- Update to version 2.8.1:
* Fix imcrop for non-square images, a regression introduced in
version 2.8.0.

- Update to version 2.8.0:
* The following functions are new: hough, imhmax, ntsc2rgb,
imextendedmax, imhmin, rgb2ntsc, imextendedmin, imimposemin,
viscircles, imfindcircles, imsharpen, wiener2.
* Octave version 4.0 is no longer supported. This makes Octave
version 4.2.0 the minimum requirement.
* The functions ntsc2rgb and rgb2ntsc have been removed in Octave
core version 4.4 and are now part of the image package. In a
similar manner, rgb2gray, which has always been part of the image
package, is part of Octave core version 4.4. The versions in
the image package will only be installed if they are missing
from Octave to avoid shadowing the core functions.
* imcrop will now adjust the region to crop to the image
boundaries when the region to crop goes beyond the image
boundaries.
* ycbcr2rgb, rgb2ycbcr, and rgb2gray will return an image of
class single if the input was class single (they were previously
returning a double for such cases).
* The function imdither has been removed. This function hadn't
work since Octave version 3.8.0 and would need to be
rewritten. The function dither from Octave core should be
used instead but hasn't been implemented yet. Instead of
rewriting imdither, the missing dither function should be
written. See bug #41768.
* graythresh will now clip values outside the [0 1] range in
images of floating point class. A side effect of this is that