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 ConvertImage { public static void main(String[] args) throws FileNotFoundException, IOException { /* * In this function the first part shows how to convert an image file to * byte array. The second part of the code shows how to change byte array * back to a image */ File file = new File("C:\\rose.jpg"); System.out.println(file.exists() + "!!"); 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. //InputStream in = resource.openStream(); ByteArrayOutputStream bos = new ByteArrayOutputStream(); byte[] buf = new byte[1024]; try { for (int readNum; (readNum = fis.read(buf)) != -1;) { bos.write(buf, 0, readNum); //no doubt here is 0 /*Writes len bytes from the specified byte array starting at offset off to this byte array output stream.*/ System.out.println("read " + readNum + " bytes,"); } } catch (IOException ex) { Logger.getLogger(ConvertImage.class.getName()).log(Level.SEVERE, null, ex); } byte[] bytes = bos.toByteArray(); //bytes is the ByteArray we need /* * The second part shows how to convert byte array back to an image file */ //Before is how to change ByteArray back to Image ByteArrayInputStream bis = new ByteArrayInputStream(bytes); Iterator readers = ImageIO.getImageReadersByFormatName("jpg"); //ImageIO is a class containing static convenience methods for locating ImageReaders //and ImageWriters, and performing simple encoding and decoding. ImageReader reader = (ImageReader) readers.next(); Object source = bis; // File or InputStream, it seems file is OK ImageInputStream iis = ImageIO.createImageInputStream(source); //Returns an ImageInputStream that will take its input from the given Object 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); //"jpg" is the format of the image //imageFile is the file to be written to. System.out.println(imageFile.getPath()); } }