识别真实图片格式

public class ImageFilter {

final static String tag = "ImageFilter";

public enum Type {
JPG, // SOI(2 bytes):0xFFD8
GIF, // Signature(3 bytes) Version(3 bytes): 0x47494638 0x3961____
PNG, // Signature(8 bytes):0x89504E47 0x0D0A1A0A
BMP, // type(2 bytes):0x424D(Windows系统格式，而OS/2系统并未普及)
SVG, // xml文件 读取前256个字节判断是否含有"svg"
/*----------------------------------------------------------------------------------
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 100 30" version="1.1"
xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<desc>Example Use03 - 'use' with a 'transform' attribute</desc>
<defs>
<rect id="MyRect" x="0" y="0" width="60" height="10"/>
</defs>
<rect x=".1" y=".1" width="99.8" height="29.8"
fill="none" stroke="blue" stroke-width=".2" />
<use xlink:href="#MyRect"
transform="translate(20,2.5) rotate(10)" />
</svg>
--------------------------------------------------------------------------------- */
ICO, // type(1、2字节保留，第3、4字节为类型):0x00000100
TIFF, // header(12字节为 II或MM，34字节 值为42)
UNKNOWN;
}

/**
* 查询图像的真实格式
*
* @param filePath
*            图像文件的绝对路径
* @return
*/
static public Type getImageFormat(String filePath)
throws FileNotFoundException {
Type typeRet = Type.UNKNOWN;

do {
File imageFile = new File(filePath);
if (null == imageFile || !imageFile.exists() || !imageFile.isFile()) {
throw new FileNotFoundException("\"" + filePath + "\""
+ " not exists!");
// break;
}
FileInputStream fis = new FileInputStream(imageFile);
typeRet = getImageFormat(fis);
} while (false);

return typeRet;
}

static public Type getImageFormat(InputStream inputStream) {
Type typeRet = Type.UNKNOWN;
BufferedInputStream bis = null;
try {
do {
if (null == inputStream || inputStream.available() < 1)
break;
bis = new BufferedInputStream(inputStream);
byte[] simpleByte = inputStream2Bytes(bis, 8);
if (null == simpleByte)
break;
typeRet = checkImageFormat(simpleByte);
if (Type.UNKNOWN == typeRet) {// SVG 处理
byte[] detailByte = inputStream2Bytes(bis, 256);
if (detailByte.length < 256)
break;
//
if (isSVG(detailByte)) {
typeRet = Type.SVG;
break;
}
}
} while (false);
} catch (IOException ioe) {
ioe.printStackTrace();
}

return typeRet;
}

static public Type getImageFormat(byte[] imageBytes) {
Type typeRet = checkImageFormat(imageBytes);

if (Type.UNKNOWN == typeRet) {
// 判断是不是svg
// 1.判断文件大小是否大于256字节，小于则不支持，认为非svg
// 2.大于等于256字节，再读取前256个字节转换字符串，如果含有svg则是svg
do {
// step 1
if (imageBytes.length < 256)
break;
// step 2
if (isSVG(imageBytes)) {
typeRet = Type.SVG;
break;
}
} while (false);

}

return typeRet;
}

/**
* 读取前8个字节 1.首先判断前两个字节 JPG:0xFFD8 GIF:0x4749 PNG:0x8950 BMP:0x424D
* ICO:0x0000 SVG:不确定 需要额外判断
*
* @param imageBytes
*            长度为8
* @return 图像类型
*/
static private Type checkImageFormat(byte[] imageBytes) {
Type typeRet = Type.UNKNOWN;

do {
if (null == imageBytes || imageBytes.length < 8)
break;

// s vlaue = ;

// Log.d(tag, String.format("value:%x", vlaue));
System.out.println(String.format("value:%x",
(short) (imageBytes[0] << 8 | imageBytes[1])));
switch ((short) (imageBytes[0] << 8 | imageBytes[1])) {
case (short) 0xFFD8:// 确定为JPG
typeRet = Type.JPG;
break;
case (short) 0x4749: {// 可能为GIF
if (imageBytes[2] == 0x46) {// 确定为GIF
typeRet = Type.GIF;
}
}
break;
case (short) 0x8950: {// 可能为PNG
if ((short) (imageBytes[2] << 8 | imageBytes[3]) == 0x4E47
&& (imageBytes[4] << 24 | imageBytes[5] << 16
| imageBytes[6] << 8 | imageBytes[7]) == 0x0D0A1A0A) {
// 确定为PNG
typeRet = Type.PNG;
}

}
break;
case (short) 0x424D: // 确定为 windows平台的BMP
typeRet = Type.BMP;
break;
case (short) 0x0000: { // 可能为 ico
System.out.println("ico:"
+ (short) (imageBytes[2] << 8 | imageBytes[3]));
if ((short) (imageBytes[2] << 8 | imageBytes[3]) == 0x0100) {
// 确定为 ico
typeRet = Type.ICO;
}
}
break;
case (short) ('M' << 8 | 'M'):
case (short) ('I' << 8 | 'I'): {
if ((short) (imageBytes[2] << 8 | imageBytes[3]) == 42) {
// 确定为 tiff
typeRet = Type.TIFF;
}
}
break;
default:
typeRet = Type.UNKNOWN;
}

} while (false);

return typeRet;
}

static private boolean isSVG(byte[] svg256bytes) {
boolean bRet = false;
do {
if (null == svg256bytes || svg256bytes.length < 60)
break;
try {
String svg = new String(svg256bytes, "UTF-8");
System.out.println("SVG:" + svg);
if (svg != null && svg.contains("svg")) {
bRet = true;
}
} catch (UnsupportedEncodingException uee) {
uee.printStackTrace();
}

} while (false);

return bRet;
}

static void ListFilesInDirectory(String path) throws FileNotFoundException {
File file = new File(path);
File[] files = file.listFiles();
Type tyep;
for (File fl : files) {
if (fl.isDirectory())
ListFilesInDirectory(fl.toString());
else {
System.out.println();

String filePath = fl.getAbsolutePath();
tyep = ImageFilter.getImageFormat(filePath);
String strType = tyep.toString();
String str = filePath.substring(filePath.lastIndexOf('.') + 1).toUpperCase();
//				System.out.println(str);
if(!strType.equals(str)){
System.out.println("文件名   = " + filePath
+ "       type = " + strType);
}

}
}
}

/**
* 数据流转成byte[];
*
* @param inputStream
* @param length
*            要转换几个长度的Byte
* @return
*/
static private byte[] inputStream2Bytes(InputStream inputStream, int length) {
byte[] byteRet = null;

try {
do {
if (null == inputStream || inputStream.available() < length
|| length < 1)
break;
inputStream.mark(length);
byteRet = new byte[length];
inputStream.read(byteRet);
inputStream.reset();

} while (false);
} catch (IOException ioe) {
ioe.printStackTrace();
}

return byteRet;
}

public static void main(String[] args) {

try {
String path = "D://test";

ListFilesInDirectory(path);

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}