Add bezier interpolation to colormap_class.

- Add a new example to demo.f90.

example/demo.f90

@@ -21,15 +21,16 @@
 ! SOFTWARE.
 !-------------------------------------------------------------------------------
 ! Contributed by vmagnin: 2023-09-26
-! Last modification: vmagnin 2023-10-19
+! Last modification: gha3mi 2024-01-28
 !-------------------------------------------------------------------------------
 
 program demo
- use forcolormap, only: Colormap, colormaps_list, wp
+ use forcolormap, only: Colormap, colormaps_list, wp, bezier
  implicit none
 
  integer :: i
  type(Colormap) :: cmap, custom_cmap
+ integer, allocatable :: colors(:,:)
  ! A discrete colormap with 8 levels, from black to white:
  integer, dimension(0:7, 3) :: my_colormap = reshape( [ &
  0, 0, 0, &
@@ -68,6 +69,16 @@ program demo
  call test_colormap(custom_cmap, 'a_loaded_colormap_test', encoding='binary')
  call custom_cmap%print()
 
+ ! You can also create your own colormap using bezier interpolation:
+ ! Define control colors.
+ allocate(colors(3,3))
+ colors(1,:) = [255, 0, 0] ! Red
+ colors(2,:) = [0, 255, 0] ! Green
+ colors(3,:) = [0, 0, 255] ! Blue
+ call custom_cmap%create('custom_bezier', 0.0_wp, 2.0_wp, bezier(colors, levels=1024)) ! levels is optional, default is 256
+ call custom_cmap%colorbar('custom_colorbar_bezier', encoding='binary')
+ call test_colormap(custom_cmap, 'custom_test_bezier', encoding='binary') 
+
  contains
 
  subroutine test_colormap(self, filename, encoding)

src/colormap_class.f90

@@ -21,7 +21,7 @@
 ! SOFTWARE.
 !-------------------------------------------------------------------------------
 ! Contributed by vmagnin: 2023-09-26
-! Last modification: gha3mi 2024-01-06
+! Last modification: gha3mi 2024-01-28
 !-------------------------------------------------------------------------------
 
 
@@ -34,7 +34,7 @@ module forcolormap
  implicit none
  private
 
- public :: wp
+ public :: wp, bezier
 
  ! List of built-in colormaps:
  character(*), dimension(*), public, parameter :: colormaps_list = &
@@ -927,4 +927,44 @@ pure subroutine extract(self, extractedLevels, name, zmin, zmax, reverse)
  end if
  end subroutine extract
 
+ ! Create colormap from continuous Bezier interpolation of control colors
+ pure function bezier(colors, levels) result(map)
+ integer, dimension(:,:), intent(in) :: colors
+ integer, intent(in), optional :: levels
+ integer, dimension(:,:), allocatable :: map
+ real(wp), dimension(:,:), allocatable :: map_r
+ integer :: order, i, j, levels_
+ real(wp) :: t
+
+ ! Set default value for levels
+ if (present(levels)) then
+ levels_ = levels
+ else
+ levels_ = 256
+ end if
+
+ ! Order of the Bezier curve
+ order = size(colors, 1) - 1
+
+ allocate(map_r(levels_,3), map(levels_,3)) ! 3 for RGB
+ do i = 1,levels_
+ t = real(i-1, wp) / real(levels_-1, wp)
+ map_r(i,:) = 0.0_wp
+ do j = 0, order
+ map_r(i,:) = map_r(i,:) + real(colors(j+1,:), wp)*&
+ real(factorial(order), wp)/(real(factorial(j), wp)*real(factorial(order-j), wp)) * t**j * (1.0_wp-t)**(order-j)
+ end do
+ map(i,:) = scale_real_int(map_r(i,:), 0, 255) ! Scale to integer RGB range
+ end do
+ end function bezier
+
+ ! Factorial function used for Bezier interpolation
+ pure function factorial(n) result(result)
+ integer, intent(in) :: n
+ integer :: result, i
+ result = 1
+ do concurrent (i = 2:n)
+ result = result * i
+ end do
+ end function factorial
 end module forcolormap