Added some camera geometry functionality for camera team

In particular, mappings between amp/ccd/focal plane coordinates
using an LsstCameraTransforms object, but also getAmpImage and
channelToAmp free functions

policy/cameraHeader.yaml

@@ -170,7 +170,7 @@ CCD_E2V : &CCD_E2V
 
 CCD_ITL : &CCD_ITL
     detectorType : 0
-    refpos : [2036.5, 2000.5]
+    refpos : [2035.5, 1999.5]
     offset : [.nan, .nan]
     # This is the orientation we need to put the serial direction along the x-axis
     bbox : [[0, 0], [4071, 3999]]

python/lsst/obs/lsst/cameraTransforms.py

@@ -366,24 +366,18 @@ def ampPixelToCcdPixel(x, y, detector, channel):
     """
 
     amp = channelToAmp(detector, channel)
-    rawBBox, rawDataBBox = amp.getRawBBox(), amp.getRawDataBBox()
+    bbox = amp.getRawDataBBox()
+
     # Allow for flips (due e.g. to physical location of the amplifiers)
-    w, h = rawBBox.getDimensions()
+    x, y = geom.PointI(x, y)            # definitely ints
+    w, h = bbox.getDimensions()
     if amp.getRawFlipX():
-        rawBBox.flipLR(w)
-        rawDataBBox.flipLR(w)
-
-        x = rawBBox.getWidth() - x - 1
+        x = w - x - 1
 
     if amp.getRawFlipY():
-        rawBBox.flipTB(h)
-        rawDataBBox.flipTB(h)
-
-        y = rawBBox.getHeight() - y - 1
-
-    dxy = rawBBox.getBegin() - rawDataBBox.getBegin()   # correction for overscan etc.
+        y = h - y - 1
 
-    return amp.getBBox().getBegin() + dxy + geom.ExtentI(x, y)
+    return amp.getBBox().getBegin() + geom.ExtentI(x, y)
 
 
 def ccdPixelToAmpPixel(xy, detector):
@@ -411,31 +405,28 @@ def ccdPixelToAmpPixel(xy, detector):
     RuntimeError
         If the requested pixel doesn't lie on the detector
     """
+    xy = geom.PointI(xy)                # use pixel coordinates
 
     found = False
     for amp in detector:
-        if geom.BoxD(amp.getBBox()).contains(xy):
+        if amp.getBBox().contains(xy):
+            x, y = xy - amp.getBBox().getBegin()  # coordinates within data segment
             found = True
-            xy = geom.PointI(xy)     # pixel coordinates as ints
             break
 
     if not found:
         raise RuntimeError("Point (%g, %g) does not lie on detector %s" % (xy[0], xy[1], detector.getName()))
 
-    x, y = xy - amp.getBBox().getBegin()   # offset from origin of amp's data segment
-
     # Allow for flips (due e.g. to physical location of the amplifiers)
-    w, h = amp.getRawDataBBox().getDimensions()
+    w, h = amp.getBBox().getDimensions()
+
     if amp.getRawFlipX():
         x = w - x - 1
 
     if amp.getRawFlipY():
         y = h - y - 1
 
-    dxy = amp.getRawBBox().getBegin() - amp.getRawDataBBox().getBegin()   # correction for overscan etc.
-    xy = geom.ExtentI(x, y) - dxy
-
-    return amp, xy
+    return amp, geom.PointI(x, y)
 
 
 def focalMmToCcdPixel(camera, focalPlaneXY):

tests/test_lsstCam.py

@@ -24,8 +24,9 @@
 import unittest
 
 import lsst.utils.tests
-from lsst.geom import arcseconds, Extent2I
+from lsst.geom import arcseconds, Extent2I, PointD, PointI
 import lsst.afw.image
+from lsst.obs.lsst.cameraTransforms import LsstCameraTransforms
 
 from lsst.obs.lsst.testHelper import ObsLsstButlerTests, ObsLsstObsBaseOverrides
 
@@ -162,6 +163,62 @@ def testDetectorName(self):
         with self.assertRaises(RuntimeError):
             self.mapper._extractDetectorName({'visit': 1})
 
+    def testCameraTransforms(self):
+        """Test the geometry routines requested by the camera team
+
+        These are found in cameraTransforms.py"""
+
+        camera = self.butler.get('camera', immediate=True)
+
+        raft = 'R22'
+        sensor = 'S11'
+        ccdid = f"{raft}_{sensor}"
+
+        lct = LsstCameraTransforms(camera)
+
+        # check that we can map ccd pixels to amp pixels
+        for cxy, apTrue in [
+                ((0,   0), (1, 508, 0)),  # noqa: E241
+                ((509, 0), (2, 508, 0)),
+        ]:
+            ap = lct.ccdPixelToAmpPixel(*cxy, ccdid)
+            self.assertEqual(ap, apTrue)
+
+        # check inverse mapping
+        for ap, cpTrue in [
+                ((508, 0, 1), (0, 0)),
+                ((0, 0, 9), (4071, 3999)),
+        ]:
+            cp = lct.ampPixelToCcdPixel(*ap, ccdid)
+            self.assertEqual(cp, PointI(*cpTrue))
+
+        # check round-tripping
+        ampX, ampY, channel = 2, 0, 1
+        cx, cy = lct.ampPixelToCcdPixel(ampX, ampY, channel, ccdid)
+        finalChannel, finalAmpX, finalAmpY = lct.ccdPixelToAmpPixel(cx, cy, ccdid)
+        self.assertEqual((finalAmpX, finalAmpY, finalChannel), (ampX, ampY, channel))
+
+        # Check that four amp pixels near the camera's centre are
+        # indeed close in focal plane coords
+        for ap, fpTrue in [
+                ((508, 1999,   5), ( 0.005, -0.005)),  # noqa: E201,E241
+                ((0,   1999,   4), (-0.005, -0.005)),  # noqa: E201,E241
+                ((0,   1999,  13), (-0.005,  0.005)),  # noqa: E201,E241
+                ((508, 1999,  12), ( 0.005,  0.005)),  # noqa: E201,E241
+        ]:
+            fp = lct.ampPixelToFocalMm(*ap, ccdid)
+            self.assertAlmostEqual((fp - PointD(*fpTrue)).computeNorm(), 0.0)
+
+        # and for ccd coordinates:
+        for cp, fpTrue in [
+                ((2035, 1999), (-0.005, -0.005)),  # noqa: E201,E241
+                ((2036, 1999), ( 0.005, -0.005)),  # noqa: E201,E241
+                ((2035, 2000), (-0.005,  0.005)),  # noqa: E201,E241
+                ((2036, 2000), ( 0.005,  0.005)),  # noqa: E201,E241
+        ]:
+            fp = lct.ccdPixelToFocalMm(*cp, ccdid)
+            self.assertAlmostEqual((fp - PointD(*fpTrue)).computeNorm(), 0.0)
+
 
 class MemoryTester(lsst.utils.tests.MemoryTestCase):
     pass