Java: convert image to byte array, convert byte array to image
If you want to convert an image to a byte array, and then convert the byte array back to image, this is the code.
This program was initially for a centralized file upload and management system, which uses Web Service to do file transfer. Although Web Service is not good for transferring large files, images are normally smaller, and therefore may work this way. On one side, the image is converted to an array of bytes, and sent to the other side. Then the other side converts the byte array back to the image.
If you are interested in transferring images using Web Service, Please read my previous post about this topic. Here is a post about the solution of using Web Service to transfer files.
You can download the code here or copy the code 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 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()); } }
Here is a simple version which has exactly the same function. It uses the BufferedImage class, which is a proved more efficient way.
