/usr/lib/python3/dist-packages/cairocffi/matrix.py is in python3-cairocffi 0.8.0-0ubuntu2.
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"""
cairocffi.matrix
~~~~~~~~~~~~~~~~
Transformation matrices.
:copyright: Copyright 2013 by Simon Sapin
:license: BSD, see LICENSE for details.
"""
from . import ffi, cairo, _check_status
class Matrix(object):
"""A 2D transformation matrix.
Matrices are used throughout cairo to convert between
different coordinate spaces.
A :class:`Matrix` holds an affine transformation,
such as a scale, rotation, shear, or a combination of these.
The transformation of a point (x,y) is given by::
x_new = xx * x + xy * y + x0
y_new = yx * x + yy * y + y0
The current transformation matrix of a :class:`Context`,
represented as a :class:`Matrix`,
defines the transformation from user-space coordinates
to device-space coordinates.
See :meth:`Context.get_matrix` and :meth:`Context.set_matrix`.
The default values produce an identity matrix.
Matrices can be compared with ``m1 == m2`` and ``m2 != m2``
as well as multiplied with ``m3 = m1 * m2``.
"""
def __init__(self, xx=1, yx=0, xy=0, yy=1, x0=0, y0=0):
self._pointer = ffi.new('cairo_matrix_t *')
cairo.cairo_matrix_init(self._pointer, xx, yx, xy, yy, x0, y0)
@classmethod
def init_rotate(cls, radians):
"""Return a new :class:`Matrix` for a transformation
that rotates by :obj:`radians`.
:type radians: float
:param radians:
Angle of rotation, in radians.
The direction of rotation is defined such that
positive angles rotate in the direction
from the positive X axis toward the positive Y axis.
With the default axis orientation of cairo,
positive angles rotate in a clockwise direction.
"""
result = cls()
cairo.cairo_matrix_init_rotate(result._pointer, radians)
return result
def as_tuple(self):
"""Return all of the matrix’s components.
:returns: A ``(xx, yx, xy, yy, x0, y0)`` tuple of floats.
"""
ptr = self._pointer
return (ptr.xx, ptr.yx, ptr.xy, ptr.yy, ptr.x0, ptr.y0)
def copy(self):
"""Return a new copy of this matrix."""
return type(self)(*self.as_tuple())
def __getitem__(self, index):
return getattr(
self._pointer, ('xx', 'yx', 'xy', 'yy', 'x0', 'y0')[index])
def __iter__(self):
return iter(self.as_tuple())
def __eq__(self, other):
return self.as_tuple() == other.as_tuple()
def __ne__(self, other):
return self.as_tuple() != other.as_tuple()
def __repr__(self):
class_ = type(self)
return '%s(%g, %g, %g, %g, %g, %g)' % (
(class_.__name__,) + self.as_tuple())
def multiply(self, other):
"""Multiply with another matrix
and return the result as a new :class:`Matrix` object.
Same as ``self * other``.
"""
res = Matrix()
cairo.cairo_matrix_multiply(
res._pointer, self._pointer, other._pointer)
return res
__mul__ = multiply
def translate(self, tx, ty):
"""Applies a translation by :obj:`tx`, :obj:`ty`
to the transformation in this matrix.
The effect of the new transformation is to
first translate the coordinates by :obj:`tx` and :obj:`ty`,
then apply the original transformation to the coordinates.
.. note::
This changes the matrix in-place.
:param tx: Amount to translate in the X direction.
:param ty: Amount to translate in the Y direction.
:type tx: float
:type ty: float
"""
cairo.cairo_matrix_translate(self._pointer, tx, ty)
def scale(self, sx, sy=None):
"""Applies scaling by :obj:`sx`, :obj:`sy`
to the transformation in this matrix.
The effect of the new transformation is to
first scale the coordinates by :obj:`sx` and :obj:`sy`,
then apply the original transformation to the coordinates.
If :obj:`sy` is omitted, it is the same as :obj:`sx`
so that scaling preserves aspect ratios.
.. note::
This changes the matrix in-place.
:param sx: Scale factor in the X direction.
:param sy: Scale factor in the Y direction.
:type sx: float
:type sy: float
"""
if sy is None:
sy = sx
cairo.cairo_matrix_scale(self._pointer, sx, sy)
def rotate(self, radians):
"""Applies a rotation by :obj:`radians`
to the transformation in this matrix.
The effect of the new transformation is to
first rotate the coordinates by :obj:`radians`,
then apply the original transformation to the coordinates.
.. note::
This changes the matrix in-place.
:type radians: float
:param radians:
Angle of rotation, in radians.
The direction of rotation is defined such that positive angles
rotate in the direction from the positive X axis
toward the positive Y axis.
With the default axis orientation of cairo,
positive angles rotate in a clockwise direction.
"""
cairo.cairo_matrix_rotate(self._pointer, radians)
def invert(self):
"""Changes matrix to be the inverse of its original value.
Not all transformation matrices have inverses;
if the matrix collapses points together (it is degenerate),
then it has no inverse and this function will fail.
.. note::
This changes the matrix in-place.
:raises: :exc:`CairoError` on degenerate matrices.
"""
_check_status(cairo.cairo_matrix_invert(self._pointer))
def inverted(self):
"""Return the inverse of this matrix. See :meth:`invert`.
:raises: :exc:`CairoError` on degenerate matrices.
:returns: A new :class:`Matrix` object.
"""
matrix = self.copy()
matrix.invert()
return matrix
def transform_point(self, x, y):
"""Transforms the point ``(x, y)`` by this matrix.
:param x: X position.
:param y: Y position.
:type x: float
:type y: float
:returns: A ``(new_x, new_y)`` tuple of floats.
"""
xy = ffi.new('double[2]', [x, y])
cairo.cairo_matrix_transform_point(self._pointer, xy + 0, xy + 1)
return tuple(xy)
def transform_distance(self, dx, dy):
"""Transforms the distance vector ``(dx, dy)`` by this matrix.
This is similar to :meth:`transform_point`
except that the translation components of the transformation
are ignored.
The calculation of the returned vector is as follows::
dx2 = dx1 * xx + dy1 * xy
dy2 = dx1 * yx + dy1 * yy
Affine transformations are position invariant,
so the same vector always transforms to the same vector.
If ``(x1, y1)`` transforms to ``(x2, y2)``
then ``(x1 + dx1, y1 + dy1)`` will transform
to ``(x1 + dx2, y1 + dy2)`` for all values of ``x1`` and ``x2``.
:param dx: X component of a distance vector.
:param dy: Y component of a distance vector.
:type dx: float
:type dy: float
:returns: A ``(new_dx, new_dy)`` tuple of floats.
"""
xy = ffi.new('double[2]', [dx, dy])
cairo.cairo_matrix_transform_distance(self._pointer, xy + 0, xy + 1)
return tuple(xy)
def _component_property(name):
return property(
lambda self: getattr(self._pointer, name),
lambda self, value: setattr(self._pointer, name, value),
doc='Read-write attribute access to a single float component.')
xx = _component_property('xx')
yx = _component_property('yx')
xy = _component_property('xy')
yy = _component_property('yy')
x0 = _component_property('x0')
y0 = _component_property('y0')
del _component_property
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