如何在java中获取图像大小

Question

Application wants to check existing uploaded image, does it exceed maximum limit or not.

Here is the controller

@RequestMapping(value = "/product/{id}/{id2}", method = RequestMethod.GET,
      produces = {MediaType.APPLICATION_JSON_VALUE})
  @ResponseBody
  public RestMethod validateFileSize(HttpSession session, 
          @PathVariable("id") String fileName, @PathVariable("id2") String fileType) throws Exception {
      if (!fileName.isEmpty()) {
        URL url = new URL("http://localhost:8080/MyShop/image/" + fileName + "." + fileType +"/");

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        InputStream is = url.openStream();
        byte[] b = new byte[2^16];
        int read = is.read(b);

        while (read > -1) {
            baos.write(b, 0, read);
            read = is.read(b);
        }

        int size = baos.toByteArray().length;

        if (size <= 102400) {
            return new RestMethod(null, true);
        } else {
            return new RestMethod(null, false);
        }
      } else {
        throw new ApplicationException(ErrorCategory.UNSPECIFIED, "noFile");
      }
    } catch (Exception e) {
      if (e instanceof ApplicationException) {
        ApplicationException applicationException = (ApplicationException) e;
        return new RestMethod(applicationException.getErrorMessage(), false);
      } else {
        return new RestMethod(e.getMessage(), false);
      }
    }
  }

Actual size is 760KB which is 77820 Byte, but it returned 3475. Why didn't size return correct size of the image? How to get image actual size?

Answer 1

Most probably it is a file issue or somehow you are reading a wrong file or there is some issue in code(or process) of reading the file.

Did your try with another image file ? Try with sample image files that your OS usually provides. Those usually will have correct encoding and meta data.

The part of your code which gets the size of image is correct. I copied that part and put it inside a desktop java program and i got the correct file size.

Your code which worked for me in desktop java program below.

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);


    }
}

Here is an example program which I use as a reference when dealing with images which reads and writes an image file. This may help you as well.

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());
    }
}