AreaAveragingScaleFilter (Java SE 26 & JDK 26)
Description: declaration: module: java.desktop, package: java.awt.image, class: AreaAveragingScaleFilter
Keywords: java.awt.image.AreaAveragingScaleFilter class

# Class AreaAveragingScaleFilter

java.lang.Object
java.awt.image.ImageFilter
java.awt.image.ReplicateScaleFilter
java.awt.image.AreaAveragingScaleFilter

All Implemented Interfaces:
  `ImageConsumer, Cloneable`

public class AreaAveragingScaleFilter extends ReplicateScaleFilter
An ImageFilter class for scaling images using a simple area averaging algorithm that produces smoother results than the nearest neighbor algorithm.

This class extends the basic ImageFilter Class to scale an existing image and provide a source for a new image containing the resampled image. The pixels in the source image are blended to produce pixels for an image of the specified size. The blending process is analogous to scaling up the source image to a multiple of the destination size using pixel replication and then scaling it back down to the destination size by simply averaging all the pixels in the supersized image that fall within a given pixel of the destination image. If the data from the source is not delivered in TopDownLeftRight order then the filter will back off to a simple pixel replication behavior and utilize the requestTopDownLeftRightResend() method to refilter the pixels in a better way at the end.

It is meant to be used in conjunction with a FilteredImageSource object to produce scaled versions of existing images. Due to implementation dependencies, there may be differences in pixel values of an image filtered on different platforms.

See Also:
  - `FilteredImageSource`
  - `ReplicateScaleFilter`
  - `ImageFilter`

- ## Field Summary

  ### Fields declared in class ReplicateScaleFilter

  `destHeight, destWidth, outpixbuf, srccols, srcHeight, srcrows, srcWidth`
  Modifier and Type
  Field
  Description
  `protected int`
  `destHeight`
  The target height to scale the image.
  `protected int`
  `destWidth`
  The target width to scale the image.
  `protected Object`
  `outpixbuf`
  A `byte` array initialized with a size of `ReplicateScaleFilter.destWidth` and used to deliver a row of pixel data to the `ImageConsumer`.
  `protected int[]`
  `srccols`
  An `int` array containing information about a column of pixels.
  `protected int`
  `srcHeight`
  The height of the source image.
  `protected int[]`
  `srcrows`
  An `int` array containing information about a row of pixels.
  `protected int`
  `srcWidth`
  The width of the source image.

  ### Fields declared in class ImageFilter

  `consumer`
  Modifier and Type
  Field
  Description
  `protected ImageConsumer`
  `consumer`
  The consumer of the particular image data stream for which this instance of the ImageFilter is filtering data.

  ### Fields declared in interface ImageConsumer

  `COMPLETESCANLINES, IMAGEABORTED, IMAGEERROR, RANDOMPIXELORDER, SINGLEFRAME, SINGLEFRAMEDONE, SINGLEPASS, STATICIMAGEDONE, TOPDOWNLEFTRIGHT`
  Modifier and Type
  Field
  Description
  `static final int`
  `COMPLETESCANLINES`
  The pixels will be delivered in (multiples of) complete scanlines at a time.
  `static final int`
  `IMAGEABORTED`
  The image creation process was deliberately aborted.
  `static final int`
  `IMAGEERROR`
  An error was encountered while producing the image.
  `static final int`
  `RANDOMPIXELORDER`
  The pixels will be delivered in a random order.
  `static final int`
  `SINGLEFRAME`
  The image contain a single static image.
  `static final int`
  `SINGLEFRAMEDONE`
  One frame of the image is complete but there are more frames to be delivered.
  `static final int`
  `SINGLEPASS`
  The pixels will be delivered in a single pass.
  `static final int`
  `STATICIMAGEDONE`
  The image is complete and there are no more pixels or frames to be delivered.
  `static final int`
  `TOPDOWNLEFTRIGHT`
  The pixels will be delivered in top-down, left-to-right order.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `AreaAveragingScaleFilter(int width, int height)`
  Constructs an AreaAveragingScaleFilter that scales the pixels from its source Image as specified by the width and height parameters.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `setHints(int hints)`
  Detect if the data is being delivered with the necessary hints to allow the averaging algorithm to do its work.
  `void`
  `setPixels(int x, int y, int w, int h, ColorModel model, byte[] pixels, int off, int scansize)`
  Combine the components for the delivered byte pixels into the accumulation arrays and send on any averaged data for rows of pixels that are complete.
  `void`
  `setPixels(int x, int y, int w, int h, ColorModel model, int[] pixels, int off, int scansize)`
  Combine the components for the delivered int pixels into the accumulation arrays and send on any averaged data for rows of pixels that are complete.

  ### Methods declared in class ReplicateScaleFilter

  `setDimensions, setProperties`
  Modifier and Type
  Method
  Description
  `void`
  `setDimensions(int w, int h)`
  Override the dimensions of the source image and pass the dimensions of the new scaled size to the ImageConsumer.
  `void`
  `setProperties(Hashtable<?,?> props)`
  Passes along the properties from the source object after adding a property indicating the scale applied.

  ### Methods declared in class ImageFilter

  `clone, getFilterInstance, imageComplete, resendTopDownLeftRight, setColorModel`
  Modifier and Type
  Method
  Description
  `Object`
  `clone()`
  Clones this object.
  `ImageFilter`
  `getFilterInstance(ImageConsumer ic)`
  Returns a unique instance of an ImageFilter object which will actually perform the filtering for the specified ImageConsumer.
  `void`
  `imageComplete(int status)`
  Filters the information provided in the imageComplete method of the ImageConsumer interface.
  `void`
  `resendTopDownLeftRight(ImageProducer ip)`
  Responds to a request for a TopDownLeftRight (TDLR) ordered resend of the pixel data from an `ImageConsumer`.
  `void`
  `setColorModel(ColorModel model)`
  Filter the information provided in the setColorModel method of the ImageConsumer interface.

  ### Methods declared in class Object

  `equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object obj)`
  Indicates whether some other object is "equal to" this one.
  `protected void`
  `finalize()`
  Deprecated, for removal: This API element is subject to removal in a future version.
  Finalization is deprecated and subject to removal in a future release.
  `final Class<?>`
  `getClass()`
  Returns the runtime class of this `Object`.
  `int`
  `hashCode()`
  Returns a hash code value for this object.
  `final void`
  `notify()`
  Wakes up a single thread that is waiting on this object's monitor.
  `final void`
  `notifyAll()`
  Wakes up all threads that are waiting on this object's monitor.
  `String`
  `toString()`
  Returns a string representation of the object.
  `final void`
  `wait()`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
  `final void`
  `wait(long timeoutMillis)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
  `final void`
  `wait(long timeoutMillis, int nanos)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

- ## Constructor Details

  - ### AreaAveragingScaleFilter

    public AreaAveragingScaleFilter(int width, int height)
    Constructs an AreaAveragingScaleFilter that scales the pixels from its source Image as specified by the width and height parameters.
    Parameters:
      `width` - the target width to scale the image
      `height` - the target height to scale the image
    Throws:
      `IllegalArgumentException` - if `width` equals zero or `height` equals zero

- ## Method Details

  - ### setHints

    public void setHints(int hints)
    Detect if the data is being delivered with the necessary hints to allow the averaging algorithm to do its work.

    Note: This method is intended to be called by the `ImageProducer` of the `Image` whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation.

    Specified by:
      `setHints` in interface `ImageConsumer`
    Overrides:
      `setHints` in class `ImageFilter`
    Parameters:
      `hints` - a set of hints that the ImageConsumer uses to process the pixels
    See Also:
      - `ImageConsumer.setHints(int)`

  - ### setPixels

    public void setPixels(int x, int y, int w, int h, ColorModel model, byte[] pixels, int off, int scansize)
    Combine the components for the delivered byte pixels into the accumulation arrays and send on any averaged data for rows of pixels that are complete. If the correct hints were not specified in the setHints call then relay the work to our superclass which is capable of scaling pixels regardless of the delivery hints.

    Note: This method is intended to be called by the `ImageProducer` of the `Image` whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation.

    Specified by:
      `setPixels` in interface `ImageConsumer`
    Overrides:
      `setPixels` in class `ReplicateScaleFilter`
    Parameters:
      `x` - the X coordinate of the upper-left corner of the area of pixels to be set
      `y` - the Y coordinate of the upper-left corner of the area of pixels to be set
      `w` - the width of the area of pixels
      `h` - the height of the area of pixels
      `model` - the specified `ColorModel`
      `pixels` - the array of pixels
      `off` - the offset into the `pixels` array
      `scansize` - the distance from one row of pixels to the next in the `pixels` array
    See Also:
      - `ReplicateScaleFilter`

  - ### setPixels

    public void setPixels(int x, int y, int w, int h, ColorModel model, int[] pixels, int off, int scansize)
    Combine the components for the delivered int pixels into the accumulation arrays and send on any averaged data for rows of pixels that are complete. If the correct hints were not specified in the setHints call then relay the work to our superclass which is capable of scaling pixels regardless of the delivery hints.

    Note: This method is intended to be called by the `ImageProducer` of the `Image` whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation.

    Specified by:
      `setPixels` in interface `ImageConsumer`
    Overrides:
      `setPixels` in class `ReplicateScaleFilter`
    Parameters:
      `x` - the X coordinate of the upper-left corner of the area of pixels to be set
      `y` - the Y coordinate of the upper-left corner of the area of pixels to be set
      `w` - the width of the area of pixels
      `h` - the height of the area of pixels
      `model` - the specified `ColorModel`
      `pixels` - the array of pixels
      `off` - the offset into the `pixels` array
      `scansize` - the distance from one row of pixels to the next in the `pixels` array
    See Also:
      - `ReplicateScaleFilter`