Package ca.cgjennings.graphics.filters

Class AbstractImagewiseFilter

java.lang.Object

ca.cgjennings.graphics.filters.AbstractImageFilter

ca.cgjennings.graphics.filters.AbstractImagewiseFilter

All Implemented Interfaces:

java.awt.image.BufferedImageOp

Direct Known Subclasses:

AbstractConvolver, OilPaintingFilter

public abstract class AbstractImagewiseFilter
extends AbstractImageFilter

An abstract base class for image filters that require access to the entire image at once when processing. Filters of this type produce images of the same dimensions as the original.

It is assumed that pixels will only be read from the source image and written to the destination image. That is, that pixel values depend only on combinations of the source pixels and not on previously computed destination pixels. This allows filtering to be accelerated automatically by generating blocks of destination pixels in parallel. A filter that does not meet these criteria may return a value of 0 from workFactor() to disable the automatic acceleration mechanism.

Author:

Chris Jennings

Constructor Summary

Constructors

Constructor	Description
AbstractImagewiseFilter()

Method Summary

Modifier and Type	Method	Description
int[]	filter(int[] source, int[] destination, int width, int height)	Applies the filter to ARGB pixel data stored in an array.
java.awt.image.BufferedImage	filter(java.awt.image.BufferedImage source, java.awt.image.BufferedImage destination)
protected abstract void	filterPixels(int[] srcPixels, int[] dstPixels, int width, int height, int y0, int rows)	Filters a block of rows in the source image, placing the result in the corresponding rows in the destination image.
protected float	workFactor()	Returns a factor representing the amount of work performed by this filter relative to a filter that simply copies the source image by reading and writing each pixel.

Methods inherited from class ca.cgjennings.graphics.filters.AbstractImageFilter

clamp, clamp, clamp, clampBoth, createCompatibleDestImage, fA, fB, fG, fR, getARGB, getARGB, getARGBSynch, getBounds2D, getPoint2D, getRenderingHints, iA, iB, iG, iR, setARGB, setARGB, setARGBSynch

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractImagewiseFilter

public AbstractImagewiseFilter()

Method Detail

filter

public java.awt.image.BufferedImage filter(java.awt.image.BufferedImage source,
                                           java.awt.image.BufferedImage destination)

This implementation will call filterPixels(int[], int[], int, int, int, int) to perform the actual filtering.

Parameters:

source - the source image

destination - the destination image (may be null)

Returns:

the destination image

filter

public int[] filter(int[] source,
                    int[] destination,
                    int width,
                    int height)

Applies the filter to ARGB pixel data stored in an array. This method can be used during the internal processing of other filters.

Parameters:

source - the source pixel data in ARGB format

destination - the destination in which the filtered should be stored, may be null

width - the width of the source image

height - the height of the source image

Returns:

the array that holds the destination pixels

filterPixels

protected abstract void filterPixels(int[] srcPixels,
                                     int[] dstPixels,
                                     int width,
                                     int height,
                                     int y0,
                                     int rows)

Filters a block of rows in the source image, placing the result in the corresponding rows in the destination image. The block of rows to be filtered runs from y0 to y0 + rows-1 (inclusive).

Parameters:

srcPixels - the pixel data for the source image

dstPixels - the destination for output pixels

width - the width of the image

height - the height of the image

y0 - the index of the first row to filter

rows - the number of rows to filter

workFactor

protected float workFactor()

Returns a factor representing the amount of work performed by this filter relative to a filter that simply copies the source image by reading and writing each pixel. For example, a filter that implemented a 3x3 convolution might return the value 9. The work factor value helps determine when an image should be processed in parallel. (There is significant overhead involved in running a filter in parallel, so it is only worth doing if the image is relatively large or the amount of processing per pixel is relatively high.)

Note: The work factor may vary depending on the current filter settings.

Returns:

the approximate amount of work per pixel, relative to simply copying the pixel values