Java Glossary : ImageIO

Java definitions: 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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ImageIO

javax.imageio.ImageIO lets you save and restore Images to disk in a platform independent format. It works using plug-in modules that handle various formats including "gif", "png" and "jpeg" (all lower case, or all upper case, but not mixed). "jpeg" or "jpg" is acceptable. Use ImageIO.getWriterFormatNames() to find out which types are supported on your machine.

With ImageIO, instead of Image you use BufferedImage which is a subclass of Image, and can thus be used in any of the familiar tools that work with Images. Introduced with Java 1.4.

Creating an Image from raw bytes

Here raw bytes represent the image of a *.gif, *.png or *.jpg file in RAM.

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import javax.imageio.ImageIO;

BufferedImage image = ImageIO.read ( new ByteArrayInputStream ( rawImageBytes ) );

Loading a BufferedImage from a file

import java.awt.image. BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;

BufferedImage image = ImageIO.read( new File( "rabbit.jpg" ) );

Loading a BufferedImage from an URL

import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;

BufferedImage image = null;
try
   {
   image = ImageIO.read( url );
   }
catch ( IOException e )
   {
   System.out.println( "image missing" );
   }

Saving a BufferedImage as a file

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;

ImageIO.write( aBufferedImage, "jpeg" /* "png" "jpeg" format desired, no "gif" yet. */
               , new File ( "snap.jpg" ) /* target */ );

Converting Image to BufferedImage

import java.awt.image.BufferedImage;
import java.awt.Image;
...
// convert Image to BufferedImage
BufferedImage bufferedImage = new BufferedImage ( imageWidth,
                                                  imageHeight,
                                                  BufferedImage.TYPE_INT_BGR  );
bufferedImage.createGraphics().drawImage( image, 0, 0, this /* observer */ );

Sun's docs on ImageIO : available:

on the web at java.Sun.com
on J: in the JDK 1.4.2_04: J:\j2sdk1.4.2_04\docs\guide\imageio\index.html
on J: in the JDK 1.5 beta: J:\Program Files\Java\j2sdk1.5.0\docs\guide\imageio\index.html

BufferedImage ¤ GIF encoder ¤ GIF ¤ Image ¤ JPEG encoder ¤ JPEG ¤ PNG

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