java.awt.Image 的几样经验

java.awt.Image 的几样经验

1. 从文件/或者Url中获得Image.
java.awt.image包下的

Toolkit.getDefaultToolkit().createImage(Url)
Toolkit.getDefaultToolkit().createImage(File);

返回是java.awt.Image

javax.imageio包下的：

ImageIO.read(Url)；

返回是BufferedImage

2. Image to bytes;

   Iterator iter  =  ImageIO.getImageWritersByMIMEType( " image/jpeg " );
            ImageWriter writer  =  iter.hasNext()  ?  (ImageWriter) iter.next() :  null ;
            ByteArrayOutputStream baos  =   new  ByteArrayOutputStream();
            ImageOutputStream ios  =  ImageIO.createImageOutputStream(baos);
            writer.setOutput(ios);
            BufferedImage rendImage  =   null ;
             if  (image  instanceof  BufferedImage)  {
                rendImage = (BufferedImage) image;
            }   else   {
                Frame frame = new Frame();
                frame.addNotify();
                MediaTracker tracker = new MediaTracker(frame);                
                tracker.addImage(image, 0);
                tracker.waitForAll();
                rendImage = new BufferedImage(image.getWidth(null),
                        image.getHeight(null), 1);
                Graphics g = rendImage.createGraphics();
                g.drawImage(image, 0, 0, null);
            }
            writer.write( new  IIOImage(rendImage,  null ,  null ));
            writer.dispose();
             return  baos.toByteArray();

3. 剪裁图片
起作用是ImageFilter

    ImageFilter smallCropFilter  = new  CropImageFilter( 0 , 0 , 20 , 20 );
    java.awt.Image smallImage =  Toolkit.getDefaultToolkit().createImage( new  FilteredImageSource(sourceImage.getSource(),smallCropFilter));