Transformations: Cairo: A Vector Graphics Library

+ + +

Transformations

Transformations — Manipulating the current transformation matrix

Functions

++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

+void +	+cairo_translate () +
+void +	+cairo_scale () +
+void +	+cairo_rotate () +
+void +	+cairo_transform () +
+void +	+cairo_set_matrix () +
+void +	+cairo_get_matrix () +
+void +	+cairo_identity_matrix () +
+void +	+cairo_user_to_device () +
+void +	+cairo_user_to_device_distance () +
+void +	+cairo_device_to_user () +
+void +	+cairo_device_to_user_distance () +

Description

The current transformation matrix, ctm, is a +two-dimensional affine transformation that maps all coordinates and other +drawing instruments from the user space into the +surface's canonical coordinate system, also known as the device +space.

Functions

cairo_translate ()

void
+cairo_translate (cairo_t *cr,
+                 double tx,
+                 double ty);

Modifies the current transformation matrix (CTM) by translating the +user-space origin by (tx +, ty +). This offset is interpreted as a +user-space coordinate according to the CTM in place before the new +call to cairo_translate(). In other words, the translation of the +user-space origin takes place after any existing transformation.

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo context
tx	amount to translate in the X direction
ty	amount to translate in the Y direction

Since: 1.0

cairo_scale ()

void
+cairo_scale (cairo_t *cr,
+             double sx,
+             double sy);

Modifies the current transformation matrix (CTM) by scaling the X +and Y user-space axes by sx + and sy + respectively. The scaling of +the axes takes place after any existing transformation of user +space.

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo context
sx	scale factor for the X dimension
sy	scale factor for the Y dimension

Since: 1.0

cairo_rotate ()

void
+cairo_rotate (cairo_t *cr,
+              double angle);

Modifies the current transformation matrix (CTM) by rotating the +user-space axes by angle + radians. The rotation of the axes takes +places after any existing transformation of user space. The +rotation direction for positive angles is from the positive X axis +toward the positive Y axis.

Parameters

+++++ + + + + + + + + + + + + +

cr	a cairo context
angle	angle (in radians) by which the user-space axes will be +rotated

Since: 1.0

cairo_transform ()

void
+cairo_transform (cairo_t *cr,
+                 const cairo_matrix_t *matrix);

Modifies the current transformation matrix (CTM) by applying +matrix + as an additional transformation. The new transformation of +user space takes place after any existing transformation.

Parameters

+++++ + + + + + + + + + + + + +

cr	a cairo context
matrix	a transformation to be applied to the user-space axes

Since: 1.0

cairo_set_matrix ()

void
+cairo_set_matrix (cairo_t *cr,
+                  const cairo_matrix_t *matrix);

Modifies the current transformation matrix (CTM) by setting it +equal to matrix +.

Parameters

+++++ + + + + + + + + + + + + +

cr	a cairo context
matrix	a transformation matrix from user space to device space

Since: 1.0

cairo_get_matrix ()

void
+cairo_get_matrix (cairo_t *cr,
+                  cairo_matrix_t *matrix);

Stores the current transformation matrix (CTM) into matrix +.

Parameters

+++++ + + + + + + + + + + + + +

cr	a cairo context
matrix	return value for the matrix

Since: 1.0

cairo_identity_matrix ()

void
+cairo_identity_matrix (cairo_t *cr);

Resets the current transformation matrix (CTM) by setting it equal +to the identity matrix. That is, the user-space and device-space +axes will be aligned and one user-space unit will transform to one +device-space unit.

Parameters

+++++ + + + + + +

a cairo context

Since: 1.0

cairo_user_to_device ()

void
+cairo_user_to_device (cairo_t *cr,
+                      double *x,
+                      double *y);

Transform a coordinate from user space to device space by +multiplying the given point by the current transformation matrix +(CTM).

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo context
x	X value of coordinate (in/out parameter)
y	Y value of coordinate (in/out parameter)

Since: 1.0

cairo_user_to_device_distance ()

void
+cairo_user_to_device_distance (cairo_t *cr,
+                               double *dx,
+                               double *dy);

Transform a distance vector from user space to device space. This +function is similar to cairo_user_to_device() except that the +translation components of the CTM will be ignored when transforming +(dx +,dy +).

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo context
dx	X component of a distance vector (in/out parameter)
dy	Y component of a distance vector (in/out parameter)

Since: 1.0

cairo_device_to_user ()

void
+cairo_device_to_user (cairo_t *cr,
+                      double *x,
+                      double *y);

Transform a coordinate from device space to user space by +multiplying the given point by the inverse of the current +transformation matrix (CTM).

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo
x	X value of coordinate (in/out parameter)
y	Y value of coordinate (in/out parameter)

Since: 1.0

cairo_device_to_user_distance ()

void
+cairo_device_to_user_distance (cairo_t *cr,
+                               double *dx,
+                               double *dy);

Transform a distance vector from device space to user space. This +function is similar to cairo_device_to_user() except that the +translation components of the inverse CTM will be ignored when +transforming (dx +,dy +).

Parameters

+++++ + + + + + + + + + + + + + + + + + +

cr	a cairo context
dx	X component of a distance vector (in/out parameter)
dy	Y component of a distance vector (in/out parameter)

Since: 1.0