java使用ImageReader判斷圖片的類型

import java.io.File;
import java.io.IOException;
import java.util.Iterator;

import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;
public class DetermineFormatOfAnImage {

public static void main(String[] args) throws IOException {

    // get image format in a file
    File file = new File("newimage.jpg");

    // create an image input stream from the specified file
    ImageInputStream iis = ImageIO.createImageInputStream(file);

    // get all currently registered readers that recognize the image format
    Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);

    if (!iter.hasNext()) {
        throw new RuntimeException("No readers found!");
    }

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

    System.out.println("Format: " + reader.getFormatName());

    // close stream
    iis.close();

}


}
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