java中对图片文件的获取

系统中某些图片可能已经被修改了后缀名，所以不能只是对文件名进行判断。下面的示例代码就是如何判断一个图片的具体类型的。

public static void main(String[] args) {
File f = new File("d://test.jpg");
if (f.exists()) {
System.out.println(getFormatInFile(f));
}
}

// Returns the format of the image in the file 'f'.
// Returns null if the format is not known.
public static String getFormatInFile(File f) {
return getFormatName(f);
}

// Returns the format name of the image in the object 'o'.
// Returns null if the format is not known.
private static String getFormatName(Object o) {
try {
// Create an image input stream on the image
ImageInputStream iis = ImageIO.createImageInputStream(o);

// Find all image readers that recognize the image format
Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);
if (!iter.hasNext()) {
// No readers found
return null;
}

// Use the first reader
ImageReader reader = iter.next();

// Close stream
iis.close();

// Return the format name
return reader.getFormatName();
} catch (IOException e) {
//
}

// The image could not be read
return null;
}