com.davemorrissey.labs.subscaleview.decoder

Class SkiaImageRegionDecoder

java.lang.Object

com.davemorrissey.labs.subscaleview.decoder.SkiaImageRegionDecoder

All Implemented Interfaces:

ImageRegionDecoder

public class SkiaImageRegionDecoder
extends Object
implements ImageRegionDecoder

Default implementation of ImageRegionDecoder using Android's BitmapRegionDecoder, based on the Skia library. This works well in most circumstances and has reasonable performance due to the cached decoder instance, however it has some problems with grayscale, indexed and CMYK images. A ReadWriteLock is used to delegate responsibility for multi threading behaviour to the BitmapRegionDecoder instance on SDK >= 21, whilst allowing this class to block until no tiles are being loaded before recycling the decoder. In practice, BitmapRegionDecoder is synchronized internally so this has no real impact on performance.

Constructor Summary

Constructors

Constructor and Description
SkiaImageRegionDecoder()
SkiaImageRegionDecoder(Bitmap.Config bitmapConfig)

Method Summary

Modifier and Type	Method and Description
Bitmap	decodeRegion(Rect sRect, int sampleSize) Decode a region of the image with the given sample size.
Point	init(Context context, Uri uri) Initialise the decoder.
boolean	isReady() Status check.
void	recycle() This method will be called when the decoder is no longer required.

Methods inherited from class java.lang.Object

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

Constructor Detail

SkiaImageRegionDecoder

public SkiaImageRegionDecoder()

SkiaImageRegionDecoder

public SkiaImageRegionDecoder(Bitmap.Config bitmapConfig)

Method Detail

init

public Point init(Context context,
                  Uri uri)
           throws Exception

Description copied from interface: ImageRegionDecoder

Initialise the decoder. When possible, perform initial setup work once in this method. The dimensions of the image must be returned. The URI can be in one of the following formats:
File: file:///scard/picture.jpg
Asset: file:///android_asset/picture.png
Resource: android.resource://com.example.app/drawable/picture

Specified by:

init in interface ImageRegionDecoder

Parameters:

context - Application context. A reference may be held, but must be cleared on recycle.

uri - URI of the image.

Returns:

Dimensions of the image.

Throws:

Exception - if initialisation fails.

decodeRegion

public Bitmap decodeRegion(Rect sRect,
                           int sampleSize)

Description copied from interface: ImageRegionDecoder

Decode a region of the image with the given sample size. This method is called off the UI thread so it can safely load the image on the current thread. It is called from AsyncTasks running in an executor that may have multiple threads, so implementations must be thread safe. Adding synchronized to the method signature is the simplest way to achieve this, but bear in mind the ImageRegionDecoder.recycle() method can be called concurrently.

See SkiaImageRegionDecoder and SkiaPooledImageRegionDecoder for examples of internal locking and synchronization.

Specified by:

decodeRegion in interface ImageRegionDecoder

Parameters:

sRect - Source image rectangle to decode.

sampleSize - Sample size.

Returns:

The decoded region. It is safe to return null if decoding fails.

isReady

public boolean isReady()

Description copied from interface: ImageRegionDecoder

Status check. Should return false before initialisation and after recycle.

Specified by:

isReady in interface ImageRegionDecoder

Returns:

true if the decoder is ready to be used.

recycle

public void recycle()

Description copied from interface: ImageRegionDecoder

This method will be called when the decoder is no longer required. It should clean up any resources still in use.

Specified by:

recycle in interface ImageRegionDecoder