Description
cairo_matrix_t is used throughout cairo to convert between different
coordinate spaces. A cairo_matrix_t 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 cairo_t, represented as a
cairo_matrix_t, defines the transformation from user-space
coordinates to device-space coordinates. See cairo_get_matrix() and
cairo_set_matrix().
Functions
cairo_matrix_init ()
void
cairo_matrix_init (cairo_matrix_t *matrix,
double xx,
double yx,
double xy,
double yy,
double x0,
double y0);
Sets matrix
to be the affine transformation given by
xx
, yx
, xy
, yy
, x0
, y0
. The transformation is given
by:
x_new = xx * x + xy * y + x0;
y_new = yx * x + yy * y + y0;
Since: 1.0
cairo_matrix_init_identity ()
void
cairo_matrix_init_identity (cairo_matrix_t *matrix);
Modifies matrix
to be an identity transformation.
Since: 1.0
cairo_matrix_init_translate ()
void
cairo_matrix_init_translate (cairo_matrix_t *matrix,
double tx,
double ty);
Initializes matrix
to a transformation that translates by tx
and
ty
in the X and Y dimensions, respectively.
Since: 1.0
cairo_matrix_init_scale ()
void
cairo_matrix_init_scale (cairo_matrix_t *matrix,
double sx,
double sy);
Initializes matrix
to a transformation that scales by sx
and sy
in the X and Y dimensions, respectively.
Since: 1.0
cairo_matrix_init_rotate ()
void
cairo_matrix_init_rotate (cairo_matrix_t *matrix,
double radians);
Initialized matrix
to a transformation that rotates by radians
.
Since: 1.0
cairo_matrix_translate ()
void
cairo_matrix_translate (cairo_matrix_t *matrix,
double tx,
double ty);
Applies a translation by tx
, ty
to the transformation in
matrix
. The effect of the new transformation is to first translate
the coordinates by tx
and ty
, then apply the original transformation
to the coordinates.
Since: 1.0
cairo_matrix_scale ()
void
cairo_matrix_scale (cairo_matrix_t *matrix,
double sx,
double sy);
Applies scaling by sx
, sy
to the transformation in matrix
. The
effect of the new transformation is to first scale the coordinates
by sx
and sy
, then apply the original transformation to the coordinates.
Since: 1.0
cairo_matrix_rotate ()
void
cairo_matrix_rotate (cairo_matrix_t *matrix,
double radians);
Applies rotation by radians
to the transformation in
matrix
. The effect of the new transformation is to first rotate the
coordinates by radians
, then apply the original transformation
to the coordinates.
Since: 1.0
cairo_matrix_invert ()
cairo_status_t
cairo_matrix_invert (cairo_matrix_t *matrix);
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.
Since: 1.0
cairo_matrix_multiply ()
void
cairo_matrix_multiply (cairo_matrix_t *result,
const cairo_matrix_t *a,
const cairo_matrix_t *b);
Multiplies the affine transformations in a
and b
together
and stores the result in result
. The effect of the resulting
transformation is to first apply the transformation in a
to the
coordinates and then apply the transformation in b
to the
coordinates.
It is allowable for result
to be identical to either a
or b
.
Since: 1.0
cairo_matrix_transform_distance ()
void
cairo_matrix_transform_distance (const cairo_matrix_t *matrix,
double *dx,
double *dy);
Transforms the distance vector (dx
,dy
) by matrix
. This is
similar to cairo_matrix_transform_point() except that the translation
components of the transformation are ignored. The calculation of
the returned vector is as follows:
dx2 = dx1 * a + dy1 * c;
dy2 = dx1 * b + dy1 * d;
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
.
Since: 1.0
cairo_matrix_transform_point ()
void
cairo_matrix_transform_point (const cairo_matrix_t *matrix,
double *x,
double *y);
Transforms the point (x
, y
) by matrix
.
Since: 1.0