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Cairo: A Vector Graphics Library | ![]() |
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enum cairo_format_t; int cairo_format_stride_for_width (cairo_format_t format, int width); 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); unsigned char* cairo_image_surface_get_data (cairo_surface_t *surface); cairo_format_t cairo_image_surface_get_format (cairo_surface_t *surface); int cairo_image_surface_get_width (cairo_surface_t *surface); int cairo_image_surface_get_height (cairo_surface_t *surface); int cairo_image_surface_get_stride (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 /* The value of 4 is reserved by a deprecated enum value. * The next format added must have an explicit value of 5. CAIRO_FORMAT_RGB16_565 = 4, */ } cairo_format_t;
cairo_format_t is used to identify the memory format of image data.
New entries may be added in future versions.
int cairo_format_stride_for_width (cairo_format_t format, int width);
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_surface_t *surface; stride = cairo_format_stride_for_width (format, width); data = malloc (stride * height); surface = cairo_image_surface_create_for_data (data, format, width, height);
format : | A cairo_format_t 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
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. 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).
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 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. |
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 initial image contents; you must explicitly clear the buffer, using, for example, cairo_rectangle() and cairo_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 cairo_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 cairo_format_stride_for_width() for example code.
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 cairo_format_stride_for_width() before allocating the data buffer. |
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 in the case of an error such as out of memory or an invalid stride value. In case of invalid stride value the error status of the returned surface will be CAIRO_STATUS_INVALID_STRIDE. You can use cairo_surface_status() to check for this. See cairo_surface_set_user_data() for a means of attaching a destroy-notification fallback to the surface if necessary. |
unsigned char* cairo_image_surface_get_data (cairo_surface_t *surface);
Get a pointer to the data of the image surface, for direct inspection or modification.
surface : | a cairo_image_surface_t |
Returns : | a pointer to the image data of this surface or NULL if surface is not an image surface. |
Since 1.2
cairo_format_t cairo_image_surface_get_format (cairo_surface_t *surface);
Get the format of the surface.
surface : | a cairo_image_surface_t |
Returns : | the format of the surface |
Since 1.2
int cairo_image_surface_get_width (cairo_surface_t *surface);
Get the width of the image surface in pixels.
surface : | 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.
surface : | a cairo_image_surface_t |
Returns : | the height of the surface in pixels. |
int cairo_image_surface_get_stride (cairo_surface_t *surface);
Get the stride of the image surface in bytes
surface : | a cairo_image_surface_t |
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