WEB实战：头像裁剪

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参考http://deepliquid.com/projects/Jcrop/demos.php?demo=handler，代码如下：

    var showCoords = function(c){        $('#x').val(c.x);        $('#y').val(c.y);        $('#w').val(c.w);        $('#h').val(c.h);    }    $('#jcrop_target').Jcrop({            onChange:showCoords,            onSelect:showCoords    });

获取截图区域的坐标信息，这里需要考虑图片长宽的缩放比例，计算好准确的数值（x、y、w、h）传给服务器，由java类在原图的基础上进行裁剪。

1.根据图片File对象或者流，转换成BufferedImage对象

BufferedImage bi = ImageIO.read(file);或者ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());BufferedImage bi = ImageIO.read(bis);

ImageIO还支持其它参数如下：

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2.获取ImageWriter

private static ImageWriter getImageWriter(BufferedImage bi) {    ImageWriter writer = null;    ImageTypeSpecifier type = ImageTypeSpecifier.createFromRenderedImage(bi);    Iterator iter = ImageIO.getImageWriters(type, "jpg");    if (iter.hasNext()) {        writer = (ImageWriter) iter.next();    }    return writer;}

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3.设置Writer参数

ImageWriteParam param = writer.getDefaultWriteParam();param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);param.setCompressionQuality((float) 1.0);param.setSourceRegion(new Rectangle(x, y, width, height));

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4.输出Image文件或者流

IIOImage iioImage = new IIOImage(bi, null, null);ByteArrayOutputStream bos2 = new ByteArrayOutputStream();ImageOutputStream outputStream = ImageIO.createImageOutputStream(bos2);writer.setOutput(outputStream);writer.write(null, iioImage, param);

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5.将流对象保存到文件系统

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