com.davemorrissey.labs.subscaleview.decoder

Interface ImageRegionDecoder

All Known Implementing Classes:

SkiaImageRegionDecoder, SkiaPooledImageRegionDecoder

public interface ImageRegionDecoder

Interface for image decoding classes, allowing the default BitmapRegionDecoder based on the Skia library to be replaced with a custom class.

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.

Method Detail

init

Point init(Context context,
           Uri uri)
    throws Exception

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

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

Bitmap decodeRegion(Rect sRect,
                    int sampleSize)

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 recycle() method can be called concurrently.

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

Parameters:

sRect - Source image rectangle to decode.

sampleSize - Sample size.

Returns:

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

isReady

boolean isReady()

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

Returns:

true if the decoder is ready to be used.

recycle

void recycle()

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