cairo_pattern_t

typedef struct _cairo_pattern cairo_pattern_t;

A cairo_pattern_t represents a source when drawing onto a surface. There are different subtypes of cairo_pattern_t, for different types of sources; for example, cairo_pattern_create_rgb() creates a pattern for a solid opaque color.

Other than various cairo_pattern_create_type() functions, some of the pattern types can be implicitly created using various cairo_set_source_type() functions; for example cairo_set_source_rgb().

The type of a pattern can be queried with cairo_pattern_get_type().

Memory management of cairo_pattern_t is done with cairo_pattern_reference() and cairo_pattern_destroy().

cairo_pattern_add_color_stop_rgb ()

void                cairo_pattern_add_color_stop_rgb    (cairo_pattern_t *pattern,
                                                         double offset,
                                                         double red,
                                                         double green,
                                                         double blue);

Adds an opaque color stop to a gradient pattern. The offset specifies the location along the gradient's control vector. For example, a linear gradient's control vector is from (x0,y0) to (x1,y1) while a radial gradient's control vector is from any point on the start circle to the corresponding point on the end circle.

The color is specified in the same way as in cairo_set_source_rgb().

If two (or more) stops are specified with identical offset values, they will be sorted according to the order in which the stops are added, (stops added earlier will compare less than stops added later). This can be useful for reliably making sharp color transitions instead of the typical blend.

Note: If the pattern is not a gradient pattern, (eg. a linear or radial pattern), then the pattern will be put into an error status with a status of CAIRO_STATUS_PATTERN_TYPE_MISMATCH.

cairo_pattern_add_color_stop_rgba ()

void                cairo_pattern_add_color_stop_rgba   (cairo_pattern_t *pattern,
                                                         double offset,
                                                         double red,
                                                         double green,
                                                         double blue,
                                                         double alpha);

Adds a translucent color stop to a gradient pattern. The offset specifies the location along the gradient's control vector. For example, a linear gradient's control vector is from (x0,y0) to (x1,y1) while a radial gradient's control vector is from any point on the start circle to the corresponding point on the end circle.

The color is specified in the same way as in cairo_set_source_rgba().

If two (or more) stops are specified with identical offset values, they will be sorted according to the order in which the stops are added, (stops added earlier will compare less than stops added later). This can be useful for reliably making sharp color transitions instead of the typical blend.

Note: If the pattern is not a gradient pattern, (eg. a linear or radial pattern), then the pattern will be put into an error status with a status of CAIRO_STATUS_PATTERN_TYPE_MISMATCH.

cairo_pattern_get_color_stop_count ()

cairo_status_t      cairo_pattern_get_color_stop_count  (cairo_pattern_t *pattern,
                                                         int *count);

Gets the number of color stops specified in the given gradient pattern.

Since 1.4

cairo_pattern_get_color_stop_rgba ()

cairo_status_t      cairo_pattern_get_color_stop_rgba   (cairo_pattern_t *pattern,
                                                         int index,
                                                         double *offset,
                                                         double *red,
                                                         double *green,
                                                         double *blue,
                                                         double *alpha);

Gets the color and offset information at the given index for a gradient pattern. Values of index are 0 to 1 less than the number returned by cairo_pattern_get_color_stop_count().

Since 1.4

cairo_pattern_create_rgb ()

cairo_pattern_t *   cairo_pattern_create_rgb            (double red,
                                                         double green,
                                                         double blue);

Creates a new cairo_pattern_t corresponding to an opaque color. The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cairo_pattern_create_rgba ()

cairo_pattern_t *   cairo_pattern_create_rgba           (double red,
                                                         double green,
                                                         double blue,
                                                         double alpha);

Creates a new cairo_pattern_t corresponding to a translucent color. The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cairo_pattern_get_rgba ()

cairo_status_t      cairo_pattern_get_rgba              (cairo_pattern_t *pattern,
                                                         double *red,
                                                         double *green,
                                                         double *blue,
                                                         double *alpha);

Gets the solid color for a solid color pattern.

Since 1.4

cairo_pattern_create_for_surface ()

cairo_pattern_t *   cairo_pattern_create_for_surface    (cairo_surface_t *surface);

Create a new cairo_pattern_t for the given surface.

cairo_pattern_get_surface ()

cairo_status_t      cairo_pattern_get_surface           (cairo_pattern_t *pattern,
                                                         cairo_surface_t **surface);

Gets the surface of a surface pattern. The reference returned in surface is owned by the pattern; the caller should call cairo_surface_reference() if the surface is to be retained.

Since 1.4

cairo_pattern_create_linear ()

cairo_pattern_t *   cairo_pattern_create_linear         (double x0,
                                                         double y0,
                                                         double x1,
                                                         double y1);

Create a new linear gradient cairo_pattern_t along the line defined by (x0, y0) and (x1, y1). Before using the gradient pattern, a number of color stops should be defined using cairo_pattern_add_color_stop_rgb() or cairo_pattern_add_color_stop_rgba().

Note: The coordinates here are in pattern space. For a new pattern, pattern space is identical to user space, but the relationship between the spaces can be changed with cairo_pattern_set_matrix().

cairo_pattern_get_linear_points ()

cairo_status_t      cairo_pattern_get_linear_points     (cairo_pattern_t *pattern,
                                                         double *x0,
                                                         double *y0,
                                                         double *x1,
                                                         double *y1);

Gets the gradient endpoints for a linear gradient.

Since 1.4

cairo_pattern_create_radial ()

cairo_pattern_t *   cairo_pattern_create_radial         (double cx0,
                                                         double cy0,
                                                         double radius0,
                                                         double cx1,
                                                         double cy1,
                                                         double radius1);

Creates a new radial gradient cairo_pattern_t between the two circles defined by (cx0, cy0, radius0) and (cx1, cy1, radius1). Before using the gradient pattern, a number of color stops should be defined using cairo_pattern_add_color_stop_rgb() or cairo_pattern_add_color_stop_rgba().

Note: The coordinates here are in pattern space. For a new pattern, pattern space is identical to user space, but the relationship between the spaces can be changed with cairo_pattern_set_matrix().

cairo_pattern_get_radial_circles ()

cairo_status_t      cairo_pattern_get_radial_circles    (cairo_pattern_t *pattern,
                                                         double *x0,
                                                         double *y0,
                                                         double *r0,
                                                         double *x1,
                                                         double *y1,
                                                         double *r1);

Gets the gradient endpoint circles for a radial gradient, each specified as a center coordinate and a radius.

Since 1.4

cairo_pattern_reference ()

cairo_pattern_t *   cairo_pattern_reference             (cairo_pattern_t *pattern);

Increases the reference count on pattern by one. This prevents pattern from being destroyed until a matching call to cairo_pattern_destroy() is made.

The number of references to a cairo_pattern_t can be get using cairo_pattern_get_reference_count().

cairo_pattern_destroy ()

void                cairo_pattern_destroy               (cairo_pattern_t *pattern);

Decreases the reference count on pattern by one. If the result is zero, then pattern and all associated resources are freed. See cairo_pattern_reference().

cairo_pattern_status ()

cairo_status_t      cairo_pattern_status                (cairo_pattern_t *pattern);

Checks whether an error has previously occurred for this pattern.

enum cairo_extend_t

typedef enum _cairo_extend {
    CAIRO_EXTEND_NONE,
    CAIRO_EXTEND_REPEAT,
    CAIRO_EXTEND_REFLECT,
    CAIRO_EXTEND_PAD
} cairo_extend_t;

cairo_extend_t is used to describe how pattern color/alpha will be determined for areas "outside" the pattern's natural area, (for example, outside the surface bounds or outside the gradient geometry).

The default extend mode is CAIRO_EXTEND_NONE for surface patterns and CAIRO_EXTEND_PAD for gradient patterns.

New entries may be added in future versions.

cairo_pattern_set_extend ()

void                cairo_pattern_set_extend            (cairo_pattern_t *pattern,
                                                         cairo_extend_t extend);

Sets the mode to be used for drawing outside the area of a pattern. See cairo_extend_t for details on the semantics of each extend strategy.

The default extend mode is CAIRO_EXTEND_NONE for surface patterns and CAIRO_EXTEND_PAD for gradient patterns.

cairo_pattern_get_extend ()

cairo_extend_t      cairo_pattern_get_extend            (cairo_pattern_t *pattern);

Gets the current extend mode for a pattern. See cairo_extend_t for details on the semantics of each extend strategy.

enum cairo_filter_t

typedef enum _cairo_filter {
    CAIRO_FILTER_FAST,
    CAIRO_FILTER_GOOD,
    CAIRO_FILTER_BEST,
    CAIRO_FILTER_NEAREST,
    CAIRO_FILTER_BILINEAR,
    CAIRO_FILTER_GAUSSIAN
} cairo_filter_t;

cairo_filter_t is used to indicate what filtering should be applied when reading pixel values from patterns. See cairo_pattern_set_source() for indicating the desired filter to be used with a particular pattern.

cairo_pattern_set_filter ()

void                cairo_pattern_set_filter            (cairo_pattern_t *pattern,
                                                         cairo_filter_t filter);

Sets the filter to be used for resizing when using this pattern. See cairo_filter_t for details on each filter.

* Note that you might want to control filtering even when you do not have an explicit cairo_pattern_t object, (for example when using cairo_set_source_surface()). In these cases, it is convenient to use cairo_get_source() to get access to the pattern that cairo creates implicitly. For example:

cairo_set_source_surface (cr, image, x, y);
cairo_pattern_set_filter (cairo_get_source (cr), %CAIRO_FILTER_NEAREST);

cairo_pattern_get_filter ()

cairo_filter_t      cairo_pattern_get_filter            (cairo_pattern_t *pattern);

Gets the current filter for a pattern. See cairo_filter_t for details on each filter.

cairo_pattern_set_matrix ()

void                cairo_pattern_set_matrix            (cairo_pattern_t *pattern,
                                                         const cairo_matrix_t *matrix);

Sets the pattern's transformation matrix to matrix. This matrix is a transformation from user space to pattern space.

When a pattern is first created it always has the identity matrix for its transformation matrix, which means that pattern space is initially identical to user space.

Important: Please note that the direction of this transformation matrix is from user space to pattern space. This means that if you imagine the flow from a pattern to user space (and on to device space), then coordinates in that flow will be transformed by the inverse of the pattern matrix.

For example, if you want to make a pattern appear twice as large as it does by default the correct code to use is:

cairo_matrix_init_scale (&matrix, 0.5, 0.5);
cairo_pattern_set_matrix (pattern, &matrix);

Meanwhile, using values of 2.0 rather than 0.5 in the code above would cause the pattern to appear at half of its default size.

Also, please note the discussion of the user-space locking semantics of cairo_set_source().

cairo_pattern_get_matrix ()

void                cairo_pattern_get_matrix            (cairo_pattern_t *pattern,
                                                         cairo_matrix_t *matrix);

Stores the pattern's transformation matrix into matrix.

enum cairo_pattern_type_t

typedef enum _cairo_pattern_type {
    CAIRO_PATTERN_TYPE_SOLID,
    CAIRO_PATTERN_TYPE_SURFACE,
    CAIRO_PATTERN_TYPE_LINEAR,
    CAIRO_PATTERN_TYPE_RADIAL
} cairo_pattern_type_t;

cairo_pattern_type_t is used to describe the type of a given pattern.

The type of a pattern is determined by the function used to create it. The cairo_pattern_create_rgb() and cairo_pattern_create_rgba() functions create SOLID patterns. The remaining cairo_pattern_create functions map to pattern types in obvious ways.

The pattern type can be queried with cairo_pattern_get_type()

Most cairo_pattern_t functions can be called with a pattern of any type, (though trying to change the extend or filter for a solid pattern will have no effect). A notable exception is cairo_pattern_add_color_stop_rgb() and cairo_pattern_add_color_stop_rgba() which must only be called with gradient patterns (either LINEAR or RADIAL). Otherwise the pattern will be shutdown and put into an error state.

New entries may be added in future versions.

Since 1.2

cairo_pattern_get_type ()

cairo_pattern_type_t  cairo_pattern_get_type            (cairo_pattern_t *pattern);

This function returns the type a pattern. See cairo_pattern_type_t for available types.

Since 1.2

cairo_pattern_get_reference_count ()

unsigned int        cairo_pattern_get_reference_count   (cairo_pattern_t *pattern);

Returns the current reference count of pattern.

Since 1.4

cairo_pattern_set_user_data ()

cairo_status_t      cairo_pattern_set_user_data         (cairo_pattern_t *pattern,
                                                         const cairo_user_data_key_t *key,
                                                         void *user_data,
                                                         cairo_destroy_func_t destroy);

Attach user data to pattern. To remove user data from a surface, call this function with the key that was used to set it and NULL for data.

Since 1.4

cairo_pattern_get_user_data ()

void *              cairo_pattern_get_user_data         (cairo_pattern_t *pattern,
                                                         const cairo_user_data_key_t *key);

Return user data previously attached to pattern using the specified key. If no user data has been attached with the given key this function returns NULL.

Since 1.4