Patterns

## Patterns Patterns — Gradients and filtered sources |

## Synopsis

    typedef     cairo_pattern_t;
    void        cairo_pattern_add_color_stop_rgb
                                                (cairo_pattern_t *pattern,
                                                 double offset,
                                                 double red,
                                                 double green,
                                                 double blue);
    void        cairo_pattern_add_color_stop_rgba
                                                (cairo_pattern_t *pattern,
                                                 double offset,
                                                 double red,
                                                 double green,
                                                 double blue,
                                                 double alpha);
    cairo_pattern_t* cairo_pattern_create_rgb   (double red,
                                                 double green,
                                                 double blue);
    cairo_pattern_t* cairo_pattern_create_rgba  (double red,
                                                 double green,
                                                 double blue,
                                                 double alpha);
    cairo_pattern_t* cairo_pattern_create_for_surface
                                                (cairo_surface_t *surface);
    cairo_pattern_t* cairo_pattern_create_linear
                                                (double x0,
                                                 double y0,
                                                 double x1,
                                                 double y1);
    cairo_pattern_t* cairo_pattern_create_radial
                                                (double cx0,
                                                 double cy0,
                                                 double radius0,
                                                 double cx1,
                                                 double cy1,
                                                 double radius1);
    void        cairo_pattern_destroy           (cairo_pattern_t *pattern);
    cairo_pattern_t* cairo_pattern_reference    (cairo_pattern_t *pattern);
    cairo_status_t cairo_pattern_status         (cairo_pattern_t *pattern);
    enum        cairo_extend_t;
    void        cairo_pattern_set_extend        (cairo_pattern_t *pattern,
                                                 cairo_extend_t extend);
    cairo_extend_t cairo_pattern_get_extend     (cairo_pattern_t *pattern);
    enum        cairo_filter_t;
    void        cairo_pattern_set_filter        (cairo_pattern_t *pattern,
                                                 cairo_filter_t filter);
    cairo_filter_t cairo_pattern_get_filter     (cairo_pattern_t *pattern);
    void        cairo_pattern_set_matrix        (cairo_pattern_t *pattern,
                                                 const cairo_matrix_t *matrix);
    void        cairo_pattern_get_matrix        (cairo_pattern_t *pattern,
                                                 cairo_matrix_t *matrix);
    enum        cairo_pattern_type_t;
    cairo_pattern_type_t cairo_pattern_get_type (cairo_pattern_t *pattern);

## Description

## Details

### cairo_pattern_t

    typedef struct _cairo_pattern cairo_pattern_t;

### 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()`.

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`.

`pattern` : | a cairo_pattern_t
`offset` : | an offset in the range [0.0 .. 1.0]
`red` : | red component of color
`green` : | green component of color
`blue` : | blue component of color

### 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()`.

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`.

`pattern` : | a cairo_pattern_t
`offset` : | an offset in the range [0.0 .. 1.0]
`red` : | red component of color
`green` : | green component of color
`blue` : | blue component of color
`alpha` : | alpha component of color

### 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.

`red` : | red component of the color
`green` : | green component of the color
`blue` : | blue component of the color
Returns : | the newly created cairo_pattern_t if succesful, or an error pattern in case of no memory. The caller owns the returned object and should call `cairo_pattern_destroy()` when finished with it. This function will always return a valid pointer, but if an error occurred the pattern status will be set to an error. To inspect the status of a pattern use `cairo_pattern_status()`.

### 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.

`red` : | red component of the color
`green` : | green component of the color
`blue` : | blue component of the color
`alpha` : | alpha component of the color
Returns : | the newly created cairo_pattern_t if succesful, or an error pattern in case of no memory. The caller owns the returned object and should call `cairo_pattern_destroy()` when finished with it. This function will always return a valid pointer, but if an error occurred the pattern status will be set to an error. To inspect the status of a pattern use `cairo_pattern_status()`.

### 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.

`surface` : | the surface
Returns : | the newly created cairo_pattern_t if succesful, or an error pattern in case of no memory. The caller owns the returned object and should call `cairo_pattern_destroy()` when finished with it. This function will always return a valid pointer, but if an error occurred the pattern status will be set to an error. To inspect the status of a pattern use `cairo_pattern_status()`.

### 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()`.

`x0` : | x coordinate of the start point
`y0` : | y coordinate of the start point
`x1` : | x coordinate of the end point
`y1` : | y coordinate of the end point
Returns : | the newly created cairo_pattern_t if succesful, or an error pattern in case of no memory. The caller owns the returned object and should call `cairo_pattern_destroy()` when finished with it. This function will always return a valid pointer, but if an error occurred the pattern status will be set to an error. To inspect the status of a pattern use `cairo_pattern_status()`.

### 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 (x0, y0, c0) and (x1, y1, c0). 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()`.

`cx0` : | x coordinate for the center of the start circle
`cy0` : | y coordinate for the center of the start circle
`radius0` : | radius of the start cirle
`cx1` : | x coordinate for the center of the end circle
`cy1` : | y coordinate for the center of the end circle
`radius1` : | radius of the end cirle
Returns : | the newly created cairo_pattern_t if succesful, or an error pattern in case of no memory. The caller owns the returned object and should call `cairo_pattern_destroy()` when finished with it. This function will always return a valid pointer, but if an error occurred the pattern status will be set to an error. To inspect the status of a pattern use `cairo_pattern_status()`.

### 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()`.

`pattern` : | a cairo_pattern_t

### 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.

`pattern` : | a cairo_pattern_t
Returns : | the referenced cairo_pattern_t.

### cairo_pattern_status ()

    cairo_status_t cairo_pattern_status         (cairo_pattern_t *pattern);

Checks whether an error has previously occurred for this pattern.

`pattern` : | a cairo_pattern_t
Returns : | `CAIRO_STATUS_SUCCESS`, `CAIRO_STATUS_NO_MEMORY`, or `CAIRO_STATUS_PATTERN_TYPE_MISMATCH`.

### 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 the area outside of a pattern will be drawn.

New entries may be added in future versions.

`CAIRO_EXTEND_NONE` | pixels outside of the source pattern are fully transparent
`CAIRO_EXTEND_REPEAT` | the pattern is tiled by repeating
`CAIRO_EXTEND_REFLECT` | the pattern is tiled by reflecting at the edges (not implemented for surface patterns currently)
`CAIRO_EXTEND_PAD` | pixels outside of the pattern copy the closest pixel from the source (Since 1.2; not implemented for surface patterns currently)

### 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.

`pattern` : | a cairo_pattern_t
`extend` : | a cairo_extend_t describing how the area outside of the pattern will be drawn

### 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.

`pattern` : | a cairo_pattern_t
Returns : | the current extend strategy used for drawing the pattern.

### 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_pattern_set_filter ()

    void        cairo_pattern_set_filter        (cairo_pattern_t *pattern,
                                                 cairo_filter_t filter);

`pattern` : |
`filter` : |

### cairo_pattern_get_filter ()

    cairo_filter_t cairo_pattern_get_filter     (cairo_pattern_t *pattern);

`pattern` : |
Returns : |

### 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()`.

`pattern` : | a cairo_pattern_t
`matrix` : | a cairo_matrix_t

### 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`.

`pattern` : | a cairo_pattern_t
`matrix` : | return value for the 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 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.

`CAIRO_PATTERN_TYPE_SOLID` | The pattern is a solid (uniform) color. It may be opaque or translucent.
`CAIRO_PATTERN_TYPE_SURFACE` | The pattern is a based on a surface (an image).
`CAIRO_PATTERN_TYPE_LINEAR` | The pattern is a linear gradient.
`CAIRO_PATTERN_TYPE_RADIAL` | The pattern is a radial gradient.

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.

`pattern` : | a cairo_pattern_t
Returns : | The type of `pattern`.

Since 1.2