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Cairo: A Vector Graphics Library | ![]() |
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Top | Description |
#define CAIRO_HAS_PNG_FUNCTIONS cairo_surface_t * cairo_image_surface_create_from_png (const char *filename); cairo_status_t (*cairo_read_func_t) (void *closure, unsigned char *data, unsigned int length); cairo_surface_t * cairo_image_surface_create_from_png_stream (cairo_read_func_t read_func, void *closure); cairo_status_t cairo_surface_write_to_png (cairo_surface_t *surface, const char *filename); cairo_status_t (*cairo_write_func_t) (void *closure, unsigned char *data, unsigned int length); cairo_status_t cairo_surface_write_to_png_stream (cairo_surface_t *surface, cairo_write_func_t write_func, void *closure);
The PNG functions allow reading PNG images into image surfaces, and writing any surface to a PNG file.
#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.
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.
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name of PNG file to load |
Returns : |
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
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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.
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the input closure |
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the buffer into which to read the data |
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the amount of data to read |
Returns : |
the status code of the read operation |
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.
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function called to read the data of the file |
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data to pass to read_func .
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Returns : |
a new cairo_surface_t initialized with the contents
of the PNG file or NULL if the data read is not a valid PNG image or
memory could not be allocated for the operation.
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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.
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a cairo_surface_t with pixel contents |
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the name of a file to write to |
Returns : |
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.
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cairo_status_t (*cairo_write_func_t) (void *closure, 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.
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the output closure |
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the buffer containing the data to write |
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the amount of data to write |
Returns : |
the status code of the write operation |
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.
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a cairo_surface_t with pixel contents |
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a cairo_write_func_t |
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closure data for the write function |
Returns : |
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.
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