java图⽚类型判断
⽅法⼀：根据图⽚url中的携带的ContentType信息判断图⽚的类型，如果图⽚被强制修改了图⽚的类型会有问题
/**
* 根据url中ContentType判断问价格式
* @param imgUrl
* @return
*/
public static String getImageType(String imgUrl) {
BufferedInputStream bis = null;
HttpURLConnection urlconnection = null;
String prefix = "";
try {
URL url = new URL(imgUrl);
urlconnection = (HttpURLConnection) url.openConnection();
bis = new InputStream());
String imageTypes = HttpURLConnection.guessContentTypeFromStream(bis);
if (ains("/")) {
prefix = imageTypes.substring(imageTypes.lastIndexOf("/"));
prefix = placeFirst("/", ".");
return prefix;
}
} catch (IOException e) {
e.printStackTrace();
}
return ".jpg";
}
⽅法⼆：将图⽚的信息读成流转16进制，根据⽂件流判断⽂件类型（推荐使⽤）
public class ImageTypeUtils {
/**
常⽤⽂件的⽂件头如下：(以前六位为准)
JPEG (jpg)，⽂件头：FFD8FF
PNG (png)，⽂件头：89504E47
GIF (gif)，⽂件头：47494638
TIFF (tif)，⽂件头：49492A00
Windows Bitmap (bmp)，⽂件头：424D
CAD (dwg)，⽂件头：41433130
Adobe Photoshop (psd)，⽂件头：38425053
Rich Text Format (rtf)，⽂件头：7B5C727466
XML (xml)，⽂件头：3C3F786D6C
HTML (html)，⽂件头：68746D6C3E
Email [thorough only] (eml)，⽂件头：44656C69766572792D646174653A
Outlook Express (dbx)，⽂件头：CFAD12FEC5FD746F
Outlook (pst)，⽂件头：2142444E
MS Word/Excel (doc)，⽂件头：D0CF11E0
MS Access (mdb)，⽂件头：5374616E64617264204A
WordPerfect (wpd)，⽂件头：FF575043
Postscript (ps)，⽂件头：252150532D41646F6265
Adobe Acrobat (pdf)，⽂件头：255044462D312E
Quicken (qdf)，⽂件头：AC9EBD8F
Windows Password (pwl)，⽂件头：E3828596
ZIP Archive (zip)，⽂件头：504B0304
RAR Archive (rar)，⽂件头：52617221
Wave (wav)，⽂件头：57415645
AVI (avi)，⽂件头：41564920
Real Audio (ram)，⽂件头：2E7261FD
Real Media (rm)，⽂件头：2E524D46
MPEG (mpg)，⽂件头：000001BA
MPEG (mpg)，⽂件头：000001BA
MPEG (mpg)，⽂件头：000001B3
Quicktime (mov)，⽂件头：6D6F6F76
Windows Media (asf)，⽂件头：3026B2758E66CF11
MIDI (mid)，⽂件头：4D546864
public static final String TYPE_JPG = ".jpg";
public static final String TYPE_GIF = ".gif";
public static final String TYPE_PNG = ".png";
public static final String TYPE_BMP = ".bmp";
public static final String TYPE_WEBP = ".webp";
public static final String TYPE_TIF = ".tif";
// public static final String TYPE_UNKNOWN = "unknown";
public static void main(String[] args) throws FileNotFoundException {
File pdfFile = new File("C:\\Users\\Public\\Pictures\\Sample Pictures\\F35245_113_P2.jpg");
//test code
System.out.println("图⽚格式1： " + getPicType(new FileInputStream(pdfFile)));
}
/**
* byte数组转换成16进制字符串
* @param src
* @return
*/
public static String bytesToHexString(byte[] src){
StringBuilder stringBuilder = new StringBuilder();
if (src == null || src.length <= 0) {
return null;
}
for (int i = 0; i < src.length; i++) {
int v = src[i] & 0xFF;
String hv = HexString(v);
if (hv.length() < 2) {
stringBuilder.append(0);
}
stringBuilder.append(hv);
}
String();
}
/**
* 根据⽂件流判断图⽚类型
* @param fis
* @return jpg/png/gif/bmp
*/
public static String getPicType(FileInputStream fis) {
//读取⽂件的前⼏个字节来判断图⽚格式
byte[] b = new byte[4];
try {
String type = bytesToHexString(b).toUpperCase();
if (ains("FFD8FF")) {
return TYPE_JPG;
} else if (ains("89504E47")) {
return TYPE_PNG;
} else if (ains("47494638")) {
return TYPE_GIF;
} else if (ains("424D")) {
return TYPE_BMP;
}else ains("52494646")){
return TYPE_WEBP;
return TYPE_WEBP;
}else ains("49492A00")){
return TYPE_TIF;
}else{
return TYPE_JPG;
}
} catch (IOException e) {
e.printStackTrace();
}finally{
if(fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
/**
* 根据⽂件流判断图⽚类型
* @param fis
* @return jpg/png/gif/bmp
*/
public static String getPicType2(InputStream fis) {
//读取⽂件的前⼏个字节来判断图⽚格式
byte[] b = new byte[4];
try {
String type = bytesToHexString(b).toUpperCase();
if (ains("FFD8FF")) {
return TYPE_JPG;
} else if (ains("89504E47")) {
return TYPE_PNG;
} else if (ains("47494638")) {
return TYPE_GIF;
} else if (ains("424D")) {
return TYPE_BMP;
}else ains("52494646")){
return TYPE_WEBP;
}else ains("49492A00")){
return TYPE_TIF;
}else{
return null;
}
} catch (IOException e) {
e.printStackTrace();
}finally{
if(fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
}
相关问题：webp图⽚ios⼿机和ie浏览器显⽰会有问题（可转换为png图⽚）实例：
java修改html文件url1：原图⽚路径
path:⽂件临时存储路径
也可转换为jpg,png等格式
String imgType = PicType(new FileInputStream(url1));
if (imgType.equals(".webp")) {//图⽚转化
ImageReader reader = ImageReadersByMIMEType("image/webp").next();    WebPReadParam readParam = new WebPReadParam();
readParam.setBypassFiltering(true);
reader.setInput(new FileImageInputStream(new File(url)));
url = path + UUID.randomUUID() + ".png";
BufferedImage image = ad(0, readParam);
ImageIO.write(image, "png", new File(url));
}

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