本文实例为大家分享了Java实现按比例缩小图片的具体代码，供大家参考，具体内容如下
使用spring注解上传文件@RequestParam(value="", required=true)，required为true时不能传入空值，为false时反之；UploadFile.getOriginalFilename()获取上传的文件的文件名；System.nanoTime()返回当前时间的纳秒，用做文件名；FileUtils.writeByteArrayToFile()上传文件到本地目录；使用BufferedImage将图片加载到内存中，然后对图片进行修改如大小变换、图片变灰、设置透明等。
效果图：
HTML：
<div class="form-group">
<label class="col-lg-1 col-md-1 col-sm-2 col-xs-2 label-size"><span class="c-red">*</span>头像：</label>
<div class="col-lg-4 col-md-4 col-sm-4 col-xs-4 img-padding-zero">
<div>
<span id="Upload_ph" class="img-hide">
<input type="file" title="" id="UploadFile" name="UploadFile" multiple="" class="img-input">
</span>
<span>
<img alt="" src="${ctx}/UserManages/reveal_photo.do?file=tree.png">
<a class="a-word" style="cursor:pointer;">上传图片</a>
<a id="showApellation" class="a-word" style="font-size:12px;"></a>
</span>
</div>
<div>
<img src="${ctx}/UserManages/reveal_photo.do?file=noImg.png" class="img-padding" width="198" height="198" alt="" id="imgOperPhoto1" onload="AutoResizeImage(198, 198, this)" title="用于头像显示">
<img src="${ctx}/UserManages/reveal_photo.do?file=noImg_tab.png" class="img-padding" width="28" height="40" alt="" id="imgOperPhoto3" title="用于列表显示">
</div>
</div>
</div>form表单提交到java：
@SuppressWarnings("unused")
@RequestMapping(value="/IntOpers")
private void IntOper(@RequestParam(value="UploadFile", required=true) MultipartFile UploadFile, PrintWriter pw, HttpServletRequest request) throws IOException {
String StrReturn = "error", FileName = "", ext = "";
long time = 0;
if (!UploadFile.isEmpty()) {
if (UploadFile != null) {
String fullName = UploadFile.getOriginalFilename();
ext = fullName.substring(fullName.lastIndexOf("."));//获取扩展名称
time = System.nanoTime();
FileName = time + ext;//设置文件保存的名称
//原图
String upDir = "F:/java/upload-ssm";//文件上传路径
FileUtils.writeByteArrayToFile(new File(upDir, FileName), UploadFile.getBytes());
//缩小图片
Image srcFile = ImageIO.read(new File(upDir + "/" + FileName));
BufferedImage tag = new BufferedImage(28, 40, BufferedImage.TYPE_INT_RGB);
tag.getGraphics().drawImage(srcFile, 0, 0, 28, 40, null);
String FileName_tab = time + "_tab" + ext;//设置文件保存的名称
FileOutputStream out = new FileOutputStream(upDir + "/" + FileName_tab);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
JPEGEncodeParam jep = JPEGCodec.getDefaultJPEGEncodeParam(tag);
jep.setQuality(1f, true);
encoder.encode(tag, jep);
out.close();
StrReturn = "success";
}
}
pw.write(StrReturn);
}以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程网。
