lsst.afw.cameraGeom._rotateBBoxBy90 Namespace Reference

Functions
	rotateBBoxBy90 (bbox, n90, dimensions)

Function Documentation

rotateBBoxBy90()

lsst.afw.cameraGeom._rotateBBoxBy90.rotateBBoxBy90	(		bbox,
			n90,
			dimensions )

Rotate a bounding box by an integer multiple of 90 degrees.

Parameters
----------
bbox : `lsst.geom.Box2I`
    Bounding box to rotate.
n90 : `int`
    Number of quarter rotations to perform
dimensions : `tuple` of `int`
    Dimensions of the parent grid.

Returns
-------
newBbox : `lsst.geom.Box`
    Rotated bounding box.

Notes
-----
**TODO:**
    document dimensions better; what does it specify?

Definition at line 29 of file _rotateBBoxBy90.py.

def rotateBBoxBy90(bbox, n90, dimensions):
    """Rotate a bounding box by an integer multiple of 90 degrees.
 
    Parameters
    ----------
    bbox : `lsst.geom.Box2I`
        Bounding box to rotate.
    n90 : `int`
        Number of quarter rotations to perform
    dimensions : `tuple` of `int`
        Dimensions of the parent grid.
 
    Returns
    -------
    newBbox : `lsst.geom.Box`
        Rotated bounding box.
 
    Notes
    -----
    **TODO:**
        document dimensions better; what does it specify?
    """
    while n90 < 0:
        n90 += 4
    n90 %= 4
 
    # sin/cos of the rotation angle
    s = 0
    c = 0
    if n90 == 0:
        s = 0
        c = 1
    elif n90 == 1:
        s = 1
        c = 0
    elif n90 == 2:
        s = 0
        c = -1
    elif n90 == 3:
        s = -1
        c = 0
    else:
        raise ValueError("n90 must be an integer")
 
    centerPixel = lsst.geom.Point2I(int(dimensions[0]/2), int(dimensions[1]/2))
 
    xCorner = numpy.array([(corner.getX() - centerPixel[0])
                           for corner in bbox.getCorners()])
    yCorner = numpy.array([(corner.getY() - centerPixel[1])
                           for corner in bbox.getCorners()])
    x0 = int((c*xCorner - s*yCorner).min())
    y0 = int((s*xCorner + c*yCorner).min())
    x1 = int((c*xCorner - s*yCorner).max())
    y1 = int((s*xCorner + c*yCorner).max())
 
    # Fiddle things a little if the detector has an even number of pixels so that square BBoxes
    # will map into themselves
 
    if n90 == 1:
        if dimensions[0]%2 == 0:
            x0 -= 1
            x1 -= 1
    elif n90 == 2:
        if dimensions[0]%2 == 0:
            x0 -= 1
            x1 -= 1
        if dimensions[1]%2 == 0:
            y0 -= 1
            y1 -= 1
    elif n90 == 3:
        if dimensions[1]%2 == 0:
            y0 -= 1
            y1 -= 1
 
    LLC = lsst.geom.Point2I(centerPixel[0] + x0, centerPixel[1] + y0)
    URC = lsst.geom.Point2I(centerPixel[0] + x1, centerPixel[1] + y1)
 
    newBbox = lsst.geom.Box2I(LLC, URC)
 
    dxy0 = centerPixel[0] - centerPixel[1]
    if n90%2 == 1 and not dxy0 == 0:
        newBbox.shift(lsst.geom.Extent2I(-dxy0, dxy0))
 
    return newBbox