Add makeRampImage

Add lsst.afw.image.testUtils.makeRampImage and a unit test

python/lsst/afw/image/testUtils.py

@@ -26,6 +26,7 @@
 import numpy as np
 
 import lsst.utils.tests
+from .imageLib import ImageF
 from .basicUtils import makeMaskedImageFromArrays
 
 # the asserts are automatically imported so unit tests can find them without special imports;
@@ -47,6 +48,25 @@ def makeGaussianNoiseMaskedImage(dimensions, sigma, variance=1.0):
 
     return makeMaskedImageFromArrays(image, mask, variance)
 
+def makeRampImage(bbox, start=0, stop=None, imageClass=ImageF):
+        """!Make an image whose values are a linear ramp
+
+        @param[in] bbox  bounding box of image (an lsst.afw.geom.Box2I)
+        @param[in] start  starting ramp value, inclusive
+        @param[in] stop  ending ramp value, inclusive; if None, increase by integer values
+        @param[in] imageClass  type of image (e.g. lsst.afw.image.ImageF)
+        """
+        im = imageClass(bbox)
+        imDim = im.getDimensions()
+        numPix = imDim[0]*imDim[1]
+        imArr = im.getArray()
+        if stop is None:
+            # increase by integer values
+            stop = start + numPix - 1
+        rampArr = np.linspace(start=start, stop=stop, endpoint=True, num=numPix, dtype=imArr.dtype)
+        imArr[:] = np.reshape(rampArr, (imDim[1], imDim[0])) # numpy arrays are transposed w.r.t. afwImage
+        return im
+
 @lsst.utils.tests.inTestCase
 def assertImagesNearlyEqual(testCase, image0, image1, skipMask=None,
         rtol=1.0e-05, atol=1e-08, msg="Images differ"):

tests/testImageTestUtils.py

@@ -0,0 +1,62 @@
+import unittest
+
+import numpy as np
+
+import lsst.utils.tests
+import lsst.afw.geom as afwGeom
+import lsst.afw.image as afwImage
+from lsst.afw.image.testUtils import makeRampImage
+
+class MakeRampImageTestCase(lsst.utils.tests.TestCase):
+    """!Unit tests for makeRampImage"""
+    def testUnitInterval(self):
+        """!Test small ramp images with unit interval for known values
+        """
+        for imageClass in (afwImage.ImageU, afwImage.ImageF, afwImage.ImageD):
+            dim = afwGeom.Extent2I(7, 9)
+            box = afwGeom.Box2I(afwGeom.Point2I(-1, 3), dim)
+            numPix = dim[0]*dim[1]
+            for start in (-5, 0, 4):
+                if imageClass == afwImage.ImageU and start < 0:
+                    continue
+                predStop = start + numPix - 1  # for integer steps
+                for stop in (None, predStop):
+                    rampImage = makeRampImage(bbox=box, start=start, stop=predStop, imageClass=imageClass)
+                    predArr = np.arange(start, predStop+1)
+                    self.assertEqual(len(predArr), numPix)
+                    predArr.shape = (dim[1], dim[0])
+                    self.assertImagesNearlyEqual(rampImage, predArr)
+
+    def testNonUnitIntervals(self):
+        """!Test a small ramp image with non-integer increments
+        """
+        for imageClass in (afwImage.ImageU, afwImage.ImageF, afwImage.ImageD):
+            dim = afwGeom.Extent2I(7, 9)
+            box = afwGeom.Box2I(afwGeom.Point2I(-1, 3), dim)
+            numPix = dim[0]*dim[1]
+            for start in (-5.1, 0, 4.3):
+                if imageClass == afwImage.ImageU and start < 0:
+                    continue
+                for stop in (7, 1001.5, 5.4):
+                    rampImage = makeRampImage(bbox=box, start=start, stop=stop, imageClass=imageClass)
+                    dtype = rampImage.getArray().dtype
+                    predArr = np.linspace(start, stop, num=numPix, endpoint=True, dtype=dtype)
+                    predArr.shape = (dim[1], dim[0])
+                    self.assertImagesNearlyEqual(rampImage, predArr)
+
+
+def suite():
+    """!Returns a suite containing all the test cases in this module."""
+    lsst.utils.tests.init()
+
+    suites = []
+    suites += unittest.makeSuite(MakeRampImageTestCase)
+    suites += unittest.makeSuite(lsst.utils.tests.MemoryTestCase)
+    return unittest.TestSuite(suites)
+
+def run(exit=False):
+    """!Run the tests"""
+    lsst.utils.tests.run(suite(), exit)
+
+if __name__ == "__main__":
+    run(True)