]> PNG Support 3 CAIRO Library PNG Support Reading and writing PNG images cairo_surface_t * cairo_image_surface_create_from_png () cairo_status_t (*cairo_read_func_t) () cairo_surface_t * cairo_image_surface_create_from_png_stream () cairo_status_t cairo_surface_write_to_png () cairo_status_t (*cairo_write_func_t) () cairo_status_t cairo_surface_write_to_png_stream () #defineCAIRO_HAS_PNG_FUNCTIONS The PNG functions allow reading PNG images into image surfaces, and writing any surface to a PNG file. It is a toy API. It only offers very simple support for reading and writing PNG files, which is sufficient for testing and demonstration purposes. Applications which need more control over the generated PNG file should access the pixel data directly, using cairo_image_surface_get_data() or a backend-specific access function, and process it with another library, e.g. gdk-pixbuf or libpng. cairo_image_surface_create_from_png cairo_surface_t * cairo_image_surface_create_from_png (const char *filename); Creates a new image surface and initializes the contents to the given PNG file. filename name of PNG file to load. On Windows this filename is encoded in UTF-8. a new cairo_surface_t initialized with the contents of the PNG file, or a "nil" surface if any error occurred. A nil surface can be checked for with cairo_surface_status(surface) which may return one of the following values: CAIRO_STATUS_NO_MEMORY CAIRO_STATUS_FILE_NOT_FOUND CAIRO_STATUS_READ_ERROR CAIRO_STATUS_PNG_ERROR Alternatively, you can allow errors to propagate through the drawing operations and check the status on the context upon completion using cairo_status(). Since: 1.0 cairo_read_func_t cairo_status_t (*cairo_read_func_t) (void *closure, unsigned char *data, unsigned int length); cairo_read_func_t is the type of function which is called when a backend needs to read data from an input stream. It is passed the closure which was specified by the user at the time the read function was registered, the buffer to read the data into and the length of the data in bytes. The read function should return CAIRO_STATUS_SUCCESS if all the data was successfully read, CAIRO_STATUS_READ_ERROR otherwise. closure the input closure data the buffer into which to read the data length the amount of data to read the status code of the read operation Since: 1.0 cairo_image_surface_create_from_png_stream cairo_surface_t * cairo_image_surface_create_from_png_stream (cairo_read_func_t read_func, void *closure); Creates a new image surface from PNG data read incrementally via the read_func function. read_func function called to read the data of the file closure data to pass to read_func . a new cairo_surface_t initialized with the contents of the PNG file or a "nil" surface if the data read is not a valid PNG image or memory could not be allocated for the operation. A nil surface can be checked for with cairo_surface_status(surface) which may return one of the following values: CAIRO_STATUS_NO_MEMORY CAIRO_STATUS_READ_ERROR CAIRO_STATUS_PNG_ERROR Alternatively, you can allow errors to propagate through the drawing operations and check the status on the context upon completion using cairo_status(). Since: 1.0 cairo_surface_write_to_png cairo_status_t cairo_surface_write_to_png (cairo_surface_t *surface, const char *filename); Writes the contents of surface to a new file filename as a PNG image. surface a cairo_surface_t with pixel contents filename the name of a file to write to; on Windows this filename is encoded in UTF-8. CAIRO_STATUS_SUCCESS if the PNG file was written successfully. Otherwise, CAIRO_STATUS_NO_MEMORY if memory could not be allocated for the operation or CAIRO_STATUS_SURFACE_TYPE_MISMATCH if the surface does not have pixel contents, or CAIRO_STATUS_WRITE_ERROR if an I/O error occurs while attempting to write the file, or CAIRO_STATUS_PNG_ERROR if libpng returned an error. Since: 1.0 cairo_write_func_t cairo_status_t (*cairo_write_func_t) (void *closure, const unsigned char *data, unsigned int length); cairo_write_func_t is the type of function which is called when a backend needs to write data to an output stream. It is passed the closure which was specified by the user at the time the write function was registered, the data to write and the length of the data in bytes. The write function should return CAIRO_STATUS_SUCCESS if all the data was successfully written, CAIRO_STATUS_WRITE_ERROR otherwise. closure the output closure data the buffer containing the data to write length the amount of data to write the status code of the write operation Since: 1.0 cairo_surface_write_to_png_stream cairo_status_t cairo_surface_write_to_png_stream (cairo_surface_t *surface, cairo_write_func_t write_func, void *closure); Writes the image surface to the write function. surface a cairo_surface_t with pixel contents write_func a cairo_write_func_t closure closure data for the write function CAIRO_STATUS_SUCCESS if the PNG file was written successfully. Otherwise, CAIRO_STATUS_NO_MEMORY is returned if memory could not be allocated for the operation, CAIRO_STATUS_SURFACE_TYPE_MISMATCH if the surface does not have pixel contents, or CAIRO_STATUS_PNG_ERROR if libpng returned an error. Since: 1.0 CAIRO_HAS_PNG_FUNCTIONS #define CAIRO_HAS_PNG_FUNCTIONS 1 Defined if the PNG functions are available. This macro can be used to conditionally compile code using the cairo PNG functions. Since: 1.0 cairo_surface_t