Image surfaces provide the ability to render to memory buffers either allocated by cairo or by the calling code. More...

#include <cairomm/surface.h>

Inheritance diagram for Cairo::ImageSurface:

[legend]

Public Member Functions
	ImageSurface (cairo_surface_t *cobject, bool has_reference=false)
	Create a C++ wrapper for the C instance. More...

	~ImageSurface () override

int	get_width () const
	Gets the width of the ImageSurface in pixels. More...

int	get_height () const
	Gets the height of the ImageSurface in pixels. More...

Format	get_format () const
	Gets the format of the surface. More...

int	get_stride () const
	Returns the stride of the image surface in bytes (or 0 if surface is not an image surface). More...


unsigned char *	get_data ()
	Get a pointer to the data of the image surface, for direct inspection or modification. More...

const unsigned char *	get_data () const

Public Member Functions inherited from Cairo::Surface
	Surface (cairo_surface_t *cobject, bool has_reference=false)
	Create a C++ wrapper for the C instance. More...

	Surface (const Surface &)=delete

Surface &	operator= (const Surface &)=delete

virtual	~Surface ()

const unsigned char *	get_mime_data (const std::string & mime_type, unsigned long & length)
	Return mime data previously attached to surface using the specified mime type. More...

void	set_mime_data (const std::string & mime_type, unsigned char *data, unsigned long length, const SlotDestroy & slot_destroy)
	Attach an image in the format mime_type to surface. More...

void	unset_mime_data (const std::string & mime_type)
	Remove the data from a surface. More...

void	get_font_options (FontOptions & options) const
	Retrieves the default font rendering options for the surface. More...

void	finish ()
	This function finishes the surface and drops all references to external resources. More...

void	flush ()
	Do any pending drawing for the surface and also restore any temporary modifications cairo has made to the surface's state. More...

void	mark_dirty ()
	Tells cairo to consider the data buffer dirty. More...

void	mark_dirty (int x, int y, int width, int height)
	Marks a rectangular area of the given surface dirty. More...

void	set_device_offset (double x_offset, double y_offset)
	Sets an offset that is added to the device coordinates determined by the CTM when drawing to surface. More...

void	get_device_offset (double & x_offset, double & y_offset) const
	Returns a previous device offset set by set_device_offset(). More...

void	set_device_scale (double x_scale, double y_scale)
	Sets a scale that is multiplied to the device coordinates determined by the CTM when drawing to surface. More...

void	set_device_scale (double scale)
	Sets x and y scale to the same value. More...

void	get_device_scale (double & x_scale, double & y_scale) const
	Returns a previous device scale set by set_device_scale(). More...

double	get_device_scale () const
	Returns the x and y average of a previous device scale set by set_device_scale(). More...

void	set_fallback_resolution (double x_pixels_per_inch, double y_pixels_per_inch)
	Set the horizontal and vertical resolution for image fallbacks. More...

void	get_fallback_resolution (double & x_pixels_per_inch, double & y_pixels_per_inch) const
	This function returns the previous fallback resolution set by set_fallback_resolution(), or default fallback resolution if never set. More...

Type	get_type () const

Content	get_content () const
	This function returns the content type of surface which indicates whether the surface contains color and/or alpha information. More...

void	copy_page ()
	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. More...

void	show_page ()
	Emits and clears the current page for backends that support multiple pages. More...

bool	has_show_text_glyphs () const
	Returns whether the surface supports sophisticated Context::show_text_glyphs() operations. More...

void	write_to_png (const std::string & filename)
	Writes the contents of surface to a new file filename as a PNG image. More...

void	write_to_png_stream (const SlotWriteFunc & write_func)
	Writes the Surface to the write function. More...

RefPtr< Device >	get_device ()
	This function returns the device for a surface. More...

cobject *	cobj ()
	Provides acces to the underlying C cairo surface. More...

const cobject *	cobj () const
	Provides acces to the underlying C cairo surface. More...

Static Public Member Functions
static int	format_stride_for_width (Format format, int width)
	This function provides a stride value that will respect all alignment requirements of the accelerated image-rendering code within cairo. More...

static RefPtr< ImageSurface >	create (Format format, int width, int height)
	Creates an image surface of the specified format and dimensions. More...

static RefPtr< ImageSurface >	create (unsigned char *data, Format format, int width, int height, int stride)
	Creates an image surface for the provided pixel data. More...

static RefPtr< ImageSurface >	create_from_png (std::string filename)
	Creates a new image surface and initializes the contents to the given PNG file. More...

static RefPtr< ImageSurface >	create_from_png_stream (const SlotReadFunc & read_func)
	Creates a new image surface from PNG data read incrementally via the read_func function. More...

Static Public Member Functions inherited from Cairo::Surface
static RefPtr< Surface >	create (const RefPtr< Surface > other, Content content, int width, int height)
	Create a new surface that is as compatible as possible with an existing surface. More...

static RefPtr< Surface >	create (const RefPtr< Surface > & target, double x, double y, double width, double height)
	Create a new surface that is a rectangle within the target surface. More...

Additional Inherited Members
Public Types inherited from Cairo::Surface
enum class	Type { IMAGE = CAIRO_SURFACE_TYPE_IMAGE , PDF = CAIRO_SURFACE_TYPE_PDF , PS = CAIRO_SURFACE_TYPE_PS , XLIB = CAIRO_SURFACE_TYPE_XLIB , XCB = CAIRO_SURFACE_TYPE_XCB , GLITZ = CAIRO_SURFACE_TYPE_GLITZ , QUARTZ = CAIRO_SURFACE_TYPE_QUARTZ , WIN32 = CAIRO_SURFACE_TYPE_WIN32 , WIN32_SURFACE = CAIRO_SURFACE_TYPE_WIN32 , BEOS = CAIRO_SURFACE_TYPE_BEOS , DIRECTFB = CAIRO_SURFACE_TYPE_DIRECTFB , SVG = CAIRO_SURFACE_TYPE_SVG , OS2 = CAIRO_SURFACE_TYPE_OS2 , WIN32_PRINTING = CAIRO_SURFACE_TYPE_WIN32_PRINTING , QUARTZ_IMAGE = CAIRO_SURFACE_TYPE_QUARTZ_IMAGE , SCRIPT = CAIRO_SURFACE_TYPE_SCRIPT , QT = CAIRO_SURFACE_TYPE_QT , RECORDING = CAIRO_SURFACE_TYPE_RECORDING , VG = CAIRO_SURFACE_TYPE_VG , GL = CAIRO_SURFACE_TYPE_GL , DRM = CAIRO_SURFACE_TYPE_DRM , TEE = CAIRO_SURFACE_TYPE_TEE , XML = CAIRO_SURFACE_TYPE_XML , SKIA = CAIRO_SURFACE_TYPE_SKIA , SUBSURFACE = CAIRO_SURFACE_TYPE_SUBSURFACE }
	Cairo::Surface::Type is used to describe the type of a given surface. More...

enum class	Format { ARGB32 = CAIRO_FORMAT_ARGB32 , RGB24 = CAIRO_FORMAT_RGB24 , A8 = CAIRO_FORMAT_A8 , A1 = CAIRO_FORMAT_A1 , RGB16_565 = CAIRO_FORMAT_RGB16_565 }
	Cairo::Surface::Format is used to identify the memory format of image data. More...

typedef sigc::slot< ErrorStatus(const unsigned char *, unsigned int)>	SlotWriteFunc
	For example: `ErrorStatus my_write_func(unsigned char* data, unsigned int length);` More...

typedef sigc::slot< ErrorStatus(unsigned char *, unsigned int)>	SlotReadFunc
	This is the type of function which is called when a backend needs to read data from an input stream. More...

typedef sigc::slot< void()>	SlotDestroy
	For instance, void on_destroy();. More...

typedef cairo_surface_t	cobject
	The underlying C cairo surface type. More...

Protected Attributes inherited from Cairo::Surface
cobject *	m_cobject
	The underlying C cairo surface type that is wrapped by this Surface. More...

Detailed Description

Image surfaces provide the ability to render to memory buffers either allocated by cairo or by the calling code.

The supported image formats are those defined in Format

An ImageSurface is the most generic type of Surface and the only one that is available by default. You can either create an ImageSurface whose data is managed by Cairo, or you can create an ImageSurface with a data buffer that you allocated yourself so that you can have full access to the data.

When you create an ImageSurface with your own data buffer, you are free to examine the results at any point and do whatever you want with it. Note that if you modify anything and later want to continue to draw to the surface with cairo, you must let cairo know via Cairo::Surface::mark_dirty()

Note that like all surfaces, an ImageSurface is a reference-counted object that should be used via Cairo::RefPtr.

Constructor & Destructor Documentation

◆ ImageSurface()

Cairo::ImageSurface::ImageSurface	(	cairo_surface_t *	cobject,
		bool	has_reference = `false`
	)

explicit

Create a C++ wrapper for the C instance.

This C++ instance should then be given to a RefPtr.

Parameters

cobject	The C instance.
has_reference	Whether we already have a reference. Otherwise, the constructor will take an extra reference.

◆ ~ImageSurface()

Cairo::ImageSurface::~ImageSurface ( )

override

Member Function Documentation

◆ create() [1/2]

static RefPtr< ImageSurface > Cairo::ImageSurface::create	(	Format	format,
		int	width,
		int	height
	)

static

Creates an image surface of the specified format and dimensions.

Initially the surface contents are all 0. (Specifically, within each pixel, each color or alpha channel belonging to format will be 0. The contents of bits within a pixel, but not belonging to the given format are undefined).

Parameters

format	format of pixels in the surface to create
width	width of the surface, in pixels
height	height of the surface, in pixels

Returns: a RefPtr to the newly created surface.

Examples: image-surface.cc, toy-text.cc, and user-font.cc.

◆ create() [2/2]

static RefPtr< ImageSurface > Cairo::ImageSurface::create	(	unsigned char *	data,
		Format	format,
		int	width,
		int	height,
		int	stride
	)

static

Creates an image surface for the provided pixel data.

The output buffer must be kept around until the surface is destroyed or finish() is called on the surface. The initial contents of buffer will be used as the initial image contents; you must explicitly clear the buffer, using, for example, Context::rectangle() and Context::fill() if you want it cleared.

Note that the stride may be larger than width * bytes_per_pixel to provide proper alignment for each pixel and row. This alignment is required to allow high-performance rendering within cairo. The correct way to obtain a legal stride value is to call format_stride_for_width() with the desired format and maximum image width value, and the use the resulting stride value to allocate the data and to create the image surface. See format_stride_for_width() for example code.

Parameters

data	a pointer to a buffer supplied by the application in which to write contents. This pointer must be suitably aligned for any kind of variable, (for example, a pointer returned by malloc).
format	the format of pixels in the buffer
width	the width of the image to be stored in the buffer
height	the height of the image to be stored in the buffer
stride	the number of bytes between the start of rows in the buffer as allocated. This value should always be computed by format_stride_for_width() before allocating the data buffer.

Returns: a RefPtr to the newly created surface.

◆ create_from_png()

static RefPtr< ImageSurface > Cairo::ImageSurface::create_from_png ( std::string filename )

static

Creates a new image surface and initializes the contents to the given PNG file.

Note: For this function to be available, cairo must have been compiled with PNG support.

Parameters

filename name of PNG file to load

Returns: a RefPtr to the new cairo_surface_t initialized with the contents of the PNG image file.

◆ create_from_png_stream()

static RefPtr< ImageSurface > Cairo::ImageSurface::create_from_png_stream ( const SlotReadFunc & read_func )

static

Creates a new image surface from PNG data read incrementally via the read_func function.

Note: For this function to be available, cairo must have been compiled with PNG support.

Parameters

read_func function called to read the data of the file

Returns: a RefPtr to the new cairo_surface_t initialized with the contents of the PNG image file.

◆ format_stride_for_width()

static int Cairo::ImageSurface::format_stride_for_width	(	Format	format,
		int	width
	)

static

This function provides a stride value that will respect all alignment requirements of the accelerated image-rendering code within cairo.

Typical usage will be of the form:

int stride;
unsigned char *data;
Cairo::RefPtr<Cairo::ImageSurface> surface;
 
stride = Cairo::ImageSurface::format_stride_for_width (format, width);
data = malloc (stride * height);
surface = Cairo::ImageSurface::create (data, format, width, height);

Parameters

format	A Format value
width	The desired width of an image surface to be created.

Returns: the appropriate stride to use given the desired format and width, or -1 if either the format is invalid or the width too large.

Since: 1.6

◆ get_data() [1/2]

unsigned char * Cairo::ImageSurface::get_data ( )

Get a pointer to the data of the image surface, for direct inspection or modification.

Return value: a pointer to the image data of this surface or NULL if @surface is not an image surface.

Since: 1.2

◆ get_data() [2/2]

const unsigned char * Cairo::ImageSurface::get_data ( ) const

◆ get_format()

Format Cairo::ImageSurface::get_format ( ) const

Gets the format of the surface.

Since: 1.2

◆ get_height()

int Cairo::ImageSurface::get_height ( ) const

Gets the height of the ImageSurface in pixels.

◆ get_stride()

int Cairo::ImageSurface::get_stride ( ) const

Returns the stride of the image surface in bytes (or 0 if surface is not an image surface).

The stride is the distance in bytes from the beginning of one row of the image data to the beginning of the next row.

Since: 1.2

◆ get_width()

int Cairo::ImageSurface::get_width ( ) const

Gets the width of the ImageSurface in pixels.

The documentation for this class was generated from the following file:

cairomm/surface.h

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ ImageSurface()

◆ ~ImageSurface()

Member Function Documentation

◆ create() [1/2]

◆ create() [2/2]

◆ create_from_png()

◆ create_from_png_stream()

◆ format_stride_for_width()

◆ get_data() [1/2]

◆ get_data() [2/2]

◆ get_format()

◆ get_height()

◆ get_stride()

◆ get_width()