Re: How to have a RenderedDynamicImageResource with transparent background?

[Michael O'Cleirigh <mi...@rivulet.ca>]

Hi Reinhard,

You need to seperate your image generating logic from the wicket Image 
Resource. 

I'd create a test program or unit test to build verify that the image 
you want is being built correctly and then bind it into wicket.

For example you can just use a BufferedDynamicImageResource with the 
image you generate.

Here is some code I have for writing a string into an image.  If you 
pass backgroundColor = null it will emit a transparent background with 
foregroundColor text on top.

public static BufferedImage writeString(String text, int height, int 
width, Font font, Color backgroundColor, Color foregroundColor) {
       
         // TYPE_INT_ARGB specifies the image format: 8-bit RGBA packed
          // into integer pixels
          BufferedImage bi = new BufferedImage(width, height, 
BufferedImage.TYPE_INT_ARGB);

          Graphics2D graphics2D = bi.createGraphics();


        
          graphics2D.setFont(font);
          FontMetrics fontMetrics = graphics2D.getFontMetrics();
          int stringWidth = fontMetrics.stringWidth(text);
          int stringHeight = fontMetrics.getAscent();
         
          if (backgroundColor != null) {
              graphics2D.setBackground(backgroundColor);
         
              graphics2D.clearRect(0, 0, width, height);
             
          }
         
          graphics2D.setPaint(foregroundColor);
         
          graphics2D.drawString(text, (width - stringWidth) / 2, height 
/ 2 + stringHeight / 4);
         
          return bi;
    }

These Wiki references that should also help you:

http://cwiki.apache.org/WICKET/how-to-create-dynamic-image-overlays.html
http://cwiki.apache.org/WICKET/how-to-stamp-an-image-template-with-context-specific-details.html

Regards,

Mike
> I like to have a RenderedDynamicImageResource with a transparent background.
> I tried serveral things google came up with. But none worked so far.
> Let me show you what I do:
>
>         public RenderedDynamicImageResource getCity(final Long cityId){
>                 RenderedDynamicImageResource image = new
> RenderedDynamicImageResource(500, 570) {
>                     private static final long serialVersionUID = 1L;
>
>                     @Override
>                     protected boolean render(Graphics2D mapGraphic) {
>                         return renderCity(mapGraphic, cityId);
>                     }
>                 };
>
>                 return image;
>             }
>
>
>     protected boolean renderCity(Graphics2D mapGraphic, final Long cityId) {
>
>            ....
>
>             // Prepare g2 for transparency
>           //one of the approches I tried... without luck
>
>
> mapGraphic.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC,
> 0.9f));
>             Rectangle2D.Double rect = new Rectangle2D.Double(0, 0, 500,
>                     570);
>             mapGraphic.fill(rect);
>
>            .....
>
>           // Here I draw some shapes into the mapGraphic
>
>            ....
>
>          //in the end I'd like to have a png with a transparent  background
> and some shapes on it
>     }
>
>
>
> If anyone can provide me with help or even a working example, that would be
> greatly apreciated.
>
> cheers
> reinhard
>
>   


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