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Cairo: A Vector Graphics Library | ![]() |
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Top | Description |
cairo_matrix_t; void cairo_matrix_init (cairo_matrix_t *matrix, double xx, double yx, double xy, double yy, double x0, double y0); void cairo_matrix_init_identity (cairo_matrix_t *matrix); void cairo_matrix_init_translate (cairo_matrix_t *matrix, double tx, double ty); void cairo_matrix_init_scale (cairo_matrix_t *matrix, double sx, double sy); void cairo_matrix_init_rotate (cairo_matrix_t *matrix, double radians); void cairo_matrix_translate (cairo_matrix_t *matrix, double tx, double ty); void cairo_matrix_scale (cairo_matrix_t *matrix, double sx, double sy); void cairo_matrix_rotate (cairo_matrix_t *matrix, double radians); cairo_status_t cairo_matrix_invert (cairo_matrix_t *matrix); void cairo_matrix_multiply (cairo_matrix_t *result, const cairo_matrix_t *a, const cairo_matrix_t *b); void cairo_matrix_transform_distance (const cairo_matrix_t *matrix, double *dx, double *dy); void cairo_matrix_transform_point (const cairo_matrix_t *matrix, double *x, double *y);
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()
.
typedef struct { double xx; double yx; double xy; double yy; double x0; double y0; } cairo_matrix_t;
A cairo_matrix_t holds an affine transformation, such as a scale, rotation, shear, or a combination of those. The transformation of a point (x, y) is given by:
x_new = xx * x + xy * y + x0; y_new = yx * x + yy * y + y0;
double |
xx component of the affine transformation |
double |
yx component of the affine transformation |
double |
xy component of the affine transformation |
double |
yy component of the affine transformation |
double |
X translation component of the affine transformation |
double |
Y translation component of the affine transformation |
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;
|
a cairo_matrix_t |
|
xx component of the affine transformation |
|
yx component of the affine transformation |
|
xy component of the affine transformation |
|
yy component of the affine transformation |
|
X translation component of the affine transformation |
|
Y translation component of the affine transformation |
void cairo_matrix_init_identity (cairo_matrix_t *matrix);
Modifies matrix
to be an identity transformation.
|
a cairo_matrix_t |
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.
|
a cairo_matrix_t |
|
amount to translate in the X direction |
|
amount to translate in the Y direction |
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.
|
a cairo_matrix_t |
|
scale factor in the X direction |
|
scale factor in the Y direction |
void cairo_matrix_init_rotate (cairo_matrix_t *matrix, double radians);
Initialized matrix
to a transformation that rotates by radians
.
|
a cairo_matrix_t |
|
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. |
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.
|
a cairo_matrix_t |
|
amount to translate in the X direction |
|
amount to translate in the Y direction |
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.
|
a cairo_matrix_t |
|
scale factor in the X direction |
|
scale factor in the Y direction |
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.
|
a cairo_matrix_t |
|
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_status_t cairo_matrix_invert (cairo_matrix_t *matrix);
Changes matrix
to be the inverse of it's 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.
|
a cairo_matrix_t |
Returns : |
If matrix has an inverse, modifies matrix to
be the inverse matrix and returns CAIRO_STATUS_SUCCESS . Otherwise,
returns CAIRO_STATUS_INVALID_MATRIX .
|
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
.
|
a cairo_matrix_t in which to store the result |
|
a cairo_matrix_t |
|
a cairo_matrix_t |
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
.
|
a cairo_matrix_t |
|
X component of a distance vector. An in/out parameter |
|
Y component of a distance vector. An in/out parameter |
void cairo_matrix_transform_point (const cairo_matrix_t *matrix, double *x, double *y);
Transforms the point (x
, y
) by matrix
.
|
a cairo_matrix_t |
|
X position. An in/out parameter |
|
Y position. An in/out parameter |