warp-coords

warp_coords

skimage.transform.warp_coords(coord_map, shape, dtype=) [source]

Build the source coordinates for the output of a 2-D image warp.

Parameters:	coord_map : callable like GeometricTransform.inverse Return input coordinates for given output coordinates. Coordinates are in the shape (P, 2), where P is the number of coordinates and each element is a (row, col) pair. shape : tuple Shape of output image (rows, cols[, bands]). dtype : np.dtype or string dtype for return value (sane choices: float32 or float64).
Returns:	coords : (ndim, rows, cols[, bands]) array of dtype dtype Coordinates for scipy.ndimage.map_coordinates, that will yield an image of shape (orows, ocols, bands) by drawing from source points according to the coord_transform_fn.

Notes

This is a lower-level routine that produces the source coordinates for 2-D images used by warp().

It is provided separately from warp to give additional flexibility to users who would like, for example, to re-use a particular coordinate mapping, to use specific dtypes at various points along the the image-warping process, or to implement different post-processing logic than warp performs after the call to ndi.map_coordinates.

Examples

Produce a coordinate map that shifts an image up and to the right:

>>> from skimage import data
>>> from scipy.ndimage import map_coordinates
>>>
>>> def shift_up10_left20(xy):
...     return xy - np.array([-20, 10])[None, :]
>>>
>>> image = data.astronaut().astype(np.float32)
>>> coords = warp_coords(shift_up10_left20, image.shape)
>>> warped_image = map_coordinates(image, coords)