XCreateImage(3X11)
NAME
XInitImage, XCreateImage, XGetPixel, XPutPixel, XSubImage,
XAddPixel, XDestroyImage - image utilities
SYNTAX
Status XInitImage(image)
XImage *image;
XImage *XCreateImage(display, visual, depth, format, off-
set, data, width, height, bitmap_pad,
bytes_per_line)
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, x, y)
XImage *ximage;
int x;
int y;
XPutPixel(ximage, x, y, pixel)
XImage *ximage;
int x;
int y;
unsigned long pixel;
XImage *XSubImage(ximage, x, y, subimage_width,
subimage_height)
XImage *ximage;
int x;
int y;
unsigned int subimage_width;
unsigned int subimage_height;
XAddPixel(ximage, value)
XImage *ximage;
long value;
XDestroyImage(ximage)
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 pix-
els.
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 initial-
ized. 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 ini-
tialized 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 initial-
izes the structure byte-order, bit-order, and bitmap-unit
values from the display and returns a pointer to the XIm-
age 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 posi-
tion. 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 struc-
ture and the data pointed to by the image structure.
The basic functions used to get a pixel, set a pixel, cre-
ate a subimage, and add a constant value to an image are
defined in the image object. The functions in this sec-
tion 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 normal-
ized 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 coordi-
nates.
The XSubImage function creates a new image that is a sub-
section of an existing one. It allocates the memory nec-
essary 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 associ-
ated with the XImage structure.
SEE ALSO
XPutImage(3X11)
Xlib - C Language X Interface