Java工具包

压缩图片

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/**
* 根据指定大小压缩图片
*
* @param imageBytes 源图片字节数组
* @param desFileSize 指定图片大小,单位kb
* @return 压缩质量后的图片字节数组
*/
public static byte[] compressPicForScale(byte[] imageBytes, long desFileSize) {
if (imageBytes == null || imageBytes.length <= 0 || imageBytes.length < desFileSize * 1024) {
return imageBytes;
}
long srcSize = imageBytes.length;
double accuracy = getAccuracy(srcSize / 1024);
try {
while (imageBytes.length > desFileSize * 1024) {
ByteArrayInputStream inputStream = new ByteArrayInputStream(imageBytes);
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(imageBytes.length);
Thumbnails.of(inputStream)
.scale(accuracy)
.outputQuality(accuracy)
.toOutputStream(outputStream);
imageBytes = outputStream.toByteArray();
}
} catch (Exception e) {
System.out.println("【图片压缩】msg=图片压缩失败!" + e);
}
return imageBytes;
}

/**
* 自动调节精度(经验数值)
*
* @param size 源图片大小
* @return 图片压缩质量比
*/
private static double getAccuracy(long size) {
double accuracy;
if (size < 2048) {
accuracy = 0.8;
} else if (size < 7168) {
accuracy = 0.7;
} else if (size < 10240) {
accuracy = 0.5;
} else {
accuracy = 0.4;
}
return accuracy;
}

file转MultipartFile

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public static MultipartFile getMultipartFile(File file) {
FileItem item = new DiskFileItemFactory().createItem("file"
, MediaType.MULTIPART_FORM_DATA_VALUE
, true
, file.getName());
try (InputStream input = new FileInputStream(file);
OutputStream os = item.getOutputStream()) {
// 流转移
IOUtils.copy(input, os);
} catch (Exception e) {
throw new IllegalArgumentException("Invalid file: " + e, e);
}
return new CommonsMultipartFile(item);
}