npix_circ_exact

npix_circ_exact(x, y, r, *, shape, mask=None, validate=True)

Return exact circular-aperture effective in-frame pixel counts.

Parameters

x, y : scalar or array_like

Aperture center coordinates in pixel units. Shapes must match after numpy.atleast_1d. The return shape matches that broadcast-free input shape, so scalar inputs return one-element arrays.

r : float

Aperture radius in pixels.

shape : tuple[int, int]

Image shape as (ny, nx) used to clip the aperture footprint.

mask : array_like of bool, optional = None

Boolean image mask with shape shape. True pixels are excluded from the returned effective pixel count.

Returns

npix : ndarray

Effective pixel count inside the image frame.

Notes

exact mode uses fractional pixel overlap weights for the analytic aperture footprint.