📄 manipulating-images.html
字号:
<HTML><HEAD><TITLE>Xlib Programming Manual: Manipulating Images</TITLE></HEAD><BODY><H1 ALIGN=center>16.8 Manipulating Images</H1>Xlib provides several functions that perform basic operations on images.All operations on images are defined using an <A HREF="../graphics/images.html#XImage">XImage</A> structure, as defined in<B><TT>X11/Xlib.h.</TT></B>Because the number of different types of image formats can be very large,this hides details of image storage properly from applications.<P>This section describes the functions for generic operations on images.Manufacturers can provide very fast implementations of these for theformats frequently encountered on their hardware.These functions are neither sufficient nor desirable to use for general imageprocessing.Rather, they are here to provide minimal functions on screen formatimages.The basic operations for getting and putting images are<B><A HREF="../graphics/XGetImage.html">XGetImage()</A></B>and <B><A HREF="../graphics/XPutImage.html">XPutImage()</A></B>.<P>Note that no functions have been defined, as yet, to read and write images to and from disk files.<P>The<A HREF="../graphics/images.html#XImage">XImage</A> structure describes an image as it exists in the client's memory. The user can request that some of the members such as height, width, and xoffset be changed when the image is sent to the server.Note that bytes_per_line in concert with offset can be used toextract a subset of the image.Other members (for example, byte order, bitmap_unit, and so forth)are characteristics of both the image and the server. If these membersdiffer between the image and the server, <B><A HREF="../graphics/XPutImage.html">XPutImage()</A></B>makes the appropriate conversions.The first byte of the first line ofplane n must be located at the address (data + (n * height * bytes_per_line)).For a description of the <A HREF="../graphics/images.html#XImage">XImage</A> structure,see "<A HREF="../graphics/images.html">Transferring Images between Client and Server</A>".<P>To allocate an <A HREF="../graphics/images.html#XImage">XImage</A> structure and initialize it with image format values from a display, use<B><A HREF="XCreateImage.html">XCreateImage()</A></B>.<P>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 functionsin the image object and are defined in<B><TT>X11/Xutil.h.</TT></B><P>To obtain a pixel value in an image, use<B><A HREF="XGetPixel.html">XGetPixel()</A></B>.<P>To set a pixel value in an image, use<B><A HREF="XPutPixel.html">XPutPixel()</A></B>.<P>To create a subimage, use<B><A HREF="XSubImage.html">XSubImage()</A></B>.<P>To increment each pixel in an image by a constant value, use<B><A HREF="XAddPixel.html">XAddPixel()</A></B>.<P>To deallocate the memory allocated in a previous call to<B><A HREF="XCreateImage.html">XCreateImage()</A></B>,use<B><A HREF="XDestroyImage.html">XDestroyImage()</A></B>.<H5 ALIGN=right><I>Next: <A HREF="manipulating-bitmaps.html">Manipulating Bitmaps</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
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -