本文演示使用imlib2函数库实现截屏功能
程序运行后，截屏图像保存为jpeg格式文件到当前目录下，起名为“screen.jpeg”

在Debian 5.02系统下，安装libimlib2-dev软件包
imlib2的API文档在 /usr/share/doc/libimlib2-dev/html/index.html

用cvs获取笔者本机screen项目的源代码如下：

$ cvs co -p screen cvs checkout: Updating screen =================================================================== Checking out screen/Makefile RCS:  /home/c-aries/cvs/screen/Makefile,v VERS: 1.2 *************** CC = gcc CFLAGS = -Wall -Werror -Wcast-align -g LDFLAGS = SCREENOBJECT = screen.o GIBLIBCFLAGS = `giblib-config --cflags` GIBLIBLIBS = `giblib-config --libs` all: screen screen: $(SCREENOBJECT)     $(CC) $(LDFLAGS) $(GIBLIBLIBS) $(SCREENOBJECT) -o $@ screen.o: screen.c screen.h     $(CC) $(CFLAGS) $(GIBLIBCFLAGS) -c $< clean:     rm -f screen *~ *.o a.out clean-media:     rm -f *~ *.jpeg .PHONY: all clean =================================================================== Checking out screen/screen.c RCS:  /home/c-aries/cvs/screen/screen.c,v VERS: 1.2 *************** #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <giblib/giblib.h> #include "screen.h" void screen_init(struct screen *screen) {   screen->display = XOpenDisplay(NULL);   if (!screen->display) {     perror("XOpenDisplay");     exit(EXIT_FAILURE);   }   screen->screen = ScreenOfDisplay(screen->display,                   DefaultScreen(screen->display));   screen->visual = DefaultVisual(screen->display,                 DefaultScreen(screen->display));   screen->colormap = DefaultColormap(screen->display,                 DefaultScreen(screen->display));   screen->root = RootWindow(screen->display,                 DefaultScreen(screen->display));   imlib_context_set_display(screen->display);   imlib_context_set_visual(screen->visual);   imlib_context_set_colormap(screen->colormap); } int main(int argc, char *argv[]) {   struct screen screen;   Imlib_Image image;   screen_init(&screen);   image = gib_imlib_create_image_from_drawable(screen.root,                            0,                            0,                            0,                            screen.screen->width,                            screen.screen->height,                            1);   imlib_context_set_image(image);   imlib_image_set_format("jpeg");   imlib_save_image("screen.jpeg");   imlib_free_image();   exit(EXIT_SUCCESS); } =================================================================== Checking out screen/screen.h RCS:  /home/c-aries/cvs/screen/screen.h,v VERS: 1.1.1.1 *************** #ifndef SCREEN_H #define SCREEN_H #include <X11/Xlib.h> struct screen {   Display *display;   Screen *screen;   Visual *visual;   Colormap colormap;   Window root; }; void screen_init(struct screen *screen); #endif $

该程序参考了scrot项目的源代码和imlib2的编程文档

上周的文章 video4linux2编程实例 使用video4linux2编程接口获得摄像头数据流，再将YUYV数据流转换成RGB数据流。
然后想添加截取图片功能，将摄像头的RGB数据流保存成JPEG图片。
找来平时一直在使用的自由软件scrot，阅读其源代码，即找到将RGB保存成JPEG图片的方法:
“将用于SDL的像素格式RGBA转换成用于imlib2的像素格式ARGB，再用imlib2的imlib_create_image_using_data()函数保存成JPEG图片”
这部分的代码下周再介绍吧：）

实现截取图片功能的期间，学会了截屏功能……
于是顺便把实现截屏的代码贴出来，作为编程实例。

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