Example 1. Directly modifying an image surface

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void
modify_image_surface(cairo_surface_t*surface)
{
unsignedchar*data;
intwidth,height,stride;
// flush to ensure all writing to the image was done
cairo_surface_flush(surface);
// modify the image
data=cairo_image_surface_get_data(surface);
width=cairo_image_surface_get_width(surface);
height=cairo_image_surface_get_height(surface);
stride=cairo_image_surface_get_stride(surface);
modify_image_data(data,width,height,stride);
// mark the image dirty so Cairo clears its caches.
cairo_surface_mark_dirty(surface);
}

cairo_surface_create_similar ()

cairo_surface_t *
cairo_surface_create_similar (cairo_surface_t *other,
 cairo_content_t content,
 int width,
 int height);

Create a new surface that is as compatible as possible with an existing surface. For example the new surface will have the same device scale, fallback resolution and font options as other . Generally, the new surface will also use the same backend as other , unless that is not possible for some reason. The type of the returned surface may be examined with cairo_surface_get_type().

Initially the surface contents are all 0 (transparent if contents have transparency, black otherwise.)

Use cairo_surface_create_similar_image() if you need an image surface which can be painted quickly to the target surface.

Since: 1.0

cairo_surface_create_similar_image ()

cairo_surface_t *
cairo_surface_create_similar_image (cairo_surface_t *other,
 cairo_format_t format,
 int width,
 int height);

Create a new image surface that is as compatible as possible for uploading to and the use in conjunction with an existing surface. However, this surface can still be used like any normal image surface. Unlike cairo_surface_create_similar() the new image surface won't inherit the device scale from other .

Initially the surface contents are all 0 (transparent if contents have transparency, black otherwise.)

Use cairo_surface_create_similar() if you don't need an image surface.

Since: 1.12

cairo_surface_create_for_rectangle ()

cairo_surface_t *
cairo_surface_create_for_rectangle (cairo_surface_t *target,
 double x,
 double y,
 double width,
 double height);

Create a new surface that is a rectangle within the target surface. All operations drawn to this surface are then clipped and translated onto the target surface. Nothing drawn via this sub-surface outside of its bounds is drawn onto the target surface, making this a useful method for passing constrained child surfaces to library routines that draw directly onto the parent surface, i.e. with no further backend allocations, double buffering or copies.

Since: 1.10

cairo_surface_reference ()

cairo_surface_t *
cairo_surface_reference (cairo_surface_t *surface);

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

Use cairo_surface_get_reference_count() to get the number of references to a cairo_surface_t.

Since: 1.0

cairo_surface_destroy ()

void
cairo_surface_destroy (cairo_surface_t *surface);

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

Since: 1.0

cairo_surface_status ()

cairo_status_t
cairo_surface_status (cairo_surface_t *surface);

Checks whether an error has previously occurred for this surface.

Since: 1.0

cairo_surface_finish ()

void
cairo_surface_finish (cairo_surface_t *surface);

This function finishes the surface and drops all references to external resources. For example, for the Xlib backend it means that cairo will no longer access the drawable, which can be freed. After calling cairo_surface_finish() the only valid operations on a surface are checking status, getting and setting user, referencing and destroying, and flushing and finishing it. Further drawing to the surface will not affect the surface but will instead trigger a CAIRO_STATUS_SURFACE_FINISHED error.

When the last call to cairo_surface_destroy() decreases the reference count to zero, cairo will call cairo_surface_finish() if it hasn't been called already, before freeing the resources associated with the surface.

Since: 1.0

cairo_surface_flush ()

void
cairo_surface_flush (cairo_surface_t *surface);

Do any pending drawing for the surface and also restore any temporary modifications cairo has made to the surface's state. This function must be called before switching from drawing on the surface with cairo to drawing on it directly with native APIs, or accessing its memory outside of Cairo. If the surface doesn't support direct access, then this function does nothing.

Since: 1.0

cairo_surface_get_device ()

cairo_device_t *
cairo_surface_get_device (cairo_surface_t *surface);

This function returns the device for a surface . See cairo_device_t.

Since: 1.10

cairo_surface_get_font_options ()

void
cairo_surface_get_font_options (cairo_surface_t *surface,
 cairo_font_options_t *options);

Retrieves the default font rendering options for the surface. This allows display surfaces to report the correct subpixel order for rendering on them, print surfaces to disable hinting of metrics and so forth. The result can then be used with cairo_scaled_font_create().

Since: 1.0

cairo_surface_get_content ()

cairo_content_t
cairo_surface_get_content (cairo_surface_t *surface);

This function returns the content type of surface which indicates whether the surface contains color and/or alpha information. See cairo_content_t.

Since: 1.2

cairo_surface_mark_dirty ()

void
cairo_surface_mark_dirty (cairo_surface_t *surface);

Tells cairo that drawing has been done to surface using means other than cairo, and that cairo should reread any cached areas. Note that you must call cairo_surface_flush() before doing such drawing.

Since: 1.0

cairo_surface_mark_dirty_rectangle ()

void
cairo_surface_mark_dirty_rectangle (cairo_surface_t *surface,
 int x,
 int y,
 int width,
 int height);

Like cairo_surface_mark_dirty(), but drawing has been done only to the specified rectangle, so that cairo can retain cached contents for other parts of the surface.

Any cached clip set on the surface will be reset by this function, to make sure that future cairo calls have the clip set that they expect.

Since: 1.0

cairo_surface_set_device_offset ()

void
cairo_surface_set_device_offset (cairo_surface_t *surface,
 double x_offset,
 double y_offset);

Sets an offset that is added to the device coordinates determined by the CTM when drawing to surface . One use case for this function is when we want to create a cairo_surface_t that redirects drawing for a portion of an onscreen surface to an offscreen surface in a way that is completely invisible to the user of the cairo API. Setting a transformation via cairo_translate() isn't sufficient to do this, since functions like cairo_device_to_user() will expose the hidden offset.

Note that the offset affects drawing to the surface as well as using the surface in a source pattern.

Since: 1.0

cairo_surface_get_device_offset ()

void
cairo_surface_get_device_offset (cairo_surface_t *surface,
 double *x_offset,
 double *y_offset);

This function returns the previous device offset set by cairo_surface_set_device_offset().

Since: 1.2

cairo_surface_get_device_scale ()

void
cairo_surface_get_device_scale (cairo_surface_t *surface,
 double *x_scale,
 double *y_scale);

This function returns the previous device scale set by cairo_surface_set_device_scale().

Since: 1.14

cairo_surface_set_device_scale ()

void
cairo_surface_set_device_scale (cairo_surface_t *surface,
 double x_scale,
 double y_scale);

Sets a scale that is multiplied to the device coordinates determined by the CTM when drawing to surface . One common use for this is to render to very high resolution display devices at a scale factor, so that code that assumes 1 pixel will be a certain size will still work. Setting a transformation via cairo_scale() isn't sufficient to do this, since functions like cairo_device_to_user() will expose the hidden scale.

Note that the scale affects drawing to the surface as well as using the surface in a source pattern.

Since: 1.14

cairo_surface_set_fallback_resolution ()

void
cairo_surface_set_fallback_resolution (cairo_surface_t *surface,
 double x_pixels_per_inch,
 double y_pixels_per_inch);

Set the horizontal and vertical resolution for image fallbacks.

When certain operations aren't supported natively by a backend, cairo will fallback by rendering operations to an image and then overlaying that image onto the output. For backends that are natively vector-oriented, this function can be used to set the resolution used for these image fallbacks, (larger values will result in more detailed images, but also larger file sizes).

Some examples of natively vector-oriented backends are the ps, pdf, and svg backends.

For backends that are natively raster-oriented, image fallbacks are still possible, but they are always performed at the native device resolution. So this function has no effect on those backends.

Note: The fallback resolution only takes effect at the time of completing a page (with cairo_show_page() or cairo_copy_page()) so there is currently no way to have more than one fallback resolution in effect on a single page.

The default fallback resolution is 300 pixels per inch in both dimensions.

Since: 1.2

cairo_surface_get_fallback_resolution ()

void
cairo_surface_get_fallback_resolution (cairo_surface_t *surface,
 double *x_pixels_per_inch,
 double *y_pixels_per_inch);

This function returns the previous fallback resolution set by cairo_surface_set_fallback_resolution(), or default fallback resolution if never set.

Since: 1.8

cairo_surface_get_type ()

cairo_surface_type_t
cairo_surface_get_type (cairo_surface_t *surface);

This function returns the type of the backend used to create a surface. See cairo_surface_type_t for available types.

Since: 1.2

cairo_surface_get_reference_count ()

unsigned int
cairo_surface_get_reference_count (cairo_surface_t *surface);

Returns the current reference count of surface .

Since: 1.4

cairo_surface_set_user_data ()

cairo_status_t
cairo_surface_set_user_data (cairo_surface_t *surface,
 const cairo_user_data_key_t *key,
 void *user_data,
 cairo_destroy_func_t destroy);

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

Since: 1.0

cairo_surface_get_user_data ()

void *
cairo_surface_get_user_data (cairo_surface_t *surface,
 const cairo_user_data_key_t *key);

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

Since: 1.0

cairo_surface_copy_page ()

void
cairo_surface_copy_page (cairo_surface_t *surface);

Emits the current page for backends that support multiple pages, but doesn't clear it, so that the contents of the current page will be retained for the next page. Use cairo_surface_show_page() if you want to get an empty page after the emission.

There is a convenience function for this that takes a cairo_t, namely cairo_copy_page().

Since: 1.6

cairo_surface_show_page ()

void
cairo_surface_show_page (cairo_surface_t *surface);

Emits and clears the current page for backends that support multiple pages. Use cairo_surface_copy_page() if you don't want to clear the page.

There is a convenience function for this that takes a cairo_t, namely cairo_show_page().

Since: 1.6

cairo_surface_has_show_text_glyphs ()

cairo_bool_t
cairo_surface_has_show_text_glyphs (cairo_surface_t *surface);

Returns whether the surface supports sophisticated cairo_show_text_glyphs() operations. That is, whether it actually uses the provided text and cluster data to a cairo_show_text_glyphs() call.

Note: Even if this function returns FALSE, a cairo_show_text_glyphs() operation targeted at surface will still succeed. It just will act like a cairo_show_glyphs() operation. Users can use this function to avoid computing UTF-8 text and cluster mapping if the target surface does not use it.

Since: 1.8

cairo_surface_set_mime_data ()

cairo_status_t
cairo_surface_set_mime_data (cairo_surface_t *surface,
 const char *mime_type,
 const unsigned char *data,
 unsigned long  length,
 cairo_destroy_func_t destroy,
 void *closure);

Attach an image in the format mime_type to surface . To remove the data from a surface, call this function with same mime type and NULL for data .

The attached image (or filename) data can later be used by backends which support it (currently: PDF, PS, SVG and Win32 Printing surfaces) to emit this data instead of making a snapshot of the surface . This approach tends to be faster and requires less memory and disk space.

The recognized MIME types are the following: CAIRO_MIME_TYPE_JPEG, CAIRO_MIME_TYPE_PNG, CAIRO_MIME_TYPE_JP2, CAIRO_MIME_TYPE_URI, CAIRO_MIME_TYPE_UNIQUE_ID, CAIRO_MIME_TYPE_JBIG2, CAIRO_MIME_TYPE_JBIG2_GLOBAL, CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID, CAIRO_MIME_TYPE_CCITT_FAX, CAIRO_MIME_TYPE_CCITT_FAX_PARAMS.

See corresponding backend surface docs for details about which MIME types it can handle. Caution: the associated MIME data will be discarded if you draw on the surface afterwards. Use this function with care.

Even if a backend supports a MIME type, that does not mean cairo will always be able to use the attached MIME data. For example, if the backend does not natively support the compositing operation used to apply the MIME data to the backend. In that case, the MIME data will be ignored. Therefore, to apply an image in all cases, it is best to create an image surface which contains the decoded image data and then attach the MIME data to that. This ensures the image will always be used while still allowing the MIME data to be used whenever possible.

Since: 1.10

cairo_surface_get_mime_data ()

void
cairo_surface_get_mime_data (cairo_surface_t *surface,
 const char *mime_type,
 const unsigned char **data,
 unsigned long *length);

Return mime data previously attached to surface using the specified mime type. If no data has been attached with the given mime type, data is set NULL.

Since: 1.10

cairo_surface_supports_mime_type ()

cairo_bool_t
cairo_surface_supports_mime_type (cairo_surface_t *surface,
 const char *mime_type);

Return whether surface supports mime_type .

Since: 1.12

cairo_surface_map_to_image ()

cairo_surface_t *
cairo_surface_map_to_image (cairo_surface_t *surface,
 const cairo_rectangle_int_t *extents);

Returns an image surface that is the most efficient mechanism for modifying the backing store of the target surface. The region retrieved may be limited to the extents or NULL for the whole surface

Note, the use of the original surface as a target or source whilst it is mapped is undefined. The result of mapping the surface multiple times is undefined. Calling cairo_surface_destroy() or cairo_surface_finish() on the resulting image surface results in undefined behavior. Changing the device transform of the image surface or of surface before the image surface is unmapped results in undefined behavior.

Since: 1.12

cairo_surface_unmap_image ()

void
cairo_surface_unmap_image (cairo_surface_t *surface,
 cairo_surface_t *image);

Unmaps the image surface as returned from cairo_surface_map_to_image().

The content of the image will be uploaded to the target surface. Afterwards, the image is destroyed.

Using an image surface which wasn't returned by cairo_surface_map_to_image() results in undefined behavior.

Since: 1.12

CAIRO_HAS_MIME_SURFACE

#define CAIRO_HAS_MIME_SURFACE

Unused symbol, always defined.

Since: 1.12

CAIRO_MIME_TYPE_CCITT_FAX

#define CAIRO_MIME_TYPE_CCITT_FAX "image/g3fax"

Group 3 or Group 4 CCITT facsimile encoding (International Telecommunication Union, Recommendations T.4 and T.6.)

Since: 1.16

CAIRO_MIME_TYPE_CCITT_FAX_PARAMS

#define CAIRO_MIME_TYPE_CCITT_FAX_PARAMS "application/x-cairo.ccitt.params"

Decode parameters for Group 3 or Group 4 CCITT facsimile encoding. See CCITT Fax Images.

Since: 1.16

CAIRO_MIME_TYPE_EPS

#define CAIRO_MIME_TYPE_EPS "application/postscript"

Encapsulated PostScript file. Encapsulated PostScript File Format Specification

Since: 1.16

CAIRO_MIME_TYPE_EPS_PARAMS

#define CAIRO_MIME_TYPE_EPS_PARAMS "application/x-cairo.eps.params"

Embedding parameters Encapsulated PostScript data. See Embedding EPS files.

Since: 1.16

CAIRO_MIME_TYPE_JBIG2

#define CAIRO_MIME_TYPE_JBIG2 "application/x-cairo.jbig2"

Joint Bi-level Image Experts Group image coding standard (ISO/IEC 11544).

Since: 1.14

CAIRO_MIME_TYPE_JBIG2_GLOBAL

#define CAIRO_MIME_TYPE_JBIG2_GLOBAL "application/x-cairo.jbig2-global"

Joint Bi-level Image Experts Group image coding standard (ISO/IEC 11544) global segment.

Since: 1.14

CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID

#define CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID "application/x-cairo.jbig2-global-id"

An unique identifier shared by a JBIG2 global segment and all JBIG2 images that depend on the global segment.

Since: 1.14

CAIRO_MIME_TYPE_JP2

#define CAIRO_MIME_TYPE_JP2 "image/jp2"

The Joint Photographic Experts Group (JPEG) 2000 image coding standard (ISO/IEC 15444-1).

Since: 1.10

CAIRO_MIME_TYPE_JPEG

#define CAIRO_MIME_TYPE_JPEG "image/jpeg"

The Joint Photographic Experts Group (JPEG) image coding standard (ISO/IEC 10918-1).

Since: 1.10

CAIRO_MIME_TYPE_PNG

#define CAIRO_MIME_TYPE_PNG "image/png"

The Portable Network Graphics image file format (ISO/IEC 15948).

Since: 1.10

CAIRO_MIME_TYPE_URI

#define CAIRO_MIME_TYPE_URI "text/x-uri"

URI for an image file (unofficial MIME type).

Since: 1.10

CAIRO_MIME_TYPE_UNIQUE_ID

#define CAIRO_MIME_TYPE_UNIQUE_ID "application/x-cairo.uuid"

Unique identifier for a surface (cairo specific MIME type). All surfaces with the same unique identifier will only be embedded once.

Since: 1.12

cairo_surface_t

typedef struct _cairo_surface cairo_surface_t;

A cairo_surface_t represents an image, either as the destination of a drawing operation or as source when drawing onto another surface. To draw to a cairo_surface_t, create a cairo context with the surface as the target, using cairo_create().

There are different subtypes of cairo_surface_t for different drawing backends; for example, cairo_image_surface_create() creates a bitmap image in memory. The type of a surface can be queried with cairo_surface_get_type().

The initial contents of a surface after creation depend upon the manner of its creation. If cairo creates the surface and backing storage for the user, it will be initially cleared; for example, cairo_image_surface_create() and cairo_surface_create_similar(). Alternatively, if the user passes in a reference to some backing storage and asks cairo to wrap that in a cairo_surface_t, then the contents are not modified; for example, cairo_image_surface_create_for_data() and cairo_xlib_surface_create().

Memory management of cairo_surface_t is done with cairo_surface_reference() and cairo_surface_destroy().

Since: 1.0

enum cairo_content_t

cairo_content_t is used to describe the content that a surface will contain, whether color information, alpha information (translucence vs. opacity), or both.

Note: The large values here are designed to keep cairo_content_t values distinct from cairo_format_t values so that the implementation can detect the error if users confuse the two types.

Since: 1.0

enum cairo_surface_type_t

cairo_surface_type_t is used to describe the type of a given surface. The surface types are also known as "backends" or "surface backends" within cairo.

The type of a surface is determined by the function used to create it, which will generally be of the form cairo_type_surface_create(), (though see cairo_surface_create_similar() as well).

The surface type can be queried with cairo_surface_get_type()

The various cairo_surface_t functions can be used with surfaces of any type, but some backends also provide type-specific functions that must only be called with a surface of the appropriate type. These functions have names that begin with cairo_type_surface such as cairo_image_surface_get_width().

The behavior of calling a type-specific function with a surface of the wrong type is undefined.

New entries may be added in future versions.

Since: 1.2