javax.media.jai.operator
Class DilateDescriptor

java.lang.Object
  |
  +--javax.media.jai.OperationDescriptorImpl
        |
        +--javax.media.jai.operator.DilateDescriptor

All Implemented Interfaces:

OperationDescriptor, RegistryElementDescriptor, Serializable

public class DilateDescriptor

extends OperationDescriptorImpl

An OperationDescriptor describing the "Dilate" operation. Dilation for gray scale images can be charaterized by "slide, add and max", while for binary images by "slide and set". As always, the kernel is expected to come with a key position.

Dilation, unlike convolution and most neighborhood operations, actually can grow the image region. But to conform with other image neighborhood operations, the border pixels are set to 0. For a 3 x 3 kernel with the key point at the center, there will be a pixel wide 0 stripe around the border.

When applied to multi-band images the dilation operator processes each band independently using the methodology which would be applied to single band images of the same data type.

Gray scale dilation is a spatial operation that computes each output sample by adding elements of a kernel to the samples surrounding a particular source sample and taking the maximum. A mathematical expression is:

For a kernel K with a key position (xKey,yKey), the dilation of image I at (x,y) is given by:

     max{ I(x-i, y-j) + K(xKey+i, yKey+j): some (i,j) restriction }
  
      where the (i,j) restriction means:
      all possible (i,j) so that both I(x-i,y-j) and K(xKey+i, yKey+j)
      are defined, that is, these indices are in bounds.

 

Intuitively in 2D, the kernel is like an umbrella and the key point is the handle. When the handle moves all over the image surface, the upper outbounds of all the umbrella positions is the dilation. Thus if you want the image to dilate in the upper right direction, the following kernel would do with the bold face key position.

0	0	50
0	50	0
0	0	0

Note also that zero kernel have effects on the dilation! That is because of the "max" in the add and max process. Thus a 3 x 1 zero kernel with the key position at the bottom of the kernel dilates the image upwards.

After the kernel is rotated 180 degrees, Pseudo code for dilation operation is as follows. Of course, you should provide the kernel in its (unrotated) original form. Assuming the kernel K is of size M rows x N cols and the key position is (xKey, yKey).

 // gray-scale dilation:
 for every dst pixel location (x,y){
    dst[x][y] = -infinity;
    for (i = -xKey; i < M - xKey; i++){
       for (j = -yKey; j < N - yKey; j++){
          if((x+i, y+j) are in bounds of src &&
	      (xKey+i, yKey+j) are in bounds of K){
             tmp = src[x + i][y + j]+ K[xKey + i][yKey + j];
	       dst[x][y] = max{tmp, dst[x][y]};
          }
       }
    }
 }
 

The kernel cannot be bigger in any dimension than the image data.

Binary Image Dilation requires the kernel K to be binary, that is, have values 0 or 1 for all kernel entries. Intuitively, starting from dst image being a duplicate of src, binary dilation slides the kernel K to place the key position at every non-zero point (x,y) in src image and set dst positions under ones of K to 1.

After the kernel is rotated 180 degrees, the pseudo code for dilation operation is as follows. (Of course, you should provide the kernel in its original unrotated form.)

 
 // binary dilation
 for every dst pixel location (x,y){
    dst[x][y] = src[x][y];
    for (i = -xKey; i < M - xKey; i++){
       for (j = -yKey; j < N - yKey; j++){
         if(src[x+i,y+i]==1 && Key(xKey+i, yKey+j)==1){
            dst[x][y] = 1; break;
          }
       }
    }
 }

 

 
Resource List
 
Name
        
Value
 
GlobalName
  
Dilate
 
LocalName
   
Dilate
 
Vendor
      
com.sun.media.jai
 
Description
 
Performs kernel based Dilate on
                              an image.
 
DocURL
      
http://java.sun.com/products/java-media/jai/forD
evelopers/jai-apidocs/javax/media/jai/operator/DilateDescriptor.html
 
Version
     
1.1
 
arg0Desc
    
The dilate kernel.
 

 

 
Parameter List
 
Name
          
Class Type
                            
Default Value
 
kernel
        
javax.media.jai.KernelJAI
                            
NO_PARAMETER_DEFAULT
 

 

Reference: An Introduction to Nonlinear Image Processing, by Edward R. Bougherty and Jaakko Astola, Spie Optical Engineering Press, 1994.

Since:

JAI 1.1

See Also:

OperationDescriptor, KernelJAI, ErodeDescriptor, Serialized Form

Fields inherited from class javax.media.jai.OperationDescriptorImpl

resources, sourceNames, supportedModes

Constructor Summary

DilateDescriptor()
Constructor.

Method Summary

PropertyGenerator[]

getPropertyGenerators() Returns an array of PropertyGenerators implementing property inheritance for the "Dilate" operation.

Methods inherited from class javax.media.jai.OperationDescriptorImpl

arePropertiesSupported, getDefaultSourceClass, getDestClass, getDestClass, getInvalidRegion, getName, getNumParameters, getNumSources, getParamClasses, getParamDefaults, getParamDefaultValue, getParameterListDescriptor, getParamMaxValue, getParamMinValue, getParamNames, getPropertyGenerators, getRenderableDestClass, getRenderableSourceClasses, getResourceBundle, getResources, getSourceClasses, getSourceClasses, getSourceNames, getSupportedModes, isImmediate, isModeSupported, isRenderableSupported, isRenderedSupported, makeDefaultSourceClassList, validateArguments, validateArguments, validateParameters, validateParameters, validateRenderableArguments, validateRenderableSources, validateSources, validateSources

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DilateDescriptor

public DilateDescriptor()

Constructor.

Method Detail

getPropertyGenerators

public PropertyGenerator[] getPropertyGenerators()

Returns an array of PropertyGenerators implementing property inheritance for the "Dilate" operation.

Overrides:

getPropertyGenerators in class OperationDescriptorImpl

Returns:

An array of property generators.