Java(TM) Boutique - Using Rasters for Image Processing, Part 1

Tutorials : Using Rasters for Image Processing, Part 1 :

Creating a SampleModel Object

As noted earlier, because the SampleModel class is an abstract class, you can't create direct instances of it. This is why, in order to get a SampleModel object, you create instances of one of its subclasses: ComponentSampleModel, PixelInterleavedSampleModel, BandedSampleModel, SinglePixelPackedSampleModel, or MultiPixelPackedSampleModel. This article's example uses SinglePixelPackedSampleModel. The constructors of this class are:

public SinglePixelPackedSampleModel(int data_type, int w, int h, int[] bit_masks): This creates a SinglePixelPackedSampleModel object that you can use for storing all samples of a pixel in one data buffer element. The three arguments represent:
1. data_type: This represents the data type used for storing samples (DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT sau DataBuffer.TYPE_INT);
2. w,h: This represents the width and height of the region of the image that is processed.
3. bit_masks: This represents the bit masks for all the image bands and is used for storing and extracting samples. For example, the ARGB color model has four bit masks—one bit mask for every band. Bit masks are contagious and do not overlap. Every sample is stored in the corresponding data buffer element starting from a given position. The position depends on the sample bit mask. The number of bit masks is the same as the number of image bands. This affirmation is mutual.

public SinglePixelPackedSampleModel(int data_type, int w, int h, int scanline_stride , int[] bit_masks): As you can see, this constructor is almost identical with the one above. The difference is that this constructor specifies the scanline stride. You can locate the index of a (x,y) pixel into the data buffer using the following formula:


index = (y*scanline_stride+x)

The following code is an example of creating a DataBufferInt and a SinglePixelPackedSampleModel:


Image IMG=null;
int pixels[];
int W,H;
�
W=IMG.getWidth(this)/3;
H=IMG.getHeight(this)/3;
pixels=new int[W*H];
�
PixelGrabber PG=new PixelGrabber(IMG,0,0,W,H,pixels,0,W);
     try{
         PG.grabPixels();
         }catch(InterruptedException e)
            {System.out.println(e.getMessage());}
�
//DataBuffer
DataBufferInt DB=new DataBufferInt(pixels,(W*H),0);
           
//SampleModel 
//this bit masks coresponding to the default color model
int[] BM=new int[]{0xff0000,0xff00,0xff,0xff000000};
SinglePixelPackedSampleModel SM=new
SinglePixelPackedSampleModel(DataBuffer.TYPE_INT,W,H,BM);
�

Note that the PixelGrabber class is used for extracting pixels from an image. For a good presentation of this class, take a look at this site.

Methods for Bit Masks

To retrieve bit masks, use public int[] getBitMasks():


int[] getBM=SM.getBitMasks();
for(int i=0;i<getBM.length;i++)
     System.out.println("getBM["+i+"]="+getBM[i]);

To retrieve the number of bits per sample for all bands, use public int[] getSampleSize():


int[] bits_per_sample=SM.getSampleSize();
          for(int i=0;i<bit_per_sample.length;i++)
		  System.out.println("Bit/sample["+i+"]="+bit_per_sample[i]);

To retrive the number of bits per sample for a specified band use public int getSampleSize(int band):


int bits_per_sample_band_2=SM.getSampleSize(2);
           System.out.println
		   ("For the second band we have "+bits_per_sample_band_2+"
		   bits/sample.");

To retrive the bit offsets use public int[] getBitOffsets():


int[] bit_offsets=SM.getBitOffsets();
               for(int i=0;i<bit_offsets.length;i++)
                   System.out.println("bit_offsets["+i+"]="+t[i]);

Home / Articles / Using Rasters for Image Processing, Part 1 / 1 / 2 / 3 /

Applet Index
(sorted alphabetically)
A B C D E F G H I J K
L M N O P Q R S T U
V W X Y Z #s

The Java Source
(applets w/source code)
A B C D E F G H I J K
L M N O P Q R S T U
V W X Y Z

How to Add Java Applets to Your Site

New on the Java Boutique:

New Review:

Time Management Made Easy with the Quartz Enterprise Job Scheduler
Why not just use the Java timer API? This open source scheduling API boasts simplicity, ease-of-integration, a well-rounded feature set, and it's free!

New Applet:

Reverse Complement
Reverse Complement is a simple applet that converts DNA or RNA sequences into three useful formats.