Package com.bumptech.glide.load

Interface Transformation<T>

Type Parameters:
T - The type of the resource being transformed.
All Superinterfaces:
Key
All Known Implementing Classes:
BitmapDrawableTransformation, BitmapTransformation, CenterCrop, CenterInside, CircleCrop, DrawableTransformation, FitCenter, GifDrawableTransformation, GranularRoundedCorners, MultiTransformation, Rotate, RoundedCorners, UnitTransformation
public interface Transformation<T> extends Key
A class for performing an arbitrary transformation on a resource that implements Key.equals(Object) and Key.hashCode()} to identify the transformation in the memory cache and Key.updateDiskCacheKey(java.security.MessageDigest)} to identify the transformation in disk caches.

Using the fully qualified class name as a static final String (not Class.getName() to avoid proguard obfuscation) is an easy way to implement Key.updateDiskCacheKey(java.security.MessageDigest)} correctly. If additional arguments are required they can be passed in to the constructor of the Transformation and then used to update the MessageDigest passed in to Key.updateDiskCacheKey(MessageDigest). If arguments are primitive types, they can typically easily be serialized using ByteBuffer. String types can be serialized with String.getBytes(Charset) using the constant Key.CHARSET.

Implementations must implement Key.equals(Object) and Key.hashCode() for memory caching to work correctly.

  • Method Details

    • transform

      @NonNull Resource<T> transform(@NonNull Context context, @NonNull Resource<T> resource, int outWidth, int outHeight)
      Transforms the given resource and returns the transformed resource.

      If the original resource object is not returned, the original resource will be recycled and it's internal resources may be reused. This means it is not safe to rely on the original resource or any internal state of the original resource in any new resource that is created. Usually this shouldn't occur, but if absolutely necessary either the original resource object can be returned with modified internal state, or the data in the original resource can be copied into the transformed resource.

      If a Transformation is updated, Key.equals(Object), Key.hashCode(), and Key.updateDiskCacheKey(java.security.MessageDigest) should all change. If you're using a simple String key an easy way to do this is to append a version number to your key. Failing to do so will mean users may see images loaded from cache that had the old version of the Transformation applied. Changing the return values of those methods will ensure that the cache key has changed and therefore that any cached resources will be re-generated using the updated Transformation.

      During development you may need to either using DiskCacheStrategy.NONE or make sure Key.updateDiskCacheKey(java.security.MessageDigest) changes each time you make a change to the Transformation. Otherwise the resource you request may be loaded from disk cache and your Transformation may not be called.

      Parameters:
      context - The Application context
      resource - The resource to transform.
      outWidth - The width of the view or target the resource will be displayed in, or Target.SIZE_ORIGINAL to indicate the original resource width.
      outHeight - The height of the view or target the resource will be displayed in, or Target.SIZE_ORIGINAL to indicate the original resource height.
      Returns:
      The transformed resource.