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<HTML><HEAD><TITLE>Xlib Programming Manual: Image Format Functions and Macros</TITLE></HEAD><BODY><H1 ALIGN=center>2.2.2. Image Format Functions and Macros</H1>Applications are required to present data to the X serverin a format that the server demands.To help simplify applications,most of the work required to convert the data is provided by Xlib(see "<A HREF="../graphics/images.html">Transferring Images between Client and Server</A>" and "<A HREF="../utilities/manipulating-images.html">Manipulating Images</A>").<A NAME="XPixmapFormatValues"></A><P>The<U>XPixmapFormatValues</U>structure provides an interface to the pixmap format informationthat is returned at the time of a connection setup.It contains:<P><PRE><CODE>typedef struct { int depth; int bits_per_pixel; int scanline_pad;} XPixmapFormatValues;</CODE></PRE><P><A NAME="XListPixmapFormats"></A><H3>XListPixmapFormats</H3>To obtain the pixmap format information for a given display, use<B>XListPixmapFormats()</B> .<!.IN "XListPixmapFormats" "" "@DEF@"><CODE><PRE><A HREF="#XPixmapFormatValues">XPixmapFormatValues</A> *XListPixmapFormats(<B>display</B>, <B>count_return</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>; int *<B>count_return</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>count_return</B><TD> Returns the number of pixmap formats that are supported by the display.</TABLE><P>The<B>XListPixmapFormats()</B>function returns an array of<A HREF="#XPixmapFormatValues">XPixmapFormatValues</A>structures that describe the types of Z format images supportedby the specified display.If insufficient memory is available,<B>XListPixmapFormats</B>returns NULL.To free the allocated storage for the<A HREF="#XPixmapFormatValues">XPixmapFormatValues</A>structures, use<B><A HREF="XFree.html">XFree()</A></B>.<P> The following lists the C language macros,their corresponding function equivalents that are for other language bindings,and what data they both return for the specified server and screen.These are often used by toolkits as well as by simple applications.<P><A NAME="ImageByteOrder"></A><H3>ImageByteOrder</H3><CODE><PRE>ImageByteOrder(<B>display</B>)int XImageByteOrder(<B>display</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.</TABLE><P><!.IN "ImageByteOrder" "" "@DEF@"><!.IN "XImageByteOrder" "" "@DEF@">Both specify the required byte order for images for each scanline unit in XY format (bitmap) or for each pixel value in Z format.The macro or function can return either<B>LSBFirst</B> or <B>MSBFirst</B> .<P><A NAME="BitmapUnit"></A><H3>BitmapUnit</H3><CODE><PRE>BitmapUnit(<B>display</B>)int XBitmapUnit(<B>display</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.</TABLE><P><!.IN "BitmapUnit" "" "@DEF@"><!.IN "XBitmapUnit" "" "@DEF@">Both return the size of a bitmap's scanline unit in bits.The scanline is calculated in multiples of this value.<P><A NAME="BitmapBitOrder"></A><H3>BitmapBitOrder</H3><CODE><PRE>BitmapBitOrder(<B>display</B>)int XBitmapBitOrder(<B>display</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.</TABLE><P><!.IN "BitmapBitOrder" "" "@DEF@"><!.IN "XBitmapBitOrder" "" "@DEF@">Within each bitmap unit, the left-most bit in the bitmap as displayedon the screen is either the least-significant or most-significant bit in theunit.This macro or function can return <B>LSBFirst</B>or <B>MSBFirst</B>.<A NAME="BitmapPad"></A><H3>BitmapPad</H3><CODE><PRE>BitmapPad(<B>display</B>)int XBitmapPad(<B>display</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.</TABLE><P><!.IN "BitmapPad" "" "@DEF@"><!.IN "XBitmapPad" "" "@DEF@">Each scanline must be padded to a multiple of bits returnedby this macro or function.<A NAME="DisplayHeight"></A><H3>DisplayHeight</H3><CODE><PRE>DisplayHeight(<B>display</B>, <B>screen_number</B>)int XDisplayHeight(<B>display</B>, <B>screen_number</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>; int <B>screen_number</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>screen_number</B><TD> Specifies the appropriate screen number on the host server.</TABLE><!.IN "DisplayHeight" "" "@DEF@"><!.IN "XDisplayHeight" "" "@DEF@">Both return an integer that describes the height of the screenin pixels.<A NAME="DisplayHeightMM"></A><H3>DisplayHeightMM</H3><CODE><PRE>DisplayHeightMM(<B>display</B>, <B>screen_number</B>)int XDisplayHeightMM(<B>display</B>, <B>screen_number</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>; int <B>screen_number</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>screen_number</B><TD> Specifies the appropriate screen number on the host server.</TABLE><P><!.IN "DisplayHeightMM" "" "@DEF@"><!.IN "XDisplayHeightMM" "" "@DEF@">Both return the height of the specified screen in millimeters.<A NAME="DisplayWidth"></A><H3>DisplayWidth</H3><CODE><PRE>DisplayWidth(<B>display</B>, <B>screen_number</B>)int XDisplayWidth(<B>display</B>, <B>screen_number</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>; int <B>screen_number</B>;</PRE></CODE><TABLE><P><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>screen_number</B><TD> Specifies the appropriate screen number on the host server.</TABLE><P><!.IN "DisplayWidth" "" "@DEF@"><!.IN "XDisplayWidth" "" "@DEF@">Both return the width of the screen in pixels.<A NAME="DisplayWidthMM"></A><H3>DisplayWidthMM</H3><CODE><PRE>DisplayWidthMM(<B>display</B>, <B>screen_number</B>)int XDisplayWidthMM(<B>display</B>, <B>screen_number</B>) <A HREF="opening.html#Display">Display</A> *<B>display</B>; int <B>screen_number</B>;</PRE></CODE><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>screen_number</B><TD> Specifies the appropriate screen number on the host server.</TABLE><P><!.IN "DisplayWidthMM" "" "@DEF@"><!.IN "XDisplayWidthMM" "" "@DEF@">Both return the width of the specified screen in millimeters.<H5 ALIGN=right><I>Next: <A HREF="screen-information.html">Screen Information Macros</A></I></H5><HR><ADDRESS><A HREF="http://tronche.com/">Christophe Tronche</A>, <A HREF="mailto:ch.tronche@computer.org">ch.tronche@computer.org</A></ADDRESS></BODY></HTML>⌨️ 快捷键说明
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