Significant changes to the mmand package are laid out below for each release.

===============================================================================

VERSION 1.7.0

- There is now support for libdispatch (aka Grand Central Dispatch) as an
  alternative to OpenMP for parallelisation on supported platforms
  (particularly macOS, but also Linux). The configure script now checks for
  the necessary library and syntax support.
- The distanceTransform() and resample() functions gain a "threads" argument to
  set the number of threads to use (for OpenMP only).
- Use by the included LEMON library of C++ allocator methods deprecated in
  C++17 and removed in C++20 has been patched out for compatibility with
  upcoming R releases.

===============================================================================

VERSION 1.6.3

- The package now avoids using std::iterator, which is deprecated in C++17.

===============================================================================

VERSION 1.6.2

- Too-eager updating of data in-place could lead to errors in some elements of
  a multidimensional distance transform. This has been corrected. (Reported by
  Fabio Boschetti.)

===============================================================================

VERSION 1.6.1

- display() tests are now run from the R temporary directory, to avoid
  cluttering up the package directory.
- Distance transform tests are now skipped on Solaris, due to irreproducible
  failures on CRAN.

===============================================================================

VERSION 1.6.0

- A separable distance transform is now available through the new
  distanceTransform() function. This maps the distances from each array element
  to the nearest boundary between foreground and background, and can be useful
  for estimating the width of image features. (Hat-tip to Chris Rorden and
  Philip Rideout.)
- It is now possible to suppress the creation of a new device by display(), by
  setting the "mmand.display.newDevice" option to FALSE.
- Tests have been migrated from the "testthat" framework to "tinytest", and
  coverage has been improved.

===============================================================================

VERSION 1.5.4

- The range attribute is now properly updated when an image is binarised within
  the threshold() function. (Reported by @GhostValk, issue #5.)
- Compile-time tweaks to meet updated CRAN requirements.

===============================================================================

VERSION 1.5.3

- A configure script is now used to check for OpenMP support on non-Windows
  platforms. This can be helpful in certain build environments on macOS.

===============================================================================

VERSION 1.5.2

- Resampling with the box kernel should no longer produce an erroneous
  "chequered" pattern. (Reported by Steffen Ehrmann, issue #3.)

===============================================================================

VERSION 1.5.1

- The connected components algorithm will no longer erroneously wrap around
  image boundaries. (Reported by Steffen Ehrmann, issue #2.)

===============================================================================

VERSION 1.5.0

- The five-lobe Lanczos windowed sinc kernel function is now available through
  the lanczosKernel() function, and may be used for resampling.
- The new sketch() function can be used to show a compact ASCII representation
  of a 2D greyscale image or other matrix.
- Experimental support for image skeletonisation has been added through the
  skeletonise() function and its alias, skeletonize(). Three different
  algorithms are available, with different limitations. Please see the README
  or ?skeletonise for details.
- Logical data is now accepted by package functions, in addition to integer
  and double-valued data.
- The display() function now handles 2D objects of class "array", and respects
  image attributes set by the "loder" package.
- The morph() function gains a renormalise option, and some new operators.
- Infinite, NaN and NA values are now ignored by threshold() when using the
  k-means method (since kmeans() itself does not handle them gracefully).
  Elements with any of these values are replaced with NAs in the result.
- The binary() function now returns the unique value in an attribute, if
  applicable.
- The binarise() function may now also be spelled binarize().
- A new binary test image, of an upper-case B, has been added.
- The "loder" package is now used instead of "png" for reading PNG images.
- The package no longer depends on "reportr".

===============================================================================

VERSION 1.4.1

- A buffer overflow picked up by valgrind has been corrected.

===============================================================================

VERSION 1.4.0

- The C++ back-end for resample() has been rewritten to improve speed and fix
  implementation issues with cubic spline interpolation. This function (only)
  will now also be parallelised using OpenMP, if your compiler supports it.
- Dilation now works properly with asymmetric kernels. (Reported by
  Marcin Skowronek.)
- The package no longer depends on RcppEigen.

===============================================================================

VERSION 1.3.0

- The package can now find connected components in images, representing
  contiguous subregions, using the new components() function. The LEMON network
  library is used to solve the associated graph problem.
- The Sobel-Feldman kernel and filter are now available through new functions.
  These can be used to obtain a finite-difference gradient.
- The new symmetric() function reports whether or not an array is symmetric.
- Gaussian smoothing in multiple dimensions has been made much faster by
  exploiting the separability of the kernel. Sigma values of zero may also be
  used in some dimensions. (Hat-tip to Tim Tierney.)
- Erosion and dilation did not work as documented when the kernel had a zero at
  its centre. This has been corrected. (Reported by Scott Flanagan.)
- Zero-sum kernels are now properly handled.

===============================================================================

VERSION 1.2.0

- A function has been added for thresholding arrays, either using a literal
  threshold value, or implicitly using k-means clustering.
- The display() function now supports multichannel images (e.g., RGB, RGBA).
  Zero values are also now set to NA when adding to an existing image, to make
  those pixels transparent.

===============================================================================

VERSION 1.1.0

- The README.md file has been expanded into a full tutorial for the package,
  complete with visual examples.
- Calls to the morph() function with merge="sum" previously failed to adjust
  final pixel values when the whole kernel was not used, notably at the edges
  of images. This led to values lower than expected. The bug has now been
  corrected.
- The test image has been replaced by a less traditional, but also less sexist,
  alternative.
- Package tests have been updated to make use of new functionality in version
  0.9 of the "testthat" package.

===============================================================================

VERSION 1.0.0

- The back-end code for the package has been completely rewritten, using C++
  and Rcpp rather than C.
- The package can now perform image resampling, via resample(). This requires a
  different type of kernel but is conceptually related to the existing
  functions based on morph().
- The morph() function has been generalised to allow for various new
  operations. In the process, the concepts of "brush" and "eraser" kernels have
  been removed.
- 2D arrays (i.e. matrices or 2D images) can now be visualised using the new
  display() function.
- Functions for mean and median filtering have been added.
- There are additional functions for establishing whether an array is binary,
  and for obtaining information about the structure of a neighbourhood within
  an array.
- Kernels now have a plot() method.
- The classical image processing test image, "lena", has been added to the
  package.
- A suite of tests has been added.

===============================================================================

VERSION 0.1.2

- Brush kernels which include NAs, notably diamond-shaped kernels, are now
  properly handled by the C code. The value of the output array was sometimes
  overwritten by that of the input array when it should not have been.
  
===============================================================================

VERSION 0.1.1

- A mistake in internal memory management which could lead to a segmentation
  fault has been corrected.

===============================================================================

VERSION 0.1.0

- First public release.

===============================================================================
