根据html来生成图片很多时候都会被用到，最常见的就是网页截图。通过html模板技术，可以让用户自定义一段html，然后为用户实时生成图片。
以下就是使用java 2D实现的html生成图片的方法，需要用到两个开源的jar包。core-renderer.jar，jtidy-r938.jar，这两个jar包是用来渲染html页面的，但是不支持执行javasrcipt。另外还需要xmlgraphics-commons-1.4.jar，这是用来生成PNG图片的。
为了支持中文显示自动换行，需要修改org.xhtmlrenderer.layout.Breaker类。
因为xhtmlrenderer是外国人写的，默认是根据空格来决定是否可以换行的，但是中文语句都是没有空格的，修改后的行为就像样式word-break:break-all。core-renderer-repack.jar是我重新打的包，包含了Breaker.java的源代码。
以下是代码：
public class ImageGenerator {
private float jpgQuality = 0.9F;
private boolean useHighScaleQuality = true;
private ImageFormat imageFormat = ImageFormat.JPG;
private ChineseFontResolver fontResolver;
private static final Logger logger = Logger.getLogger(ImageGenerator.class);
public void init() {
XRLog.init("init log...");
initTidy();
}
private Tidy tidy = null;
private static HashMap RENDER_HINT = new HashMap();
static{
RENDER_HINT.put(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
RENDER_HINT.put(RenderingHints.KEY_ANTIALIASING,RenderingHints. VALUE_ANTIALIAS_ON);
RENDER_HINT.put(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
RENDER_HINT.put(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
RENDER_HINT.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
RENDER_HINT.put(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
RENDER_HINT.put(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
}
private static HashMap RENDER_SCALE_HINT = new HashMap();
static{
RENDER_SCALE_HINT.put(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
}
private void initTidy() {
tidy = new Tidy();
tidy.setQuiet(true);
tidy.setXHTML(true);
tidy.setHideComments(true);
tidy.setInputEncoding("UTF-8");
tidy.setOutputEncoding("UTF-8");
tidy.setShowErrors(0);
tidy.setShowWarnings(false);
}
/**
* 按默认配置生成图片
* @param input
* @param width
* @param height
* @return
*/
public ByteArrayOutputStream html2Image(InputStream input, int width, int height) {
ByteArrayOutputStream output = null;
try {
BufferedImage image = generateImage(input, width, height, RENDER_HINT);
output = generateOutput(image);
} catch (Exception e) {
logger.error("generate image fail.");
e.printStackTrace();
}
return output;
}
/**
* 生成图片并缩放
* @param input
* @param width
* @param height
* @param scaledWidth
* @param scaledHeight
* @return
*/
public ByteArrayOutputStream html2Image(InputStream input, int width, int height, int scaledWidth, int scaledHeight) {
ByteArrayOutputStream output = null;
try {
HashMap hints = scaledWidth < width ? RENDER_SCALE_HINT : RENDER_HINT;
BufferedImage image = generateImage(input, width, height, hints);
BufferedImage scaled = scale(image, width, height, scaledWidth, scaledHeight, hints);
output = generateOutput(scaled);
} catch (Exception e) {
logger.error("generate image fail:[width=" + width + ",height=" + height + ",scaledWidth=" + scaledWidth + ",scaledHeight=" + scaledHeight + "]");
e.printStackTrace();
}
return output;
}
private BufferedImage scale(BufferedImage image, int width, int height, int scaledWidth, int scaledHeight, HashMap hints) {
if (scaledWidth < width && isUseHighScaleQuality()) {
do {
if (width > scaledWidth) {
width /= 2;
if (width < scaledWidth) {
width = scaledWidth;
}
}
if (height > scaledHeight) {
height /= 2;
if (height < scaledHeight) {
height = scaledHeight;
}
}
BufferedImage tmp = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g = tmp.createGraphics();
g.setRenderingHints(hints);
g.drawImage(image, 0, 0, width, height, null);
g.dispose();
image = tmp;
} while (width != scaledWidth || height != scaledHeight);
} else {
BufferedImage tmp = new BufferedImage(scaledWidth,scaledHeight, BufferedImage.TYPE_INT_RGB);
Graphics2D g = tmp.createGraphics();
g.setRenderingHints(hints);
g.drawImage(image, 0, 0, scaledWidth, scaledHeight, null);
g.dispose();
image = tmp;
}
return image;
}
private BufferedImage generateImage(InputStream input, int width, int height, HashMap hints) {
Document doc = tidy.parseDOM(input, null);
if (doc == null) {
logger.error("parse html file fail, invalid html file.");
return null;
}
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics = (Graphics2D) image.getGraphics();
graphics.setRenderingHints(RENDER_HINT);
Graphics2DRenderer renderer = new Graphics2DRenderer();
SharedContext context = renderer.getSharedContext();
context.setFontResolver(getFontResolver());
context.setNamespaceHandler(new XhtmlNamespaceHandler());
renderer.setDocument(doc, "");
renderer.layout(graphics, new Dimension(width, height));
renderer.render(graphics);
graphics.dispose();
return image;
}
private ByteArrayOutputStream generateOutput(BufferedImage image) {
ByteArrayOutputStream output = new ByteArrayOutputStream();
try {
switch (getImageFormat()) {
case JPG:
encodeJpg(image, output);
break;
case PNG:
default:
encodePng(image, output);
break;
}
} catch (ImageFormatException e) {
logger.error("generate image fail.");
e.printStackTrace();
output = null;
} catch (IOException e) {
logger.error("generate image fail.");
e.printStackTrace();
output = null;
}
return output;
}
private void encodeJpg(BufferedImage image, ByteArrayOutputStream output, float quality) throws ImageFormatException, IOException {
JPEGEncodeParam param = JPEGCodec.getDefaultJPEGEncodeParam(image);
param.setQuality(quality, true);
JPEGImageEncoder imageEncoder = JPEGCodec.createJPEGEncoder(output, param);
imageEncoder.encode(image);
}
private void encodeJpg(BufferedImage image, ByteArrayOutputStream output) throws ImageFormatException, IOException {
encodeJpg(image, output, getJpgQuality());
}
private void encodePng(BufferedImage image, ByteArrayOutputStream output) throws IOException {
PNGEncodeParam param = PNGEncodeParam.RGB.getDefaultEncodeParam(image);
PNGImageEncoder imageEncoder = new PNGImageEncoder(output, param);
imageEncoder.encode(image);
}
public void setJpgQuality(float jpgQuality) {
this.jpgQuality = jpgQuality;
}
public float getJpgQuality() {
return jpgQuality;
}
public void setImageFormat(ImageFormat imageFormat) {
this.imageFormat = imageFormat;
}
public ImageFormat getImageFormat() {
return imageFormat;
}
public void setFontResolver(ChineseFontResolver fontResolver) {
this.fontResolver = fontResolver;
}
public ChineseFontResolver getFontResolver() {
return fontResolver;
}
public void setUseHighScaleQuality(boolean useHighScaleQuality) {
this.useHighScaleQuality = useHighScaleQuality;
}
public boolean isUseHighScaleQuality() {
return useHighScaleQuality;
}
}
enum ImageFormat {
JPG, PNG
}
为了使用中文字体，需要手工加载中文字体，这里都是用truetype字体：
/**
* 中文字体支持，默认使用微软雅黑
*
*/
public class ChineseFontResolver extends AWTFontResolver {
private static Font DEFAULT_FONT;
private String fontPath;
public ChineseFontResolver() {
super();
}
public void init() {
try {
InputStream input = new FileInputStream(new File(getFontPath() + "msyh.ttf"));
Font font = Font.createFont(Font.TRUETYPE_FONT, input);
font = font.deriveFont(12.0F);
setFontMapping("微软雅黑", font);
DEFAULT_FONT = font;
setFontMapping("arial", font);
setFontMapping("serif", font);
setFontMapping("SansSerif", font);
setFontMapping("Monospaced", font);
} catch (FontFormatException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
protected Font resolveFont(SharedContext ctx, String font, float size, IdentValue weight, IdentValue style, IdentValue variant) {
Font result = super.resolveFont(ctx, "微软雅黑", size, weight, style, variant);
if (result == null) {
result = DEFAULT_FONT;
}
return result;
}
public void setFontPath(String fontPath) {
this.fontPath = fontPath;
}
public String getFontPath() {
return fontPath;
}
}
truetype的微软雅黑结合ImageGenerator中的RENDER_HINT，渲染出来的中文字体质量还是相当不错的。
使用方法就像这样，为了不出现乱码，最好全部都是用UTF-8编码:
ByteArrayOutputStream output = null;
try {
Map data = new HashMap();
String html = getTemplateParser().parse("template.ftl", data);//使用freemarker填充数据
InputStream input = new ByteArrayInputStream(html.getBytes(Charset.forName("UTF-8")));
output = getImageGenerator().html2Image(input, 1260, 64);
//for test
// FileOutputStream file = new FileOutputStream(new File("d://images//result.jpg"));
// file.write(output.toByteArray());
// file.flush();
// file.close();
} catch (TemplateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
以上代码是使用模板来生成图片，网站截图只要稍微修改一下代码即可，以下是个简单的例子：
public class Main {
public static void main(String[] args) {
try {
Tidy tidy = new Tidy();
tidy.setQuiet(true);
tidy.setXHTML(true);
tidy.setHideComments(true);
tidy.setInputEncoding("UTF-8");
tidy.setOutputEncoding("UTF-8");
tidy.setShowErrors(0);
tidy.setShowWarnings(false);
//for test start
FileOutputStream output = new FileOutputStream(new File("d:/1234.png"));
URL url=new URL("http://www.baidu.com");
URLConnection conn=url.openConnection();
conn.connect();
InputStream is=conn.getInputStream();
BufferedReader br=new BufferedReader(new InputStreamReader(is,"gbk"));
String s = "";
StringBuffer sb = new StringBuffer("");
while ((s = br.readLine()) != null) {
sb.append(s + "\r\n");
}
ByteArrayInputStream bis = new ByteArrayInputStream(sb.toString().getBytes("UTF-8"));
//for test end
Document doc = tidy.parseDOM(bis, null);
Graphics2DRenderer g2r = new Graphics2DRenderer();
g2r.setDocument(doc,"");
//这里其实还是使用固定的width、height去渲染网页，但是可以设置一个较大的值
Dimension dim = new Dimension(1024, 2000);
BufferedImage buff = new BufferedImage((int)dim.getWidth(), (int)dim.getHeight(), BufferedImage.TYPE_INT_RGB);
Graphics2D g = (Graphics2D)buff.getGraphics();
g2r.layout(g, new Dimension(1024, 2000));
g.dispose();
//这里获取真正的网页大小，如果页面有背景图设了repeat，会导致无法获取真实大小
Rectangle rect = g2r.getMinimumSize();
buff = new BufferedImage((int)rect.getWidth(), (int)rect.getHeight(), BufferedImage.TYPE_INT_RGB);
g = (Graphics2D)buff.getGraphics();
g2r.render(g);
g.dispose();
PNGEncodeParam param = PNGEncodeParam.RGB.getDefaultEncodeParam(buff);
PNGImageEncoder imageEncoder = new PNGImageEncoder(output, param);
imageEncoder.encode(buff);
output.flush();
output.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
