lsst.afw.cameraGeom.rotateBBoxBy90 Namespace Reference

Functions
def	rotateBBoxBy90
	Rotate a bounding box by an integer multiple of 90 degrees. More...

Variables
list	__all__ = ["rotateBBoxBy90"]

Function Documentation

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

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

Todo:

document dimensions better; what does it specify?

Parameters

bbox	bbox to rotate
n90	number of quarter rotations to perform
dimensions	dimensions of the parent grid

Returns

rotated bounding box

Definition at line 28 of file rotateBBoxBy90.py.

def rotateBBoxBy90(bbox, n90, dimensions):
    """!Rotate a bounding box by an integer multiple of 90 degrees

    @todo document dimensions better; what does it specify?

    @param bbox  bbox to rotate
    @param n90  number of quarter rotations to perform
    @param dimensions  dimensions of the parent grid
    @return rotated bounding box
    """
    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 = afwGeom.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 = afwGeom.Point2I(centerPixel[0] + x0, centerPixel[1] + y0)
    URC = afwGeom.Point2I(centerPixel[0] + x1, centerPixel[1] + y1)
 
    newBbox = afwGeom.Box2I(LLC, URC)
        
    dxy0 = centerPixel[0] - centerPixel[1]
    if n90%2 == 1 and not dxy0 == 0:
        newBbox.shift(afwGeom.Extent2I(-dxy0, dxy0))
        
    return newBbox

Variable Documentation

list lsst.afw.cameraGeom.rotateBBoxBy90.__all__ = ["rotateBBoxBy90"]

Definition at line 26 of file rotateBBoxBy90.py.