]> cairo_matrix_t 3 CAIRO Library cairo_matrix_t Generic matrix operations void cairo_matrix_init () void cairo_matrix_init_identity () void cairo_matrix_init_translate () void cairo_matrix_init_scale () void cairo_matrix_init_rotate () void cairo_matrix_translate () void cairo_matrix_scale () void cairo_matrix_rotate () cairo_status_t cairo_matrix_invert () void cairo_matrix_multiply () void cairo_matrix_transform_distance () void cairo_matrix_transform_point () cairo_matrix_t 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(). 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; matrix a cairo_matrix_t xx xx component of the affine transformation yx yx component of the affine transformation xy xy component of the affine transformation yy yy component of the affine transformation x0 X translation component of the affine transformation y0 Y translation component of the affine transformation Since: 1.0 cairo_matrix_init_identity void cairo_matrix_init_identity (cairo_matrix_t *matrix); Modifies matrix to be an identity transformation. matrix a cairo_matrix_t 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. matrix a cairo_matrix_t tx amount to translate in the X direction ty amount to translate in the Y direction 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. matrix a cairo_matrix_t sx scale factor in the X direction sy scale factor in the Y direction 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 . matrix a cairo_matrix_t 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. 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. matrix a cairo_matrix_t tx amount to translate in the X direction ty amount to translate in the Y direction 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. matrix a cairo_matrix_t sx scale factor in the X direction sy scale factor in the Y direction 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. matrix a cairo_matrix_t 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. 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. matrix a cairo_matrix_t If matrix has an inverse, modifies matrix to be the inverse matrix and returns CAIRO_STATUS_SUCCESS. Otherwise, returns CAIRO_STATUS_INVALID_MATRIX. 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 . result a cairo_matrix_t in which to store the result a a cairo_matrix_t b a cairo_matrix_t 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 . matrix a cairo_matrix_t dx X component of a distance vector. An in/out parameter dy Y component of a distance vector. An in/out parameter 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 . matrix a cairo_matrix_t x X position. An in/out parameter y Y position. An in/out parameter Since: 1.0 cairo_matrix_t 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; xx component of the affine transformation double yx; yx component of the affine transformation double xy; xy component of the affine transformation double yy; yy component of the affine transformation double x0; X translation component of the affine transformation double y0; Y translation component of the affine transformation Since: 1.0 cairo_t