XCreateImage(3X11) XLIB FUNCTIONS XCreateImage(3X11)
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.
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XCreateImage(3X11) XLIB FUNCTIONS XCreateImage(3X11)
subimage_height
Specifies the height of the new subimage, in pix-
els.
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 mani-
pulation 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 struc-
ture. 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 per-
mits the rapid displaying of the image without requiring
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XCreateImage(3X11) XLIB FUNCTIONS XCreateImage(3X11)
each scanline to be shifted into position. If you pass a
zero value in bytes_per_line, Xlib assumes that the scan-
lines 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 for-
mat (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 subsec-
tion 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(3X11)
Xlib - C Language X Interface
XFree86 Version 4.5.0 3