Scaling Images

asked 2008-09-19 18:45:15 +0800

ansancle gravatar image ansancle
317 9

This post isn't necessarily entirely about ZK, but does anyone have any sample code of taking a byte[] that represents an image and then being able to scale it into a ZK image of a different size?
For example, a 128px wide and 128px high image is read from the db, I want to scale it down to 32x32.

I know how to create a java.awt.Image, BufferedImage, and then a ZK Image and have tried several things from examples on the web, just doesn't work. I get a black box of the correct size but no image.

Here is what I had tried :

	public org.zkoss.zul.Image scaleImage(byte[] imageBlob,int width,int height)
		ImageObserver observer = null;
		java.awt.Image image = Toolkit.getDefaultToolkit().createImage(imageBlob);		
		java.awt.Image scaledImage = image.getScaledInstance(width, height, java.awt.Image.SCALE_SMOOTH);
		BufferedImage bufferedImage = new BufferedImage ( width,
									  BufferedImage.SCALE_SMOOTH  );
		Graphics2D graphics = bufferedImage.createGraphics();
		graphics.drawImage( scaledImage, 0, 0, observer);
		org.zkoss.zul.Image zkImage = new org.zkoss.zul.Image();
		return zkImage;

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answered 2008-09-20 16:34:11 +0800

dennis gravatar image dennis
3669 1 6

Did you read javadoc ? http://www.potix.com/javadoc/
I don't think zkImage.setContent can accept BufferedIamge, the argument must be a org.zkoss.image.Image .
try to warp the byte[] of bufferedImage with AImage object , and use AImage as argument of Image.setContent


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answered 2008-09-22 16:01:15 +0800

ansancle gravatar image ansancle
317 9

I found the solution to scaling images, the following sample code handles the task. Of course this could be rewritten into one clean method but I was just testing different things and happen to get it to work and wanted to post it up here.

	 public BufferedImage getImage(byte[] data) throws Exception
	    BufferedImage bi = null;
	    ByteArrayInputStream bais = new ByteArrayInputStream(data);
	    bi = ImageIO.read(bais);	    
	    return bi;

	public org.zkoss.zul.Image scaleImage(byte[] imageBlob,int width,int height) throws Exception
		java.awt.image.BufferedImage scaledImage = getImage(imageBlob);
		scaledImage = scaleToSize(width,height,scaledImage);
		Image zkImage = new Image();
		return zkImage;

	public BufferedImage scaleToSize(int nMaxWidth, int nMaxHeight, BufferedImage imgSrc)
	  int nHeight = imgSrc.getHeight();
	  int nWidth = imgSrc.getWidth();
	  double scaleX = (double)nMaxWidth / (double)nWidth;
	  double scaleY = (double)nMaxHeight / (double)nHeight;
	  double fScale = Math.min(scaleX, scaleY);
	  return scale(fScale, imgSrc);

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answered 2008-09-22 16:07:21 +0800

ansancle gravatar image ansancle
317 9

Here is the link that I got most of the code from :
Java Forums Image manipulation code

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Asked: 2008-09-19 18:45:15 +0800

Seen: 1,028 times

Last updated: Sep 22 '08

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