resizeImageBL <- function ( imx, width, height )

#*****************************************************************************80
#
## resizeImageBL resizes an image using bilinear interpolation.
#
#  Licensing:
#
#    Copyright 2016 James P. Howard, II
#
#    The computer code and data files on this web page are distributed under
#    https://opensource.org/licenses/BSD-2-Clause, the BSD-2-Clause license.
#
#  Modified:
#
#    01 March 2020
#
#  Author:
#
#    Original R code by James Howard;
#    Modifications by John Burkardt.
#
#  Reference:
#
#    James Howard,
#    Computational Methods for Numerical Analysis with R,
#    CRC Press, 2017,
#    ISBN13: 978-1-4987-2363-3.
#
{
  source ( "/home/burkardt/public_html/r_src/bilinear/bilinear.R" )  

  imx.dim <- dim ( imx )
# layers <- imx.dim[3]
  w.orig <- imx.dim[1]
  h.orig <- imx.dim[2]

  w.scale <- ( w.orig - 1 ) / width
  h.scale <- ( h.orig - 1 ) / height

# bl <- array ( 0, c ( height, width, layers ) )

  bl <- array ( 0, c ( height, width ) )

  zb <- matrix ( 0, 2, 2 )

# for ( l in 1 : layers )
# {
    for ( h in 1 : height )
    {
      y <- floor ( h.scale * h )
      if ( y <= 0 )
      {
        y <- 1
      }
      if ( h.orig <= y )
      {
        y <- h.orig - 1
      }

      yb <- c ( y, y + 1 )
      yl <- h.scale * h

      for ( w in 1 : width )
      {
        x <- floor ( w.scale * w )
        if ( x <= 0 )
        {
          x <- 1
        }
        if ( w.orig <= x )
        {
          x <- w.orig - 1
        }
        xb <- c ( x, x + 1 )
        xl <- w.scale * w

        zb[1,1] <- imx[y,x]
        zb[1,2] <- imx[y,x+1]
        zb[2,1] <- imx[y+1,x]
        zb[2,2] <- imx[y+1,x+1]

        bl[h,w] <- bilinear ( xb, yb, zb, xl, yl )
      }
    }
# }

  return ( bl )
}