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

#include

#include

#include

#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

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。