很可能是文件问题，或者您以某种方式读取了错误的文件，或者读取文件的代码（或过程）存在问题。
您是否尝试过使用另一个图像文件？尝试使用您的操作系统通常提供的示例图像文件。那些通常会有正确的编码和元数据。
获取图像大小的代码部分是正确的。我复制了那部分并将其放入桌面 java 程序中，我得到了正确的文件大小。
您的代码在下面的桌面 java 程序中为我工作。
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;
public class SimpleConvertImage2 {
public static void main(String[] args) throws FileNotFoundException, IOException {
/*
* 1. How to convert an image file to byte array?
*/
File file = new File("C:\\rose.jpg");
FileInputStream fis = new FileInputStream(file);
//create FileInputStream which obtains input bytes from a file in a file system
//FileInputStream is meant for reading streams of raw bytes such as image data. For reading streams of characters, consider using FileReader.
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
//InputStream is = url.openStream();
byte[] b = new byte[2^16];
int read = fis.read(b);
while (read > -1) {
baos.write(b, 0, read);
read = fis.read(b);
}
int size = baos.toByteArray().length;
System.out.println("image size original code : " + size);
}
}
这是一个示例程序，我在处理读取和写入图像文件的图像时用作参考。这也可能对您有所帮助。
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;
public class SimpleConvertImage {
public static void main(String[] args) throws FileNotFoundException, IOException {
/*
* 1. How to convert an image file to byte array?
*/
File file = new File("C:\\rose.jpg");
FileInputStream fis = new FileInputStream(file);
//create FileInputStream which obtains input bytes from a file in a file system
//FileInputStream is meant for reading streams of raw bytes such as image data. For reading streams of characters, consider using FileReader.
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
try {
for (int readNum; (readNum = fis.read(buf)) != -1;) {
//Writes to this byte array output stream
bos.write(buf, 0, readNum);
System.out.println("read " + readNum + " bytes,");
}
} catch (IOException ex) {
Logger.getLogger(SimpleConvertImage.class.getName()).log(Level.SEVERE, null, ex);
}
byte[] bytes = bos.toByteArray();
int size = bytes.length;
System.out.println("image size : " + size);
/*
* 2. How to convert byte array back to an image file?
*/
ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
Iterator<?> readers = ImageIO.getImageReadersByFormatName("jpg");
//ImageIO is a class containing static methods for locating ImageReaders
//and ImageWriters, and performing simple encoding and decoding.
ImageReader reader = (ImageReader) readers.next();
Object source = bis;
ImageInputStream iis = ImageIO.createImageInputStream(source);
reader.setInput(iis, true);
ImageReadParam param = reader.getDefaultReadParam();
Image image = reader.read(0, param);
//got an image file
BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_RGB);
//bufferedImage is the RenderedImage to be written
Graphics2D g2 = bufferedImage.createGraphics();
g2.drawImage(image, null, null);
File imageFile = new File("C:\\newrose2.jpg");
ImageIO.write(bufferedImage, "jpg", imageFile);
System.out.println(imageFile.getPath());
}
}