diff options
Diffstat (limited to 'fg21sim/utils/grid.py')
| -rw-r--r-- | fg21sim/utils/grid.py | 38 |
1 files changed, 29 insertions, 9 deletions
diff --git a/fg21sim/utils/grid.py b/fg21sim/utils/grid.py index cc99407..9bc1ec8 100644 --- a/fg21sim/utils/grid.py +++ b/fg21sim/utils/grid.py @@ -8,6 +8,7 @@ Grid utilities. import numpy as np from scipy import ndimage +import healpy as hp from .draw import ellipse @@ -97,7 +98,7 @@ def make_grid_ellipse(center, size, resolution, rotation=None): The array with elements representing the latitudes of each grid pixel. Also, the latitudes are fixed to be in the valid range [-90, 90]. - grid : 2D float `~numpy.ndarray` + gridmap : 2D float `~numpy.ndarray` The array containing the specified ellipse, where the pixels corresponding to the ellipse with positive values, while other pixels are zeros. @@ -118,12 +119,13 @@ def make_grid_ellipse(center, size, resolution, rotation=None): r0, c0 = np.floor(np.array(shape) / 2.0).astype(np.int) r_radius, c_radius = np.ceil(0.5*np.array(size)/resolution).astype(np.int) rr, cc = ellipse(r0, c0, r_radius, c_radius, shape=shape) - grid = np.zeros(shape) - grid[rr, cc] = 1.0 + gridmap = np.zeros(shape) + gridmap[rr, cc] = 1.0 if rotation is not None: # Rotate the ellipse - grid = ndimage.rotate(grid, angle=rotation, order=1, reshape=False) - return (lon, lat, grid) + gridmap = ndimage.rotate(gridmap, angle=rotation, order=1, + reshape=False) + return (lon, lat, gridmap) def map_grid_to_healpix(grid, nside): @@ -141,17 +143,35 @@ def map_grid_to_healpix(grid, nside): Returns ------- - hpmap : 1D `~numpy.ndarray` - Mapped HEALPix map in *RING* ordering. + indexes : 1D `~numpy.ndarray` + The indexes of the effective HEALPix pixels that are mapped from + the input coordinate grid. The indexes are in RING ordering. + values : 1D `~numpy.ndarray` + The values of each output HEALPix pixels with respect the above + indexes. NOTE ---- Generally, the input coordinate grid has higher resolution than the - output HEALPix map, so down-sampling is performed. + output HEALPix map, so down-sampling is performed by averaging the + pixels that map to the same HEALPix pixel. However, note that the total flux is *NOT PRESERVED* for the mapping (or reprojection) procedure. XXX/TODO: - Implement the flux-preserving algorithm (reference ???) """ - raise NotImplementedError("TODO") + lon, lat, gridmap = grid + phi = np.radians(lon) + theta = np.radians(90.0 - lat) + ipix = hp.ang2pix(nside, theta, phi, nest=False) + # Get the corresponding input grid pixels for each HEALPix pixel + indexes, counts = np.unique(ipix, return_counts=True) + shape = (len(indexes), max(counts)) + datamap = np.zeros(shape) * np.nan + # TODO: how to avoid this explicit loop ?? + for i, idx in enumerate(indexes): + pixels = gridmap[ipix == idx] + datamap[i, :len(pixels)] = pixels + values = np.nanmean(datamap, axis=1) + return (indexes, values) |