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############################################################################
#
# File: xforms.icn
#
# Subject: Procedures to do matrix transformations
#
# Author: Stephen W. Wampler and Ralph E. Griswold
#
# Date: March 25, 2002
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# These procedures produce matrices for affine transformation in two
# dimensions and transform point lists.
#
# A point list is a list of Point() records. See gobject.icn.
#
############################################################################
#
# Links: matrix
#
############################################################################
link matrix
procedure transform(p, M) #: transform point list by matrix
local pl, i
# convert p to a matrix for matrix multiply...
every put((pl := [[]])[1], (!p)|1.0) # the 1.0 makes it homogeneous
# do the conversion...
pl := mult_matrix(pl, M)
# convert list back to a point list...
p := copy(p)
every i := 1 to *p do
p[i] := pl[1][i]
return p
end
procedure transform_points(pl,M) #: transform point list
local xformed
every put(xformed := [], !transform(!pl,M))
return xformed
end
procedure set_scale(x, y) #: matrix for scaling
local M
M := identity_matrix(3,3)
M[1][1] := x
M[2][2] := y
return M
end
procedure set_trans(x, y) #: matrix for translation
local M
M := identity_matrix(3,3)
M[*M][1] := x
M[*M][2] := y
return M
end
procedure set_xshear(x) #: matrix for x shear
local M
M := identity_matrix(3,3)
M[1][2] := x
return M
end
procedure set_yshear(y) #: matrix for y shear
local M
M := identity_matrix(3,3)
M[2][1] := y
return M
end
procedure set_rotate(x) #: matrix for rotation
local M
M := identity_matrix(3,3)
M[1][1] := cos(x)
M[2][2] := M[1][1]
M[1][2] := sin(x)
M[2][1] := -M[1][2]
return M
end
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