Class EncodedImage

java.lang.Object

com.codename1.ui.Image

com.codename1.ui.EncodedImage

All Implemented Interfaces:

ActionSource

Direct Known Subclasses:

ComponentImage.EncodedWrapper, FileEncodedImage, FileEncodedImageAsync, ReplaceableImage, StorageImage, StorageImageAsync, URLImage

public class EncodedImage
extends Image

EncodedImage is the workhorse of Codename One. Images returned from resource files are EncodedImage and many API's expect it.

EncodedImage is effectively an image that is "hidden" and extracted as needed to remove the memory overhead associated with loaded image. When creating an EncodedImage only the PNG (or JPEG etc.) is loaded to an array in RAM. Normally, such images are very small (relatively) so they can be kept in memory without much overhead.

When image information is needed (pixels) the image is decoded into RAM and kept in a weak/sort reference (see com.codename1.ui.Display#createSoftWeakRef(java.lang.Object)). This allows the image to be cached for performance and allows the garbage collector to reclaim it when the memory becomes scarce.

Since the fully decoded image can be pretty big (width X height X 4) the ability to store just the encoded image can be pretty stark. E.g. A standard 50x100 image will take up 20,000 bytes of RAM for a standard image but an EncodedImage can reduce that to 1kb-2kb of RAM.

When drawing an EncodedImage it checks the weak reference cache and if the image is cached then it is shown otherwise the image is loaded the encoded image cache it then drawn.

EncodedImage is not final and can be derived to produce complex image fetching strategies e.g. the com.codename1.ui.URLImage class that can dynamically download its content from the web.

EncodedImage can be instantiated via the create methods in the class. Pretty much any image can be converted into an EncodedImage via the boolean) method.

EncodedImage Locking

Naturally loading the image is more expensive so we want the images that are on the current form to remain in cache (otherwise GC will thrash a lot). That's where #lock() kicks in, when #lock() is active we keep a hard reference to the actual native image so it won't get GC'd. This significantly improves performance!

Internally this is invoked automatically for background images, icons etc. which results in a huge performance boost. This makes sense since these images are currently showing and they will be in RAM anyway. However, if you use a complex renderer or custom drawing UI you should #lock() your images where possible!

To verify that locking might be a problem you can launch the performance monitor tool (accessible from the simulator menu), if you get log messages that indicate that an unlocked image was drawn you might have a problem.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	EncodedImage(int width, int height)	Allows subclasses to create more advanced variations of this class that lazily store the data in an arbitrary location.

Method Summary

Modifier and Type	Method	Description
void	asyncLock(Image internal)	Async lock is the equivalent of a lock operation, however it uses the given image as the hard cache and performs the actual image loading asynchronously.
static EncodedImage	create(byte[] data)	Creates an image from the given byte array
static EncodedImage	create(byte[] data, int width, int height, boolean opacity)	Creates an image from the given byte array with the variables set appropriately.
static EncodedImage	create(InputStream i)	Creates an image from the input stream
static EncodedImage	create(InputStream i, int size)	Creates an image from the input stream, this version of the method is somewhat faster than the version that doesn't accept size
static EncodedImage	create(String i)	Creates an image from the input stream
static EncodedImage	createFromImage(Image i, boolean jpeg)	Converts an image to encoded image
static Image	createFromRGB(int[] argb, int width, int height, boolean jpeg)	Tries to create an encoded image from RGB which is more efficient, however if this fails it falls back to regular RGB image.
static EncodedImage	createMulti(int[] dpis, byte[][] data)	Creates an encoded image that acts as a multi-image, DO NOT USE THIS METHOD.
protected void	drawImage(Graphics g, Object nativeGraphics, int x, int y)	Callback invoked internally by Codename One to draw the image/frame onto the display.
protected void	drawImage(Graphics g, Object nativeGraphics, int x, int y, int w, int h)	Callback invoked internally by Codename One to draw the image/frame onto the display.
Graphics	getGraphics()	If this is a mutable image a graphics object allowing us to draw on it is returned.
int	getHeight()	Returns the height of the image
Object	getImage()	Returns the platform specific image implementation, warning the implementation class can change between revisions of Codename One and platforms.
byte[]	getImageData()	Returns the byte array data backing the image allowing the image to be stored and discarded completely from RAM.
protected Image	getInternal()	Returns the actual image represented by the encoded image, this image will be cached in a weak/soft reference internally.
int	getWidth()	Returns the width of the image
boolean	isAnimation()	Returns true if this is an animated image
boolean	isLocked()	Returns true if the image is locked
boolean	isOpaque()	Indicates whether this image is opaque or not
void	lock()	This callback indicates that a component pointing at this image is initialized, this allows an image to make performance sensitive considerations e.g.
Image	modifyAlpha(byte alpha)	Creates a new image instance with the alpha channel of opaque/translucent pixels within the image using the new alpha value.
Image	modifyAlpha(byte alpha, int removeColor)	Creates a new image instance with the alpha channel of opaque/translucent pixels within the image using the new alpha value.
protected void	resetCache()	A subclass might choose to load asynchroniously and reset the cache when the image is ready.
Image	rotate(int degrees)	Returns an instance of this image rotated by the given number of degrees.
void	scale(int width, int height)	Scale the image to the given width and height, this is a fast algorithm that preserves translucent information
Image	scaled(int width, int height)	Returns a scaled version of this image image using the given width and height, this is a fast algorithm that preserves translucent information.
EncodedImage	scaledEncoded(int width, int height)	Performs scaling using ImageIO to generate an encoded Image
Image	scaledHeight(int height)	Scales the image to the given height while updating the width based on the aspect ratio of the height
Image	scaledSmallerRatio(int width, int height)	Scales the image while maintaining the aspect ratio to the smaller size image
Image	scaledWidth(int width)	Scales the image to the given width while updating the height based on the aspect ratio of the width
Image	subImage(int x, int y, int width, int height, boolean processAlpha)	Extracts a subimage from the given image allowing us to breakdown a single large image into multiple smaller images in RAM, this actually creates a standalone version of the image for use.
void	toRGB(RGBImage image, int destX, int destY, int x, int y, int width, int height)	Extracts data from this image into the given RGBImage
void	unlock()	This callback indicates that a component pointing at this image is now deinitilized This method may be invoked multiple times.

Methods inherited from class Image

addActionListener, animate, applyMask, applyMask, applyMaskAutoScale, createImage, createImage, createImage, createImage, createImage, createImage, createImage, createIndexed, createMask, createSVG, dispose, exifRotation, exifRotation, exifRotation, fill, fireChangedEvent, flipHorizontally, flipVertically, getExifOrientationTag, getExifOrientationTag, getImageName, getRGB, getRGB, getRGBCached, getSVGDocument, isAlphaMutableImageSupported, isJPEG, isPNG, isSVG, isSVGSupported, mirror, modifyAlphaWithTranslucency, removeActionListener, requiresDrawImage, rotate180Degrees, rotate270Degrees, rotate90Degrees, scaledLargerRatio, setImageName

Methods inherited from class Object

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

Constructor Details

EncodedImage

protected EncodedImage(int width,
 int height)

Allows subclasses to create more advanced variations of this class that lazily store the data in an arbitrary location.

Parameters

• width: -1 if unknown ideally the width/height should be known in advance

• height: -1 if unknown ideally the width/height should be known in advance

Method Details

createMulti

public static EncodedImage createMulti(int[] dpis,
 byte[][] data)

Creates an encoded image that acts as a multi-image, DO NOT USE THIS METHOD. Its for internal use to improve the user experience of the simulator

Parameters

• dpis: device DPI's

• data: the data matching each multi-image DPI

Returns

an encoded image that acts as a multi-image in runtime

Deprecated

createFromImage

public static EncodedImage createFromImage(Image i,
 boolean jpeg)

Converts an image to encoded image

Parameters

• i: image

• jpeg: true to try and set jpeg, will do a best effort but this isn't guaranteed

Returns

an encoded image or null

createFromRGB

public static Image createFromRGB(int[] argb,
 int width,
 int height,
 boolean jpeg)

Tries to create an encoded image from RGB which is more efficient, however if this fails it falls back to regular RGB image. This method is slower than creating an RGB image (not to be confused with the RGBImage class which is something ENTIRELY different!).

Parameters

• argb: an argb array

• width: the width for the image

• height: the height for the image

• jpeg: uses jpeg format internally which is opaque and could be faster/smaller

Returns

an image which we hope is an encoded image

create

public static EncodedImage create(byte[] data)

Creates an image from the given byte array

Parameters

• data: the data of the image

Returns

newly created encoded image

create

public static EncodedImage create(byte[] data,
 int width,
 int height,
 boolean opacity)

Creates an image from the given byte array with the variables set appropriately. This saves LWUIT allot of resources since it doesn't need to actually traverse the pixels of an image to find out details about it.

Parameters

• data: the data of the image

• width: the width of the image

• height: the height of the image

• opacity: true for an opaque image

Returns

newly created encoded image

create

public static EncodedImage create(InputStream i)
                           throws IOException

Creates an image from the input stream

Parameters

• i: the input stream

Returns

newly created encoded image

Throws

• java.io.IOException: if thrown by the input stream

Throws:

IOException

create

public static EncodedImage create(InputStream i,
 int size)
                           throws IOException

Creates an image from the input stream, this version of the method is somewhat faster than the version that doesn't accept size

Parameters

• i: the input stream

• size: the size of the stream

Returns

newly created encoded image

Throws

• java.io.IOException: if thrown by the input stream

Throws:

IOException

create

public static EncodedImage create(String i)
                           throws IOException

Creates an image from the input stream

Parameters

• i: the resource

Returns

newly created encoded image

Throws

• java.io.IOException: if thrown by the input stream

Throws:

IOException

resetCache

protected void resetCache()

A subclass might choose to load asynchroniously and reset the cache when the image is ready.

getImageData

public byte[] getImageData()

Returns the byte array data backing the image allowing the image to be stored and discarded completely from RAM.

Returns

byte array used to create the image, e.g. encoded PNG, JPEG etc.

getImage

public Object getImage()

Returns the platform specific image implementation, warning the implementation class can change between revisions of Codename One and platforms.

Returns

platform specific native implementation for this image object

Overrides:

getImage in class Image

getInternal

protected Image getInternal()

Returns the actual image represented by the encoded image, this image will be cached in a weak/soft reference internally. This method is useful to detect when the system actually created an image instance. You shouldn't invoke this method manually!

Returns

drawable image instance

isLocked

public boolean isLocked()

Returns true if the image is locked

Returns

false by default

Overrides:

isLocked in class Image

asyncLock

public void asyncLock(Image internal)

Async lock is the equivalent of a lock operation, however it uses the given image as the hard cache and performs the actual image loading asynchronously. On completion this method will invoke repaint on the main form if applicable.

Parameters

• internal: the image to show while the actual image loads.

Overrides:

asyncLock in class Image

lock

public void lock()

This callback indicates that a component pointing at this image is initialized, this allows an image to make performance sensitive considerations e.g. an encoded image might choose to cache itself in RAM. This method may be invoked multiple times.

Overrides:

lock in class Image

unlock

public void unlock()

This callback indicates that a component pointing at this image is now deinitilized This method may be invoked multiple times.

Overrides:

unlock in class Image

subImage

public Image subImage(int x,
 int y,
 int width,
 int height,
 boolean processAlpha)

Extracts a subimage from the given image allowing us to breakdown a single large image into multiple smaller images in RAM, this actually creates a standalone version of the image for use.

Parameters

• x: the x offset from the image

• y: the y offset from the image

• width: the width of internal images

• height: the height of internal images

• processAlpha: whether alpha should be processed as well as part of the cutting

Returns

An array of all the possible images that can be created from the source

Overrides:

subImage in class Image

rotate

public Image rotate(int degrees)

Returns an instance of this image rotated by the given number of degrees. By default 90 degree angle divisions are supported, anything else is implementation dependent. This method assumes a square image. Notice that it is inefficient in the current implementation to rotate to non-square angles,

E.g. rotating an image to 45, 90 and 135 degrees is inefficient. Use rotatate to 45, 90 and then rotate the 45 to another 90 degrees to achieve the same effect with less memory.

Parameters

• degrees: A degree in right angle must be larger than 0 and up to 359 degrees

Returns

new image instance with the closest possible rotation

Overrides:

rotate in class Image

modifyAlpha

public Image modifyAlpha(byte alpha)

Creates a new image instance with the alpha channel of opaque/translucent pixels within the image using the new alpha value. Transparent (alpha == 0) pixels remain transparent. All other pixels will have the new alpha value.

Parameters

• alpha: New value for the entire alpha channel

Returns

Overrides:

modifyAlpha in class Image

Returns:

Translucent/Opaque image based on the alpha value and the pixels of this image

modifyAlpha

public Image modifyAlpha(byte alpha,
 int removeColor)

Creates a new image instance with the alpha channel of opaque/translucent pixels within the image using the new alpha value. Transparent (alpha == 0) pixels remain transparent. All other pixels will have the new alpha value.

Parameters

• alpha: New value for the entire alpha channel

• removeColor: pixels matching this color are made transparent (alpha channel ignored)

Returns

Overrides:

modifyAlpha in class Image

Returns:

Translucent/Opaque image based on the alpha value and the pixels of this image

getGraphics

public Graphics getGraphics()

If this is a mutable image a graphics object allowing us to draw on it is returned.

Returns

Graphics object allowing us to manipulate the content of a mutable image

Overrides:

getGraphics in class Image

getWidth

public int getWidth()

Returns the width of the image

Returns

the width of the image

Overrides:

getWidth in class Image

getHeight

public int getHeight()

Returns the height of the image

Returns

the height of the image

Overrides:

getHeight in class Image

drawImage

protected void drawImage(Graphics g,
 Object nativeGraphics,
 int x,
 int y)

Callback invoked internally by Codename One to draw the image/frame onto the display. Image subclasses can override this method to perform drawing of custom image types.

Parameters

• g: the graphics object

• nativeGraphics: the underlying native graphics which might be essential for some image types

• x: the x coordinate

• y: the y coordinate

Overrides:

drawImage in class Image

drawImage

protected void drawImage(Graphics g,
 Object nativeGraphics,
 int x,
 int y,
 int w,
 int h)

Callback invoked internally by Codename One to draw the image/frame onto the display. Image subclasses can override this method to perform drawing of custom image types.

Parameters

• g: the graphics object

• nativeGraphics: the underlying native graphics which might be essential for some image types

• x: the x coordinate

• y: the y coordinate

• w: the width to occupy

• h: the height to occupy

Overrides:

drawImage in class Image

toRGB

public void toRGB(RGBImage image,
 int destX,
 int destY,
 int x,
 int y,
 int width,
 int height)

Extracts data from this image into the given RGBImage

Parameters

• image: RGBImage that would receive pixel data

• destX: @param destX x location within RGBImage into which the data will be written

• destY: @param destY y location within RGBImage into which the data will be written

• x: location within the source image

• y: location within the source image

• width: size of the image to extract from the source image

• height: size of the image to extract from the source image

Overrides:

toRGB in class Image

scaledWidth

public Image scaledWidth(int width)

Scales the image to the given width while updating the height based on the aspect ratio of the width

Parameters

• width: the given new image width

Returns

the newly created image

Overrides:

scaledWidth in class Image

scaledHeight

public Image scaledHeight(int height)

Scales the image to the given height while updating the width based on the aspect ratio of the height

Parameters

• height: the given new image height

Returns

the newly created image

Overrides:

scaledHeight in class Image

scaledSmallerRatio

public Image scaledSmallerRatio(int width,
 int height)

Scales the image while maintaining the aspect ratio to the smaller size image

Parameters

• width: the given new image width

• height: the given new image height

Returns

the newly created image

Overrides:

scaledSmallerRatio in class Image

scaledEncoded

public EncodedImage scaledEncoded(int width,
 int height)

Performs scaling using ImageIO to generate an encoded Image

Parameters

• width: the width of the image, -1 to scale based on height and preserve aspect ratio

• height: the height of the image, -1 to scale based on width and preserve aspect ratio

Returns

new encoded image

scaled

public Image scaled(int width,
 int height)

Returns a scaled version of this image image using the given width and height, this is a fast algorithm that preserves translucent information. The method accepts -1 to preserve aspect ratio in the given axis.

Parameters

• width: width for the scaling

• height: height of the scaled image

Returns

new image instance scaled to the given height and width

Overrides:

scaled in class Image

scale

public void scale(int width,
 int height)

Scale the image to the given width and height, this is a fast algorithm that preserves translucent information

Parameters

• width: width for the scaling

• height: height of the scaled image

Deprecated

Overrides:

scale in class Image

isAnimation

public boolean isAnimation()

Returns true if this is an animated image

Returns

true if this image represents an animation

Overrides:

isAnimation in class Image

isOpaque

public boolean isOpaque()

Indicates whether this image is opaque or not

Returns

true if the image is completely opqaque which allows for some heavy optimizations

Overrides:

isOpaque in class Image