javax.media.jai.operator
Class ErodeDescriptor

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

All Implemented Interfaces:

OperationDescriptor, RegistryElementDescriptor, Serializable

public class ErodeDescriptor

extends OperationDescriptorImpl

An OperationDescriptor describing the "Erode" operation.

Gray Scale Erosion is a spatial operation that computes each output sample by subtracting elements of a kernel from the samples surrounding a particular source sample. The mathematical formulation for erosion operation is:

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

     max{ f:  f + K(xKey+i, yKey+j) <= I(x+i,y+j): all (i,j)}

      "all" possible (i,j) means that both I(x+i,y+j) and K(xKey+i, yKey+j)
      are in bounds. Otherwise, the value is set to 0.
      "f" represents all possible floats satisfying the restriction.

 

Intuitively, the kernel is like an unbrella and the key point is the handle. At every point, you try to push the umbrella up as high as possible but still underneath the image surface. The final height of the handle is the value after erosion. Thus if you want the image to erode from the upper right to bottom left, the following would do.

0	0	X
0	X	0
X	0	0

Note that even if every entry of a kernel is zero, the erosion changes the image. Different key positions will also lead to different erosion results for such zero kernels.

Pseudo code for the erosion operation is as follows. Assuming the kernel K is of size M rows x N cols and the key position is (xKey, yKey).

 
 // erosion
 for every dst pixel location (x,y){
    tmp = 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){
             tmp = min{tmp, src[x + i][y + j] - K[xKey + i][yKey + j]};
          }
       }
    }
    dst[x][y] = tmp;
    if (dst[x][y] == infinity)
        dst[x][y] = 0;
 }
 

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

Binary Image Erosion requires the kernel to be binary, that is, to have values 0 and 1 for each kernel entry. Intuitively, binary erosion slides the kernel key position and place it at every point (x,y) in the src image. The dst value at this position is set to 1 if the entire kernel lies within the image bounds and the src image value is 1 wherever the corresponding kernel value is 1." Otherwise, the value after erosion at (x,y) is set to 0. Erosion usually shrinks images, but it can fill holes with kernels like

 [1 0 1] 

and the key position at the center.

Pseudo code for the binary erosion operation is as follows.

 // erosion
 for every dst pixel location (x,y){
    dst[x][y] = 1;
    for (i = -xKey; i < M - xKey; i++){
       for (j = -yKey; j < N - yKey; j++){
         if((x+i,y+j) is out of bounds of src ||
             src(x+i, y+j)==0 && Key(xKey+i, yKey+j)==1){
            dst[x][y] = 0; break;
          }
       }
    }
 }

 See the following listed references for the underlying
 connection between these to algorithms.

 

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

KernelJAI, Serialized Form

Fields inherited from class javax.media.jai.OperationDescriptorImpl

resources, sourceNames, supportedModes

Constructor Summary

ErodeDescriptor()
Constructor.

Method Summary

PropertyGenerator[]

getPropertyGenerators() Returns an array of PropertyGenerators implementing property inheritance for the "Erode" 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

ErodeDescriptor

public ErodeDescriptor()

Constructor.

Method Detail

getPropertyGenerators

public PropertyGenerator[] getPropertyGenerators()

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

Overrides:

getPropertyGenerators in class OperationDescriptorImpl

Returns:

An array of property generators.