XGetSubImage − copy a rectangle in drawable to a location within the pre-existing image.
Synopsis
XImage *XGetSubImage(display, drawable, x, y, width, height,
plane_mask, format, dest_image, dest_x, dest_y)
Display *display;
Drawable drawable;
int x, y;
unsigned int width, height;
unsigned long plane_mask;
int format;
XImage *dest_image;
int dest_x, dest_y;
Arguments
displaySpecifies a connection to an X server; returned from XOpenDisplay().
drawableSpecifies the drawable from which the rectangle is to be copied.
x
ySpecify the x and y coordinates of the upper-left corner of the rectangle, relative to the origin of the drawable.
width
heightSpecify the width and height in pixels of the subimage taken.
plane_mask
Specifies which planes of the drawable are transferred to the image.
formatSpecifies the format for the image. Either XYPixmap or ZPixmap.
dest_image
Specifies the the destination image.
dest_x
dest_ySpecify the x and y coordinates of the destination rectangle’s upper left corner, relative to the image’s origin.
Description
XGetSubImage() updates the dest_image with the specified subimage in the same manner as XGetImage(), except that it does not create the image or necessarily fill the entire image. If format is XYPixmap, the function transmits only the bit planes you specify in plane_mask. If format is ZPixmap, the function transmits as zero the bits in all planes not specified in plane_mask. The function performs no range checking on the values in plane_mask and ignores extraneous bits. The depth of the destination XImage structure must be the same as that of the drawable. Otherwise, a BadMatch error is generated. If the specified subimage does not fit at the specified location on the destination image, the right and bottom edges are clipped. If the drawable is a window, the window must be mapped or held in backing store, and it must be the case that, if there were no inferiors or overlapping windows, the specified rectangle of the window would be fully visible on the screen. Otherwise, a BadMatch error is generated. If the window has a backing store, the backing store contents are returned for regions of the window that are obscured by noninferior windows. Otherwise, the return contents of such obscured regions are undefined. Also undefined are the returned contents of visible regions of inferiors of different depth than the specified window. XSubImage() extracts a subimage from an image, instead of from a drawable like XGetSubImage(). If a problem occurs, XGetSubImage() returns NULL. For more information on images, see Volume One, Chapter 6, Drawing Graphics and Text.
Errors
BadDrawable
BadGC
BadMatchDepth of dest_image is not the same as depth of drawable.
BadValue
See Also
ImageByteOrder(), XAddPixel(), XCreateImage(), XDestroyImage(), XGetImage(), XGetPixel(), XPutImage(), XPutPixel(), XSubImage().
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