echopoint.image
Class EncodedImageReference

java.lang.Object
  nextapp.echo.AbstractImageReference
      nextapp.echo.StreamImageReference
          echopoint.image.EncodedImageReference

All Implemented Interfaces:

java.io.Serializable, ImageReference

Direct Known Subclasses:

TextImageReference

public class EncodedImageReference
extends StreamImageReference
implements java.io.Serializable

The EncodedImageReference class is an ImageReference that can render java.awt.Image objects. The ImageEncoder used to encode the image data is pluggable.

This class allows you to balance memory usage versus processor usage.

By default the output of the encoding is not kept in memory, so the encoding runs every time the image needs to be rendered. However this can be changed so that the encoding results are kept in memory.

If the image data is cached, they are kept in a SoftReference so they may be reclaimed by the GC if memory gets low.

The AWT Image object that is renderered is by default kept in memory. You can change this by deriving a new class from EncodedImageReference and then drawing the AWT image on as needed basis during the call to getImage().

See Also:

Serialized Form

Field Summary

Fields inherited from class nextapp.echo.AbstractImageReference

listenerList

Fields inherited from interface nextapp.echo.ImageReference

SIZE_UNKNOWN

Constructor Summary

EncodedImageReference()
Constructs an EncodedImageReference without an image.

EncodedImageReference(java.awt.Image image)
Constructs an EncodedImageReference with an image.

Method Summary

java.lang.String	getContentType() Returns the valid RFC 1521 image content type (image/png, image/jpeg, image/gif, etc) of the image.
ImageEncoder	getEncoder() Returns the ImageEncoder in use.
int	getHeight() This returns the height of the Image
java.awt.Image	getImage() Returns the Image in use.
int	getWidth() This returns the width of the Image
boolean	isKeptInMemory() Returns true if the encoded image is cached in memory.
boolean	isValid() This returns whether the AWT Image data is currently valid.
void	render(java.io.OutputStream out) Sends a byte representation of the image in its native format out the given output stream.
void	setEncoder(ImageEncoder encoder) Sets the ImageEncoder to use for encoding
void	setImage(java.awt.Image image) Sets the Image to encode.
void	setKeptInMemory(boolean b) If set to true, the image will be encoded only as necessary and then cached in memory, otherwise it will be encoded as required.
void	setValid(boolean valid) This controls whether the AWT Image data is currently valid.
void	update() Notifies listeners that the referenced image has changed.

Methods inherited from class nextapp.echo.AbstractImageReference

addImageUpdateListener, removeImageUpdateListener

Methods inherited from class java.lang.Object

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

Constructor Detail

EncodedImageReference

public EncodedImageReference()

Constructs an EncodedImageReference without an image. You must of course call setImage() before the image is rendered, otherwise there will be nothing to render.

Another alternative would be to derive a new class and override getImage() to provide the image as necessary. This will use a smallest amount of memory at the expense of more CPU processing.

EncodedImageReference

public EncodedImageReference(java.awt.Image image)

Constructs an EncodedImageReference with an image.

Parameters:

image - A java.awt.Image to be displayed. If you intend to extend this class and override the getImage() method to return images only as they are needed, then you may pass null to this parameter.

Method Detail

getContentType

public java.lang.String getContentType()

Description copied from class: StreamImageReference

Returns the valid RFC 1521 image content type (image/png, image/jpeg, image/gif, etc) of the image.

Specified by:

getContentType in class StreamImageReference

Returns:

The content type of the image.

See Also:

StreamImageReference.getContentType()

getEncoder

public ImageEncoder getEncoder()

Returns the ImageEncoder in use.

Returns:

ImageEncoder

getHeight

public int getHeight()

This returns the height of the Image

Specified by:

getHeight in interface ImageReference

Overrides:

getHeight in class StreamImageReference

Returns:

The height of the image in pixels.

See Also:

ImageReference.getHeight()

getImage

public java.awt.Image getImage()

Returns the Image in use.

You may extend this class and override this method such that images are created only when they are needed, thereby reducing memory usage at the cost of increased processor workload.

Returns:

Image - the AWT image object

getWidth

public int getWidth()

This returns the width of the Image

Specified by:

getWidth in interface ImageReference

Overrides:

getWidth in class StreamImageReference

Returns:

The width of the image in pixels.

See Also:

ImageReference.getWidth()

isKeptInMemory

public boolean isKeptInMemory()

Returns true if the encoded image is cached in memory.

Returns:

boolean true if the image is kept in memory

isValid

public boolean isValid()

This returns whether the AWT Image data is currently valid.

Returns:

- true if the AWT image is valid

render

public void render(java.io.OutputStream out)
            throws java.io.IOException

Description copied from class: StreamImageReference

Sends a byte representation of the image in its native format out the given output stream.

Specified by:

render in class StreamImageReference

Parameters:

out - The output stream to write the image.

Throws:

java.io.IOException

See Also:

StreamImageReference.render(java.io.OutputStream)

setEncoder

public void setEncoder(ImageEncoder encoder)

Sets the ImageEncoder to use for encoding

Parameters:

encoder -

setImage

public void setImage(java.awt.Image image)

Sets the Image to encode. This can be null.

Parameters:

image - - the AWT Image to encode.

setKeptInMemory

public void setKeptInMemory(boolean b)

If set to true, the image will be encoded only as necessary and then cached in memory, otherwise it will be encoded as required.

Parameters:

b -

setValid

public void setValid(boolean valid)

This controls whether the AWT Image data is currently valid.

This is used to determine whether a call to getImage() should be made. If the encoded image is kept in memory but the image is invalid, then it will be encoded again. If it valid, then the cached encoded image data can be re-used.

If you derive a new class and override the getImage() method, you should set this to false when the image needs to be re-painted.

Parameters:

valid - - true if the AWT image data is valid.

update

public void update()

Description copied from interface: ImageReference

Notifies listeners that the referenced image has changed.

Specified by:

update in interface ImageReference

Overrides:

update in class AbstractImageReference

See Also:

ImageReference.update()