Package com.bumptech.glide.load.resource.bitmap

Class BitmapTransformation

java.lang.Object
com.bumptech.glide.load.resource.bitmap.BitmapTransformation
All Implemented Interfaces:
Key, Transformation<Bitmap>
Direct Known Subclasses:
CenterCrop, CenterInside, CircleCrop, FitCenter, GranularRoundedCorners, Rotate, RoundedCorners
public abstract class BitmapTransformation extends Object implements Transformation<Bitmap>
A simple Transformation for transforming Bitmaps that abstracts away dealing with Resource objects for subclasses.

Use cases will look something like this: 


 public class FillSpace extends BitmapTransformation {
     private static final String ID = "com.bumptech.glide.transformations.FillSpace";
     private static final byte[] ID_BYTES = ID.getBytes(Charset.forName("UTF-8"));

     {@literal @Override}
     public Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
         if (toTransform.getWidth() == outWidth && toTransform.getHeight() == outHeight) {
             return toTransform;
         }

         return Bitmap.createScaledBitmap(toTransform, outWidth, outHeight, true);
     }

     {@literal @Override}
     public boolean equals(Object o) {
       return o instanceof FillSpace;
     }

     {@literal @Override}
     public int hashCode() {
       return ID.hashCode();
     }

     {@literal @Override}
     public void updateDiskCacheKey(MessageDigest messageDigest) {
       messageDigest.update(ID_BYTES);
     }
 }

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.

As with all Transformations, all subclasses must implement Object.equals(Object) and Object.hashCode() for memory caching to work correctly.

  • Constructor Details

    • BitmapTransformation

      public BitmapTransformation()

  • Method Details

    • transform

      @NonNull public final Resource<Bitmap> transform(@NonNull Context context, @NonNull Resource<Bitmap> resource, int outWidth, int outHeight)
      Description copied from interface: Transformation
      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.

      Specified by:
      transform in interface Transformation<Bitmap>
      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.

    • transform

      protected abstract Bitmap transform(@NonNull BitmapPool pool, @NonNull Bitmap toTransform, int outWidth, int outHeight)
      Transforms the given Bitmap based on the given dimensions and returns the transformed result.

      The provided Bitmap, toTransform, should not be recycled or returned to the pool. Glide will automatically recycle and/or reuse toTransform if the transformation returns a different Bitmap. Similarly implementations should never recycle or return Bitmaps that are returned as the result of this method. Recycling or returning the provided and/or the returned Bitmap to the pool will lead to a variety of runtime exceptions and drawing errors. See #408 for an example. If the implementation obtains and discards intermediate Bitmaps, they may safely be returned to the BitmapPool and/or recycled.

      outWidth and outHeight will never be Target.SIZE_ORIGINAL, this class converts them to be the size of the Bitmap we're going to transform before calling this method.

      Parameters:
      pool - A BitmapPool that can be used to obtain and return intermediate Bitmaps used in this transformation. For every Bitmap obtained from the pool during this transformation, a Bitmap must also be returned.
      toTransform - The Bitmap to transform.
      outWidth - The ideal width of the transformed bitmap (the transformed width does not need to match exactly).
      outHeight - The ideal height of the transformed bitmap (the transformed height does not need to match exactly).