotlib/backends/backend_svg.py

@@ -743,9 +743,12 @@ def draw_image(self, gc, x, y, im, dx=None, dy=None, transform=None):
             self.writer.start(u'g', attrib={u'clip-path': u'url(#%s)' % clipid})
 
         trans = [1,0,0,1,0,0]
+        h,w = im.get_size_out()
         if rcParams['svg.image_noscale']:
             trans = list(im.get_matrix())
             trans[5] = -trans[5]
+            trans[3] = -trans[3]
+            y += h
             attrib[u'transform'] = generate_transform([(u'matrix', tuple(trans))])
             assert trans[1] == 0
             assert trans[2] == 0

lib/matplotlib/tests/baseline_images/test_backend_svg/noscale.pdf

@@ -5,6 +5,7 @@
 from io import BytesIO
 import xml.parsers.expat
 from matplotlib.testing.decorators import knownfailureif, cleanup
+from matplotlib.testing.decorators import image_comparison
 
 @cleanup
 def test_visibility():
@@ -30,3 +31,13 @@ def test_visibility():
 
     parser = xml.parsers.expat.ParserCreate()
     parser.Parse(buf) # this will raise ExpatError if the svg is invalid
+
+@image_comparison(baseline_images=['noscale'], remove_text=True)
+def test_noscale():
+    X, Y = np.meshgrid(np.arange(-5, 5, 1), np.arange(-5, 5, 1))
+    Z = np.sin(Y**2)
+
+    fig = plt.figure()
+    ax = fig.add_subplot(1, 1, 1)
+    ax.imshow(Z, cmap='gray')
+    plt.rcParams['svg.image_noscale'] = True