Kwimage

Added
* kwimage.morphology
* kwimage.draw_header_text
* `Mask.to_multi_polygon` and `Polygon.to_mask` now take a flag `pixels_are`
which will treat pixels as areas or points.


Fixed
* But in imresize when a dim was automatically computed to be zero.

Changed
* Using `math` is much faster than `numpy` for scalars, switching to that in kwimage.Affine
* Added default behavior to `draw_text_on_image` when origin is unspecified.
* Polygon and MultiPolygon coerce work better with geojson
* Work on new robust normalizers (see `normalize_intensity`)

Added
* Add function `gaussian_blur`
* Added `pad` as an argument to `stack_images` to override a negative `overlap`
* Added gaussian sigma kernel heuristic
* Added interleave as an option to COG write
* Add `fill` to `PolygonList`

Fixed
* Polygons now better respect the color parameter in detections draw on
* kwimage.imread can now take pathlib.Path objects
* Fixed issue with warp of empty keypoints

Changed
* Changed default GDAL compression in `kwimage.imwrite` from RAW to DEFLATE
* Better overview support in `kwimage.imwrite`
* Improved speed of several `kwimage.Affine` routines.

Added
* Wrapped `itk.imread` with `kwimage.imread`.
* Added `kwimage.imcrop`
* Add `large_warp_dim` to `kwimage.warp_affine`

Fixed
* `kwimage.warp_affine` now returns a sensible result when the source or
destination image has no size.
* `kwimage.grab_test_image` now checks sha256 instead of sha1.
* Fixed tests that downloaded data, but did not check hashes

Changed
* Improved `cv2.imread` auto-space default based on the available backend.
Should no longer need to specify it unless working with cv2.

Fixed
* C-Extension errors for boxes now fallback on pure-python

Added
* Enhanced capabilities of `draw_text_on_image`
* `Mask.draw_on` will now draw on an empty image if none is provided

Fixed
* C-Extension errors for masks now fallback on pure-python
* Not having `imgaug` no longer warns
* Fixed issues with generic warps

Added

* added `border_mode` and `border_value` to `warp_affine`.

* The `img` arg in `draw_text_on_image` can now be specified as a dictionary
for control over canvas generation.


Fixed

* issue computing canvas size in `draw_text_on_image` when an image is not given.

* failing to have imgaug no longer crashes arbitrary functions in annotation warp methods.