前言
最近在加载图片时，由于需要对不同图片使用不同的加载方式，因此需要通过判断图片的类型进行条用不同的接口。
因此整理如下内容。
常见的图片格式头文件代码
PS：如下是十六进制
- JPEG (jpg) 文件头：FFD8FF
- PNG (png) 文件头：
89504E47（打印png的值是：89506082） - GIF (gif) 文件头：47494638
- Windows Bitmap (bmp) 文件头：424D
- TIFF (tif) 文件头：49492A00
总结
- gif，jpg，bmp测试通过
- tiff由于没有图片，没有测试
- png的判断存在问题，上面也备注了，打印值跟89 50 4E 47 不一样
正文
下面是测试的代码片段。
PS：代码中判断的是十进制，需要转换一下
gif 格式
/**
* gif (十六进制 ： 47 49 46 38)
*
* @param file
* @return
*/
public static boolean isGifFile(File file) {
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(file);
int[] buffer = new int[5];
buffer[0] = fileInputStream.read();
buffer[1] = fileInputStream.read();
buffer[2] = fileInputStream.read();
buffer[3] = fileInputStream.read();
fileInputStream.skip(fileInputStream.available() - 1);
buffer[4] = fileInputStream.read();
return buffer[0] == 71 && buffer[1] == 73 && buffer[2] == 70 && buffer[3] == 56;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != fileInputStream) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return false;
}
jpg 格式
/**
* jpg (十六进制 ： FF D8 FF)
*
* @param file
* @return
*/
public static boolean isJpgFile(File file) {
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(file);
int buffer[] = new int[4];
buffer[0] = fileInputStream.read();
buffer[1] = fileInputStream.read();
fileInputStream.skip(fileInputStream.available() - 2);
buffer[2] = fileInputStream.read();
buffer[3] = fileInputStream.read();
return buffer[0] == 255 && buffer[1] == 216 && buffer[2] == 255;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}finally {
if (null != fileInputStream) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return false;
}
bmp格式
/**
* bmp (十六进制 ： 42 4D)
*
* @param file
* @return
*/
public static boolean isBmpFile(File file) {
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(file);
int buffer[] = new int[4];
buffer[0] = fileInputStream.read();
buffer[1] = fileInputStream.read();
fileInputStream.skip(fileInputStream.available() - 2);
buffer[2] = fileInputStream.read();
buffer[3] = fileInputStream.read();
return buffer[0] == 66 && buffer[1] == 77;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}finally {
if (null != fileInputStream) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return false;
}
tiff格式
/**
* tiff (十六进制 ： 49 49 2A 00)
*
* @param file
* @return
*/
public static boolean isTiffFile(File file) {
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(file);
int buffer[] = new int[4];
buffer[0] = fileInputStream.read();
buffer[1] = fileInputStream.read();
fileInputStream.skip(fileInputStream.available() - 2);
buffer[2] = fileInputStream.read();
buffer[3] = fileInputStream.read();
return buffer[0] == 73 && buffer[1] == 73 && buffer[2] == 42 && buffer[2] == 00;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}finally {
if (null != fileInputStream) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return false;
}
png格式
参考网上的值，这个png测试不通过，打印对应的值是 89506082 （十六进制）
/**
* png (十六进制 ： 89 50 4E 47)
*
* @param file
* @return
*/
public static boolean isPngFile(File file) {
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(file);
int buffer[] = new int[4];
buffer[0] = fileInputStream.read();
buffer[1] = fileInputStream.read();
fileInputStream.skip(fileInputStream.available() - 2);
buffer[2] = fileInputStream.read();
buffer[3] = fileInputStream.read();
return buffer[0] == 137 && buffer[1] == 80 && buffer[2] == 78 && buffer[3] == 71;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
if (null != fileInputStream) {
try {
fileInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return false;
}
