XCreateImage(3) XLIB FUNCTIONS XCreateImage(3)
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 subim-
age_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 mem-
ory from the start of the next scanline by an integer multi-
ple 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 spec-
ified 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 struc-
ture is successful. It returns zero if it detected some error or in-
consistency 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-or-
der, 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 subim-
age, and add a constant value to an image are defined in the image ob-
ject. 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 im-
age. 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 co-
ordinates.
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 im-
age. 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
X Version 11 libX11 1.8.4 XCreateImage(3)
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