NAME
XInitImage, XCreateImage, XGetPixel, XPutPixel, XSubImage, XAddPixel,
XDestroyImage - image utilities
SYNTAX
Status
XInitImage(XImage * image);
XImage
*XCreateImage(Display * display, Visual *visual, unsigned int
depth, int format, int offset, char * data,
unsigned int width, unsigned int height, int bitmap_pad,
int bytes_per_line);
unsigned long
XGetPixel(XImage * ximage, int x, int y);
int
XPutPixel(XImage * ximage, int x, int y, unsigned long
pixel);
XImage
*XSubImage(XImage * ximage, int x, int y, unsigned int
subimage_width, unsigned int subimage_height);
int
XAddPixel(XImage * ximage, long value);
int
XDestroyImage(XImage * ximage);
ARGUMENTS
- bitmap_pad
- Specifies the quantum of a scanline (8, 16, or 32). In
other words, the start of one scanline is separated in client memory from
the start of the next scanline by an integer multiple of this many
bits.
- bytes_per_line
- Specifies the number of bytes in the client image between
the start of one scanline and the start of the next.
- data
- Specifies the image data.
- depth
- Specifies the depth of the image.
- display
- Specifies the connection to the X server.
- format
- Specifies the format for the image. You can pass
XYBitmap, XYPixmap, or ZPixmap.
- height
- Specifies the height of the image, in pixels.
- offset
- Specifies the number of pixels to ignore at the beginning
of the scanline.
- pixel
- Specifies the new pixel value.
- subimage_height
- Specifies the height of the new subimage, in pixels.
- subimage_width
- Specifies the width of the new subimage, in pixels.
- value
- Specifies the constant value that is to be added.
- visual
- Specifies the Visual structure.
- width
- Specifies the width of the image, in pixels.
- ximage
- Specifies the image.
- x
-
- y
- Specify the x and y coordinates.
DESCRIPTION
The
XInitImage function initializes the internal image manipulation
routines of an image structure, based on the values of the various structure
members. All fields other than the manipulation routines must already be
initialized. If the bytes_per_line member is zero,
XInitImage will
assume the image data is contiguous in memory and set the bytes_per_line
member to an appropriate value based on the other members; otherwise, the
value of bytes_per_line is not changed. All of the manipulation routines are
initialized to functions that other Xlib image manipulation functions need to
operate on the type of image specified by the rest of the structure.
This function must be called for any image constructed by the client before
passing it to any other Xlib function. Image structures created or returned by
Xlib do not need to be initialized in this fashion.
This function returns a nonzero status if initialization of the structure is
successful. It returns zero if it detected some error or inconsistency in the
structure, in which case the image is not changed.
The
XCreateImage function allocates the memory needed for an
XImage structure for the specified display but does not allocate space
for the image itself. Rather, it initializes the structure byte-order,
bit-order, and bitmap-unit values from the display and returns a pointer to
the
XImage structure. The red, green, and blue mask values are defined
for Z format images only and are derived from the
Visual structure
passed in. Other values also are passed in. The offset permits the rapid
displaying of the image without requiring each scanline to be shifted into
position. If you pass a zero value in bytes_per_line, Xlib assumes that the
scanlines are contiguous in memory and calculates the value of bytes_per_line
itself.
Note that when the image is created using
XCreateImage,
XGetImage,
or
XSubImage, the destroy procedure that the
XDestroyImage
function calls frees both the image structure and the data pointed to by the
image structure.
The basic functions used to get a pixel, set a pixel, create a subimage, and add
a constant value to an image are defined in the image object. The functions in
this section are really macro invocations of the functions in the image object
and are defined in <
X11/Xutil.h>.
The
XGetPixel function returns the specified pixel from the named image.
The pixel value is returned in normalized format (that is, the least
significant byte of the long is the least significant byte of the pixel). The
image must contain the x and y coordinates.
The
XPutPixel function overwrites the pixel in the named image with the
specified pixel value. The input pixel value must be in normalized format
(that is, the least significant byte of the long is the least significant byte
of the pixel). The image must contain the x and y coordinates.
The
XSubImage function creates a new image that is a subsection of an
existing one. It allocates the memory necessary for the new
XImage
structure and returns a pointer to the new image. The data is copied from the
source image, and the image must contain the rectangle defined by x, y,
subimage_width, and subimage_height.
The
XAddPixel function adds a constant value to every pixel in an image.
It is useful when you have a base pixel value from allocating color resources
and need to manipulate the image to that form.
The
XDestroyImage function deallocates the memory associated with the
XImage structure.
SEE ALSO
XPutImage(3)
Xlib - C Language X Interface