Test for new isoline labels skip distance feature

Baseline added in CDAT/uvcdat-testdata#60
Addresses issue#1339

testing/vcs/CMakeLists.txt

@@ -532,6 +532,11 @@ cdat_add_test(vcs_test_taylor_2_quads
       "${cdat_SOURCE_DIR}/testing/vcs/test_isoline_labels.py"
       "${BASELINE_DIR}/test_isoline_labels.png"
       )
+    cdat_add_test(vcs_test_isoline_labelskipdistance
+      "${PYTHON_EXECUTABLE}"
+      "${cdat_SOURCE_DIR}/testing/vcs/test_isoline_labelskipdistance.py"
+      "${BASELINE_DIR}/test_isoline_labelskipdistance.png"
+      )
     cdat_add_test(vcs_test_isofill_isoline_labels
       "${PYTHON_EXECUTABLE}"
       "${cdat_SOURCE_DIR}/testing/vcs/test_isofill_isoline_labels.py"

testing/vcs/test_isoline_labelskipdistance.py

@@ -0,0 +1,46 @@
+import cdms2
+import os
+import sys
+import vcs
+
+baselineImage = sys.argv[1]
+
+pth = os.path.join(os.path.dirname(__file__), "..")
+sys.path.append(pth)
+import checkimage
+
+dataset = cdms2.open(os.path.join(vcs.sample_data, "clt.nc"))
+data = dataset("clt")
+
+canvas = vcs.init()
+canvas.setantialiasing(0)
+canvas.setbgoutputdimensions(1200, 1091, units="pixels")
+canvas.drawlogooff()
+
+isoline = canvas.createisoline()
+isoline.label = "y"
+isoline.labelskipdistance = 15.0
+texts = []
+colors = []
+for i in range(10):
+    text = canvas.createtext()
+    text.color = 20 * i
+    text.height = 12
+    colors.append(255 - text.color)
+    if i % 2 == 0:
+        texts.append(text.name)
+    else:
+        texts.append(text)
+isoline.text = texts
+isoline.linecolors = colors
+
+# Next plot the isolines with labels
+canvas.plot(data, isoline, bg=1)
+
+testImage = os.path.abspath("test_isoline_labelskipdistance.png")
+canvas.png(testImage)
+
+ret = checkimage.check_result_image(testImage, baselineImage,
+                                    checkimage.defaultThreshold)
+
+sys.exit(ret)