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Cairo: A Vector Graphics Library | |
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enum cairo_format_t; cairo_surface_t* cairo_image_surface_create (cairo_format_t format, int width, int height); cairo_surface_t* cairo_image_surface_create_for_data (unsigned char *data, cairo_format_t format, int width, int height, int stride); int cairo_image_surface_get_width (cairo_surface_t *surface); int cairo_image_surface_get_height (cairo_surface_t *surface);
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 cairo_format_t.
typedef enum _cairo_format {
CAIRO_FORMAT_ARGB32,
CAIRO_FORMAT_RGB24,
CAIRO_FORMAT_A8,
CAIRO_FORMAT_A1
} cairo_format_t;
cairo_format_t is used to identify the memory format of image data.
| each pixel is a 32-bit quantity, with alpha in the upper 8 bits, then red, then green, then blue. The 32-bit quantities are stored native-endian. Pre-multiplied alpha is used. (That is, 50% transparent red is 0x80800000, not 0x80ff0000.) | |
| each pixel is a 32-bit quantity, with the upper 8 bits unused. Red, Green, and Blue are stored in the remaining 24 bits in that order. | |
| each pixel is a 8-bit quantity holding an alpha value. | |
| each pixel is a 1-bit quantity holding an alpha value. Pixels are packed together into 32-bit quantities. The ordering of the bits matches the endianess of the platform. On a big-endian machine, the first pixel is in the uppermost bit, on a little-endian machine the first pixel is in the least-significant bit. |
cairo_surface_t* cairo_image_surface_create (cairo_format_t format, int width, int height);
Creates an image surface of the specified format and
dimensions. The initial contents of the surface is undefined; you
must explicitely clear the buffer, using, for example,
cairo_rectangle() and cairo_fill() if you want it cleared.
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format of pixels in the surface to create |
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width of the surface, in pixels |
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height of the surface, in pixels |
Returns : |
a pointer to the newly created surface. The caller
owns the surface and should call cairo_surface_destroy when done
with it.
This function always returns a valid pointer, but it will return a
pointer to a "nil" surface if an error such as out of memory
occurs. You can use cairo_surface_status() to check for this.
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cairo_surface_t* cairo_image_surface_create_for_data (unsigned char *data, cairo_format_t format, int width, int height, int stride);
Creates an image surface for the provided pixel data. The output
buffer must be kept around until the cairo_surface_t is destroyed
or cairo_surface_finish() is called on the surface. The initial
contents of buffer will be used as the inital image contents; you
must explicitely clear the buffer, using, for example,
cairo_rectangle() and cairo_fill() if you want it cleared.
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a pointer to a buffer supplied by the application in which to write contents. |
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the format of pixels in the buffer |
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the width of the image to be stored in the buffer |
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the height of the image to be stored in the buffer |
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the number of bytes between the start of rows
in the buffer. Having this be specified separate from width
allows for padding at the end of rows, or for writing
to a subportion of a larger image.
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Returns : |
a pointer to the newly created surface. The caller
owns the surface and should call cairo_surface_destroy when done
with it.
This function always returns a valid pointer, but it will return a
pointer to a "nil" surface if an error such as out of memory
occurs. You can use cairo_surface_status() to check for this.
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int cairo_image_surface_get_width (cairo_surface_t *surface);
Get the width of the image surface in pixels.
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a cairo_image_surface_t |
Returns : |
the width of the surface in pixels. |
int cairo_image_surface_get_height (cairo_surface_t *surface);
Get the height of the image surface in pixels.
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a cairo_image_surface_t |
Returns : |
the height of the surface in pixels. |