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# ImageDecoder

`public final class ImageDecoder`
`extends Object` `implements AutoCloseable`

java.lang.Object
↳ | android.graphics.ImageDecoder

A class for converting encoded images (like `PNG`, `JPEG`, `WEBP`, `GIF`, or `HEIF`) into `Drawable` or `Bitmap` objects.

To use it, first create a `Source` using one of the `createSource` overloads. For example, to decode from a `Uri`, call `createSource(android.content.ContentResolver, android.net.Uri)` and pass the result to `decodeDrawable(android.graphics.ImageDecoder.Source)` or `decodeBitmap(android.graphics.ImageDecoder.Source)`:

      File file = new File(...);
      ImageDecoder.Source source = ImageDecoder.createSource(file);
      Drawable drawable = ImageDecoder.decodeDrawable(source);

To change the default settings, pass the `Source` and an `OnHeaderDecodedListener` to `decodeDrawable(android.graphics.ImageDecoder.Source, android.graphics.ImageDecoder.OnHeaderDecodedListener)` or `decodeBitmap(android.graphics.ImageDecoder.Source, android.graphics.ImageDecoder.OnHeaderDecodedListener)`. For example, to create a sampled image with half the width and height of the original image, call `setTargetSampleSize(2)` inside `onHeaderDecoded`:

      OnHeaderDecodedListener listener = new OnHeaderDecodedListener() {
          public void onHeaderDecoded(ImageDecoder decoder, ImageInfo info, Source source) {
              decoder.setTargetSampleSize(2);
          }
      };
      Drawable drawable = ImageDecoder.decodeDrawable(source, listener);

The `ImageInfo` contains information about the encoded image, like its width and height, and the `Source` can be used to match to a particular `Source` if a single `OnHeaderDecodedListener` is used with multiple `Source` objects.

The `OnHeaderDecodedListener` can also be implemented as a lambda:

      Drawable drawable = ImageDecoder.decodeDrawable(source, (decoder, info, src) -> {
          decoder.setTargetSampleSize(2);
      });

If the encoded image is an animated `GIF` or `WEBP`, `decodeDrawable` will return an `AnimatedImageDrawable`. To start its animation, call `AnimatedImageDrawable.start()`:

      Drawable drawable = ImageDecoder.decodeDrawable(source);
      if (drawable instanceof AnimatedImageDrawable) {
          ((AnimatedImageDrawable) drawable).start();
      }

By default, a `Bitmap` created by `ImageDecoder` (including one that is inside a `Drawable`) will be immutable (i.e. `Bitmap.isMutable()` returns `false`), and it will typically have `Config` `Bitmap.Config#HARDWARE`. Although these properties can be changed with `setMutableRequired(true)` (which is only compatible with `decodeBitmap(android.graphics.ImageDecoder.Source)` and `decodeBitmap(android.graphics.ImageDecoder.Source, android.graphics.ImageDecoder.OnHeaderDecodedListener)`) and `setAllocator(int)`, it is also possible to apply custom effects regardless of the mutability of the final returned object by passing a `PostProcessor` to `setPostProcessor`. A `PostProcessor` can also be a lambda:

      Drawable drawable = ImageDecoder.decodeDrawable(source, (decoder, info, src) -> {
          decoder.setPostProcessor((canvas) -> {
                  // This will create rounded corners.
                  Path path = new Path();
                  path.setFillType(Path.FillType.INVERSE_EVEN_ODD);
                  int width = canvas.getWidth();
                  int height = canvas.getHeight();
                  path.addRoundRect(0, 0, width, height, 20, 20, Path.Direction.CW);
                  Paint paint = new Paint();
                  paint.setAntiAlias(true);
                  paint.setColor(Color.TRANSPARENT);
                  paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
                  canvas.drawPath(path, paint);
                  return PixelFormat.TRANSLUCENT;
          });
      });

If the encoded image is incomplete or contains an error, or if an `Exception` occurs during decoding, a `DecodeException` will be thrown. In some cases, the `ImageDecoder` may have decoded part of the image. In order to display the partial image, an `OnPartialImageListener` must be passed to `setOnPartialImageListener`. For example:

      Drawable drawable = ImageDecoder.decodeDrawable(source, (decoder, info, src) -> {
          decoder.setOnPartialImageListener((DecodeException e) -> {
                  // Returning true indicates to create a Drawable or Bitmap even
                  // if the whole image could not be decoded. Any remaining lines
                  // will be blank.
                  return true;
          });
      });

## Summary

### Nested classes
`class` | `ImageDecoder.DecodeException` Information about an interrupted decode.
`class` | `ImageDecoder.ImageInfo` Information about an encoded image.
`interface` | `ImageDecoder.OnHeaderDecodedListener` Interface for changing the default settings of a decode.
`interface` | `ImageDecoder.OnPartialImageListener` Interface for inspecting a `DecodeException` and potentially preventing it from being thrown.
`class` | `ImageDecoder.Source` Source of encoded image data.

### Constants
`int` | `ALLOCATOR_DEFAULT` Use the default allocation for the pixel memory.
`int` | `ALLOCATOR_HARDWARE` Require a `Bitmap.Config#HARDWARE` `Bitmap`.
`int` | `ALLOCATOR_SHARED_MEMORY` Use shared memory for the pixel memory.
`int` | `ALLOCATOR_SOFTWARE` Use a software allocation for the pixel memory.
`int` | `MEMORY_POLICY_DEFAULT` Use the most natural `Bitmap.Config` for the internal `Bitmap`.
`int` | `MEMORY_POLICY_LOW_RAM` Save memory if possible by using a denser `Bitmap.Config` at the cost of some image quality.

### Public methods
`void` | `close()` Closes this resource, relinquishing any underlying resources.
`static ImageDecoder.Source` | `createSource(byte[] data)` Create a new `Source` from a byte array.
`static ImageDecoder.Source` | `createSource(AssetManager assets, String fileName)` Create a new `Source` from a file in the "assets" directory.
`static ImageDecoder.Source` | `createSource(Callable<AssetFileDescriptor> callable)` Create a new `Source` from a `Callable` that returns a new `AssetFileDescriptor` for each request.
`static ImageDecoder.Source` | `createSource(ByteBuffer buffer)` Create a new `Source` from a `ByteBuffer`.
`static ImageDecoder.Source` | `createSource(File file)` Create a new `Source` from a `File`.
`static ImageDecoder.Source` | `createSource(Resources res, int resId)` Create a new `Source` from a resource.
`static ImageDecoder.Source` | `createSource(ContentResolver cr, Uri uri)` Create a new `Source` from a `Uri`.
`static ImageDecoder.Source` | `createSource(byte[] data, int offset, int length)` Create a new `Source` from a byte array.
`static Bitmap` | `decodeBitmap(ImageDecoder.Source src, ImageDecoder.OnHeaderDecodedListener listener)` Create a `Bitmap` from a `Source`.
`static Bitmap` | `decodeBitmap(ImageDecoder.Source src)` Create a `Bitmap` from a `Source`.
`static Drawable` | `decodeDrawable(ImageDecoder.Source src)` Create a `Drawable` from a `Source`.
`static Drawable` | `decodeDrawable(ImageDecoder.Source src, ImageDecoder.OnHeaderDecodedListener listener)` Create a `Drawable` from a `Source`.
`int` | `getAllocator()` Return the allocator for the pixel memory.
`Rect` | `getCrop()` Return the cropping rectangle, if set.
`int` | `getMemorySizePolicy()` Retrieve the memory policy for the decoded `Bitmap`.
`ImageDecoder.OnPartialImageListener` | `getOnPartialImageListener()` Return the `OnPartialImageListener` currently set.
`PostProcessor` | `getPostProcessor()` Return the `PostProcessor` currently set.
`boolean` | `isDecodeAsAlphaMaskEnabled()` Return whether to treat single channel input as alpha.
`static boolean` | `isMimeTypeSupported(String mimeType)` Return if the given MIME type is a supported file format that can be decoded by this class.
`boolean` | `isMutableRequired()` Return whether the decoded `Bitmap` will be mutable.
`boolean` | `isUnpremultipliedRequired()` Return whether the `Bitmap` will have unpremultiplied pixels.
`void` | `setAllocator(int allocator)` Choose the backing for the pixel memory.
`void` | `setCrop(Rect subset)` Crop the output to `subset` of the (possibly) scaled image.
`void` | `setDecodeAsAlphaMaskEnabled(boolean enabled)` Specify whether to potentially treat the output as an alpha mask.
`void` | `setMemorySizePolicy(int policy)` Specify the memory policy for the decoded `Bitmap`.
`void` | `setMutableRequired(boolean mutable)` Specify whether the `Bitmap` should be mutable.
`void` | `setOnPartialImageListener(ImageDecoder.OnPartialImageListener listener)` Set (replace) the `OnPartialImageListener` on this object.
`void` | `setPostProcessor(PostProcessor postProcessor)` Modify the image after decoding and scaling.
`void` | `setTargetColorSpace(ColorSpace colorSpace)` Specify the desired `ColorSpace` for the output.
`void` | `setTargetSampleSize(int sampleSize)` Set the target size with a sampleSize.
`void` | `setTargetSize(int width, int height)` Specify the size of the output `Drawable` or `Bitmap`.
`void` | `setUnpremultipliedRequired(boolean unpremultipliedRequired)` Specify whether the `Bitmap` should have unpremultiplied pixels.

### Protected methods
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

### Inherited methods
From class `java.lang.Object`
`Object` | `clone()` Creates and returns a copy of this object.
`boolean` | `equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>` | `getClass()` Returns the runtime class of this `Object`.
`int` | `hashCode()` Returns a hash code value for the 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(long timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void` | `wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void` | `wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
From interface `java.lang.AutoCloseable`
`abstract void` | `close()` Closes this resource, relinquishing any underlying resources.

## Constants

### ALLOCATOR_DEFAULT

    public static final int ALLOCATOR_DEFAULT

Use the default allocation for the pixel memory. Will typically result in a `Bitmap.Config#HARDWARE` allocation, but may be software for small images. In addition, this will switch to software when HARDWARE is incompatible, e.g. `setMutableRequired(true)` or `setDecodeAsAlphaMaskEnabled(true)`.

Constant Value: 0 (0x00000000)

### ALLOCATOR_HARDWARE

    public static final int ALLOCATOR_HARDWARE

Require a `Bitmap.Config#HARDWARE` `Bitmap`.

When this is combined with incompatible options, like `setMutableRequired(true)` or `setDecodeAsAlphaMaskEnabled(true)`, `decodeDrawable` or `decodeBitmap` will throw an `IllegalStateException`.

Constant Value: 3 (0x00000003)

### ALLOCATOR_SHARED_MEMORY

    public static final int ALLOCATOR_SHARED_MEMORY

Use shared memory for the pixel memory.

Useful for sharing across processes.

Constant Value: 2 (0x00000002)

### ALLOCATOR_SOFTWARE

    public static final int ALLOCATOR_SOFTWARE

Use a software allocation for the pixel memory.

Useful for drawing to a software `Canvas` or for accessing the pixels on the final output.

Constant Value: 1 (0x00000001)

### MEMORY_POLICY_DEFAULT

    public static final int MEMORY_POLICY_DEFAULT

Use the most natural `Bitmap.Config` for the internal `Bitmap`.

This is the recommended default for most applications and usages. This will use the closest `Bitmap.Config` for the encoded source. If the encoded source does not exactly match any `Bitmap.Config`, the next highest quality `Bitmap.Config` will be used avoiding any loss in image quality.

Constant Value: 1 (0x00000001)

### MEMORY_POLICY_LOW_RAM

    public static final int MEMORY_POLICY_LOW_RAM

Save memory if possible by using a denser `Bitmap.Config` at the cost of some image quality.

For example an opaque 8-bit image may be compressed into an `Bitmap.Config#RGB_565` configuration, sacrificing image quality to save memory.

Constant Value: 0 (0x00000000)

## Public methods

### close

    public void close ()

Closes this resource, relinquishing any underlying resources. This method is invoked automatically on objects managed by the try-with-resources statement.

This is an implementation detail of `ImageDecoder`, and should never be called manually.

### createSource

    public static ImageDecoder.Source createSource (byte[] data)

Create a new `Source` from a byte array.

Note: If this `Source` is passed to `decodeDrawable`, and the encoded image is animated, the returned `AnimatedImageDrawable` will continue reading from `data`, so its contents must not be modified, even after the `AnimatedImageDrawable` is returned. `data`'s contents should never be modified during decode.

This method is safe to call from any thread.

Parameters
`data` | `byte`: byte array of compressed image data. This value cannot be `null`.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`.

Throws
`NullPointerException` | if data is null.

### createSource

    public static ImageDecoder.Source createSource (AssetManager assets,
                    String fileName)

Create a new `Source` from a file in the "assets" directory.
This method is safe to call from any thread.

Parameters
`assets` | `AssetManager`: This value cannot be `null`.
`fileName` | `String`: This value cannot be `null`.

Returns
`ImageDecoder.Source` | This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (Callable<AssetFileDescriptor> callable)

Create a new `Source` from a `Callable` that returns a new `AssetFileDescriptor` for each request. This provides control over how the `AssetFileDescriptor` is created, such as passing options into `ContentResolver#openTypedAssetFileDescriptor`, or enabling use of a `CancellationSignal`.

It's important for the given `Callable` to return a new, unique `AssetFileDescriptor` for each invocation, to support reuse of the returned `Source`.
This method is safe to call from any thread.

Parameters
`callable` | `Callable`: This value cannot be `null`.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`. This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (ByteBuffer buffer)

Create a new `Source` from a `ByteBuffer`.

Decoding will start from `buffer.position()`. The position of `buffer` will not be affected.

Note: If this `Source` is passed to `decodeDrawable`, and the encoded image is animated, the returned `AnimatedImageDrawable` will continue reading from the `buffer`, so its contents must not be modified, even after the `AnimatedImageDrawable` is returned. `buffer`'s contents should never be modified during decode.

This method is safe to call from any thread.

Parameters
`buffer` | `ByteBuffer`: This value cannot be `null`.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`. This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (File file)

Create a new `Source` from a `File`.

This method should only be used for files that you have direct access to; if you'd like to work with files hosted outside your app, use an API like `createSource(java.util.concurrent.Callable)` or `createSource(android.content.ContentResolver, android.net.Uri)`.
This method is safe to call from any thread.

Parameters
`file` | `File`: This value cannot be `null`.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`. This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (Resources res,
                    int resId)

Create a new `Source` from a resource.
This method is safe to call from any thread.

Parameters
`res` | `Resources`: the `Resources` object containing the image data. This value cannot be `null`.
`resId` | `int`: resource ID of the image data.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`. This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (ContentResolver cr,
                    Uri uri)

Create a new `Source` from a `Uri`.

##### Accepts the following URI schemes:

- content (`ContentResolver#SCHEME_CONTENT`)
- android.resource (`ContentResolver#SCHEME_ANDROID_RESOURCE`)
- file (`ContentResolver#SCHEME_FILE`)

This method is safe to call from any thread.

Parameters
`cr` | `ContentResolver`: to retrieve from. This value cannot be `null`.
`uri` | `Uri`: of the image file. This value cannot be `null`.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`. This value cannot be `null`.

### createSource

    public static ImageDecoder.Source createSource (byte[] data,
                    int offset,
                    int length)

Create a new `Source` from a byte array.

Note: If this `Source` is passed to `decodeDrawable`, and the encoded image is animated, the returned `AnimatedImageDrawable` will continue reading from `data`, so its contents must not be modified, even after the `AnimatedImageDrawable` is returned. `data`'s contents should never be modified during decode.

This method is safe to call from any thread.

Parameters
`data` | `byte`: byte array of compressed image data. This value cannot be `null`.
`offset` | `int`: offset into data for where the decoder should begin parsing.
`length` | `int`: number of bytes, beginning at offset, to parse.

Returns
`ImageDecoder.Source` | a new Source object, which can be passed to `decodeDrawable` or `decodeBitmap`.

Throws
`NullPointerException` | if data is null.
`ArrayIndexOutOfBoundsException` | if offset and length are not within data.

### decodeBitmap

    public static Bitmap decodeBitmap (ImageDecoder.Source src,
                    ImageDecoder.OnHeaderDecodedListener listener)

Create a `Bitmap` from a `Source`.
This method may take several seconds to complete, so it should only be called from a worker thread.

Parameters
`src` | `ImageDecoder.Source`: representing the encoded image. This value cannot be `null`.
`listener` | `ImageDecoder.OnHeaderDecodedListener`: for learning the `ImageInfo` and changing any default settings on the `ImageDecoder`. This will be called on the same thread as `decodeBitmap` before that method returns. This is required in order to change any of the default settings. This value cannot be `null`.

Returns
`Bitmap` | Bitmap containing the image. This value cannot be `null`.

Throws
`IOException` | if `src` is not found, is an unsupported format, or cannot be decoded for any reason.

### decodeBitmap

    public static Bitmap decodeBitmap (ImageDecoder.Source src)

Create a `Bitmap` from a `Source`.

Since there is no `OnHeaderDecodedListener`, the default settings will be used. In order to change any settings, call `decodeBitmap(android.graphics.ImageDecoder.Source, android.graphics.ImageDecoder.OnHeaderDecodedListener)` instead.

This method may take several seconds to complete, so it should only be called from a worker thread.

Parameters
`src` | `ImageDecoder.Source`: representing the encoded image. This value cannot be `null`.

Returns
`Bitmap` | Bitmap containing the image. This value cannot be `null`.

Throws
`IOException` | if `src` is not found, is an unsupported format, or cannot be decoded for any reason.

### decodeDrawable

    public static Drawable decodeDrawable (ImageDecoder.Source src)

Create a `Drawable` from a `Source`.

Since there is no `OnHeaderDecodedListener`, the default settings will be used. In order to change any settings, call `decodeDrawable(android.graphics.ImageDecoder.Source, android.graphics.ImageDecoder.OnHeaderDecodedListener)` instead.

This method may take several seconds to complete, so it should only be called from a worker thread.

Parameters
`src` | `ImageDecoder.Source`: representing the encoded image. This value cannot be `null`.

Returns
`Drawable` | Drawable for displaying the image. This value cannot be `null`.

Throws
`IOException` | if `src` is not found, is an unsupported format, or cannot be decoded for any reason.

### decodeDrawable

    public static Drawable decodeDrawable (ImageDecoder.Source src,
                    ImageDecoder.OnHeaderDecodedListener listener)

Create a `Drawable` from a `Source`.
This method may take several seconds to complete, so it should only be called from a worker thread.

Parameters
`src` | `ImageDecoder.Source`: representing the encoded image. This value cannot be `null`.
`listener` | `ImageDecoder.OnHeaderDecodedListener`: for learning the `ImageInfo` and changing any default settings on the `ImageDecoder`. This will be called on the same thread as `decodeDrawable` before that method returns. This is required in order to change any of the default settings. This value cannot be `null`.

Returns
`Drawable` | Drawable for displaying the image. This value cannot be `null`.

Throws
`IOException` | if `src` is not found, is an unsupported format, or cannot be decoded for any reason.

### getAllocator

    public int getAllocator ()

Return the allocator for the pixel memory.

Returns
`int` | Value is `ALLOCATOR_DEFAULT`, `ALLOCATOR_SOFTWARE`, `ALLOCATOR_SHARED_MEMORY`, or `ALLOCATOR_HARDWARE`

### getCrop

    public Rect getCrop ()

Return the cropping rectangle, if set.

Returns
`Rect` | This value may be `null`.

### getMemorySizePolicy

    public int getMemorySizePolicy ()

Retrieve the memory policy for the decoded `Bitmap`.

Returns
`int` | Value is `MEMORY_POLICY_DEFAULT`, or `MEMORY_POLICY_LOW_RAM`

### getOnPartialImageListener

    public ImageDecoder.OnPartialImageListener getOnPartialImageListener ()

Return the `OnPartialImageListener` currently set.

Returns
`ImageDecoder.OnPartialImageListener` | This value may be `null`.

### getPostProcessor

    public PostProcessor getPostProcessor ()

Return the `PostProcessor` currently set.

Returns
`PostProcessor` | This value may be `null`.

### isDecodeAsAlphaMaskEnabled

    public boolean isDecodeAsAlphaMaskEnabled ()

Return whether to treat single channel input as alpha.

This returns whether `setDecodeAsAlphaMaskEnabled(boolean)` was set to `true`. It may still return `true` even if the image has more than one channel and therefore will not be treated as an alpha mask.

Returns
`boolean` |

### isMimeTypeSupported

    public static boolean isMimeTypeSupported (String mimeType)

Return if the given MIME type is a supported file format that can be decoded by this class. This can be useful to determine if a file can be decoded directly, or if it needs to be converted into a more general format using an API like `ContentResolver#openTypedAssetFile`.

Parameters
`mimeType` | `String`: This value cannot be `null`.

Returns
`boolean` |

### isMutableRequired

    public boolean isMutableRequired ()

Return whether the decoded `Bitmap` will be mutable.

Returns
`boolean` |

### isUnpremultipliedRequired

    public boolean isUnpremultipliedRequired ()

Return whether the `Bitmap` will have unpremultiplied pixels.

Returns
`boolean` |

### setAllocator

    public void setAllocator (int allocator)

Choose the backing for the pixel memory.

This is ignored for animated drawables.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`allocator` | `int`: Type of allocator to use. Value is `ALLOCATOR_DEFAULT`, `ALLOCATOR_SOFTWARE`, `ALLOCATOR_SHARED_MEMORY`, or `ALLOCATOR_HARDWARE`

### setCrop

    public void setCrop (Rect subset)

Crop the output to `subset` of the (possibly) scaled image.

`subset` must be contained within the size set by `setTargetSize(int, int)` or the bounds of the image if setTargetSize was not called. Otherwise an `IllegalStateException` will be thrown by `decodeDrawable`/`decodeBitmap`.

NOT intended as a replacement for `BitmapRegionDecoder.decodeRegion()`. This supports all formats, but merely crops the output.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`subset` | `Rect`: This value may be `null`.

### setDecodeAsAlphaMaskEnabled

    public void setDecodeAsAlphaMaskEnabled (boolean enabled)

Specify whether to potentially treat the output as an alpha mask.

If this is set to `true` and the image is encoded in a format with only one channel, treat that channel as alpha. Otherwise this call has no effect.

This is incompatible with `ALLOCATOR_HARDWARE`. Trying to combine them will result in `decodeDrawable`/ `decodeBitmap` throwing an `IllegalStateException`.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`enabled` | `boolean`

### setMemorySizePolicy

    public void setMemorySizePolicy (int policy)

Specify the memory policy for the decoded `Bitmap`.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`policy` | `int`: Value is `MEMORY_POLICY_DEFAULT`, or `MEMORY_POLICY_LOW_RAM`

### setMutableRequired

    public void setMutableRequired (boolean mutable)

Specify whether the `Bitmap` should be mutable.

By default, a `Bitmap` created by `decodeBitmap` will be immutable i.e. `Bitmap.isMutable()` returns `false`. This can be changed with `setMutableRequired(true)`.

Mutable Bitmaps are incompatible with `ALLOCATOR_HARDWARE`, because `Bitmap.Config#HARDWARE` Bitmaps cannot be mutable. Attempting to combine them will throw an `IllegalStateException`.

Mutable Bitmaps are also incompatible with `decodeDrawable`, which would require retrieving the Bitmap from the returned Drawable in order to modify. Attempting to decode a mutable `Drawable` will throw an `IllegalStateException`.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`mutable` | `boolean`

### setOnPartialImageListener

    public void setOnPartialImageListener (ImageDecoder.OnPartialImageListener listener)

Set (replace) the `OnPartialImageListener` on this object.

Will be called if there is an error in the input. Without one, an error will result in an `Exception` being thrown.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`listener` | `ImageDecoder.OnPartialImageListener`: This value may be `null`.

### setPostProcessor

    public void setPostProcessor (PostProcessor postProcessor)

Modify the image after decoding and scaling.

This allows adding effects prior to returning a `Drawable` or `Bitmap`. For a `Drawable` or an immutable `Bitmap`, this is the only way to process the image after decoding.

If combined with `setTargetSize(int, int)` and/or `setCrop(Rect)`, `PostProcessor#onPostProcess` occurs last.

If set on a nine-patch image, the nine-patch data is ignored.

For an animated image, the drawing commands drawn on the `Canvas` will be recorded immediately and then applied to each frame.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`postProcessor` | `PostProcessor`: This value may be `null`.

### setTargetColorSpace

    public void setTargetColorSpace (ColorSpace colorSpace)

Specify the desired `ColorSpace` for the output.

If non-null, the decoder will try to decode into `colorSpace`. If it is null, which is the default, or the request cannot be met, the decoder will pick either the color space embedded in the image or the `ColorSpace` best suited for the requested image configuration (for instance `sRGB` for the `Bitmap.Config#ARGB_8888` configuration and `EXTENDED_SRGB` for `Bitmap.Config#RGBA_F16`).

Only `ColorSpace.Model#RGB` color spaces are currently supported. An `IllegalArgumentException` will be thrown by `decodeDrawable`/ `decodeBitmap` when setting a non-RGB color space such as `Lab`.

The specified color space's transfer function must be an `ICC parametric curve`. An `IllegalArgumentException` will be thrown by the decode methods if calling `ColorSpace.Rgb#getTransferParameters()` on the specified color space returns null.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`colorSpace` | `ColorSpace`

### setTargetSampleSize

    public void setTargetSampleSize (int sampleSize)

Set the target size with a sampleSize.

By default, the output size will match the size of the encoded image, which can be retrieved from the `ImageInfo` in `onHeaderDecoded`.

Requests the decoder to subsample the original image, returning a smaller image to save memory. The `sampleSize` is the number of pixels in either dimension that correspond to a single pixel in the output. For example, `sampleSize == 4` returns an image that is 1/4 the width/height of the original, and 1/16 the number of pixels.

Must be greater than or equal to 1.

This has the same effect as calling `setTargetSize(int, int)` with dimensions based on the `sampleSize`. Unlike dividing the original width and height by the `sampleSize` manually, calling this method allows `ImageDecoder` to round in the direction that it can do most efficiently.

Only the last call to this or `setTargetSize(int, int)` is respected.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`sampleSize` | `int`: sampling rate of the encoded image. Value is 1 or greater

### setTargetSize

    public void setTargetSize (int width,
                    int height)

Specify the size of the output `Drawable` or `Bitmap`.

By default, the output size will match the size of the encoded image, which can be retrieved from the `ImageInfo` in `onHeaderDecoded`.

This will sample or scale the output to an arbitrary size that may be smaller or larger than the encoded size.

Only the last call to this or `setTargetSampleSize(int)` is respected.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`width` | `int`: width in pixels of the output, must be greater than 0 This units of this value are pixels. Value is 1 or greater
`height` | `int`: height in pixels of the output, must be greater than 0 This units of this value are pixels. Value is 1 or greater

### setUnpremultipliedRequired

    public void setUnpremultipliedRequired (boolean unpremultipliedRequired)

Specify whether the `Bitmap` should have unpremultiplied pixels.

By default, ImageDecoder will create a `Bitmap` with premultiplied pixels, which is required for drawing with the `View` system (i.e. to a `Canvas`). Calling this method with a value of `true` will result in `decodeBitmap(ImageDecoder.Source)` returning a `Bitmap` with unpremultiplied pixels. See `Bitmap.isPremultiplied()`. This is incompatible with `decodeDrawable`; attempting to decode an unpremultiplied `Drawable` will throw an `IllegalStateException`.

Like all setters on ImageDecoder, this must be called inside `onHeaderDecoded`.

Parameters
`unpremultipliedRequired` | `boolean`

## Protected methods

### finalize

    protected void finalize ()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. A subclass overrides the `finalize` method to dispose of system resources or to perform other cleanup.

The general contract of `finalize` is that it is invoked if and when the Java™ virtual machine has determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, except as a result of an action taken by the finalization of some other object or class which is ready to be finalized. The `finalize` method may take any action, including making this object available again to other threads; the usual purpose of `finalize`, however, is to perform cleanup actions before the object is irrevocably discarded. For example, the finalize method for an object that represents an input/output connection might perform explicit I/O transactions to break the connection before the object is permanently discarded.

The `finalize` method of class `Object` performs no special action; it simply returns normally. Subclasses of `Object` may override this definition.

The Java programming language does not guarantee which thread will invoke the `finalize` method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught exception is thrown by the finalize method, the exception is ignored and finalization of that object terminates.

After the `finalize` method has been invoked for an object, no further action is taken until the Java virtual machine has again determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, including possible actions by other objects or classes which are ready to be finalized, at which point the object may be discarded.

The `finalize` method is never invoked more than once by a Java virtual machine for any given object.

Any exception thrown by the `finalize` method causes the finalization of this object to be halted, but is otherwise ignored.

Throws
`Throwable` |

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