如何以Java实现网页截图技术

2025-03-04 10:40:12
推荐回答(1个)
回答1:

事实上,如果您想以Java实现网页截图,也就是“输入一段网址,几秒钟过后就能截取一张网页缩略图”的效果。那么,您至少有3种方式可以选择。

1、最直接的方式——使用Robot

方法详解:该方法利用Robat提供的强大桌面操作能力,硬性调用浏览器打开指定网页,并将网页信息保存到本地。

优势:简单易用,不需要任何第三方插件。

缺点:不能同时处理大量数据,技术含量过低,属于应急型技巧。

实现方法:使用如下代码即可。

[java] view plaincopy
public static void main(String[] args) throws MalformedURLException,
IOException, URISyntaxException, AWTException {
//此方法仅适用于JdK1.6及以上版本
Desktop.getDesktop().browse(
new URL("http://google.com/intl/en/").toURI());
Robot robot = new Robot();
robot.delay(10000);
Dimension d = new Dimension(Toolkit.getDefaultToolkit().getScreenSize());
int width = (int) d.getWidth();
int height = (int) d.getHeight();
//最大化浏览器
robot.keyRelease(KeyEvent.VK_F11);
robot.delay(2000);
Image image = robot.createScreenCapture(new Rectangle(0, 0, width,
height));
BufferedImage bi = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
Graphics g = bi.createGraphics();
g.drawImage(image, 0, 0, width, height, null);
//保存图片
ImageIO.write(bi, "jpg", new File("google.jpg"));
}

2、最常规的方式——利用JNI,调用第三方C/C++组件

方法详解:目前来讲,Java领域对于网页截图组件的开发明显不足(商机?),当您需要完成此种操作时,算得上碰到了Java的软肋。但是,众所周知Java也拥有强大的JNI能力,可以轻易将C/C++开发的同类组件引为己用。不懂可以扣五七八零二四一四四
优势:实现简单,只需要封装对应的DLL文件,就可以让Java实现同类功能。

劣势:同其他JNI实现一样,在跨平台时存在隐患,而且您的程序将不再属于纯Java应用。

实现方法:可参见此用例,具体封装何种C/C++组件请自行选择。

PS:示例来源于ACA HTML to Image Converter项目(http://www.acasystems.com/en/web-thumb-activex/faq-convert-html-to-image-in-java.htm ),这是一个收费的HTML转Image第三方组件,但封装方式在Java中大同小异。

引用JNI封装:

[java] view plaincopy
import sun.awt.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.awt.peer.*;
public class Snap
{
static
{
System.loadLibrary("Snap");
}
public static void main( String[] argv )
{
Snap t_xSnap = new Snap();
t_xSnap.Start("http://www.google.com", "snapshot-google.png");
}
public native void Start(String pi_strURL, String pi_strImageName);
}

CPP部分的实现:

[java] view plaincopy
#include
#include
#include "snap.h"
#pragma comment(lib,"atl.lib")
#import "./../../acawebthumb.dll" no_namespace
JNIEXPORT void JNICALL Java_Snap_Start(JNIEnv *pEnv, jobject, jstring pi_strUrl, jstring pi_strFileName)
{
CoInitialize(0);
_bstr_t t_strUrl = pEnv->GetStringUTFChars(pi_strUrl, 0);
_bstr_t t_strFileName = pEnv->GetStringUTFChars(pi_strFileName, 0);
IThumbMakerPtr HTML_Converter = NULL;
HRESULT hr = HTML_Converter.CreateInstance(L"ACAWebThumb.ThumbMaker");
if (SUCCEEDED(hr))
{
HTML_Converter->SetURL(t_strUrl);
if ( 0 == HTML_Converter->StartSnap() )
HTML_Converter->SaveImage(t_strFileName);
}
if (HTML_Converter)
HTML_Converter.Release();
CoUninitialize();
}

以该组件图像化yahoo界面的效果图:

3、最扎实的方法——自行解析HTML标记,并将其图像化

方法详解:众所周知,HTML之所以在浏览器中以具体的网页格式出现,并非服务器端传了一整个应用到客户端,而是源自于浏览器对于客户端自行解析的结果。因此,只要我们将对应的解析一一实现,那么将网页图形化,就将不是什么难事。

优势:纯Java实现,一劳永逸,一旦开发完成则永远通用,而且有一定的商用价值。

劣势:开发费时,且需要针对不同语法做精确分析,才能保证输出的基本正确。尤其在涉及到JavaScript解析时,难度将尤其增大。

实现方法:目前尚无具体案例可供参考。但是,由于Java有jdic之类的浏览器项目存在(https://jdic.dev.java.net/),而Java图形界面又属绘制生成。从理论上说,我们可以将所有具备Graphics的组件图形化保存。

而如果自行解析,那么您需要建立HTML解析器(或使用第三方的,万幸Java在这方面的组件很多),了解Java2D机制,了解何时该使用drawString绘制文字,何时又该使用drawImage插入图片等等。
谢谢采纳!

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