com.bumptech.glide.load.Transformation Maven / Gradle / Ivy
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package com.bumptech.glide.load;
import android.content.Context;
import androidx.annotation.NonNull;
import com.bumptech.glide.load.engine.Resource;
import java.nio.charset.Charset;
import java.security.MessageDigest;
/**
* A class for performing an arbitrary transformation on a resource that implements {@link
* #equals(Object)} and {@link #hashCode()}} to identify the transformation in the memory cache and
* {@link #updateDiskCacheKey(java.security.MessageDigest)}} to identify the transformation in disk
* caches.
*
* Using the fully qualified class name as a static final {@link String} (not {@link
* Class#getName()} to avoid proguard obfuscation) is an easy way to implement {@link
* #updateDiskCacheKey(java.security.MessageDigest)}} correctly. If additional arguments are
* required they can be passed in to the constructor of the {@code Transformation} and then used to
* update the {@link java.security.MessageDigest} passed in to {@link
* #updateDiskCacheKey(MessageDigest)}. If arguments are primitive types, they can typically easily
* be serialized using {@link java.nio.ByteBuffer}. {@link String} types can be serialized with
* {@link String#getBytes(Charset)} using the constant {@link #CHARSET}.
*
*
Implementations must implement {@link #equals(Object)} and {@link #hashCode()} for
* memory caching to work correctly.
*
* @param The type of the resource being transformed.
*/
public interface Transformation extends Key {
/**
* 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, {@link #equals(Object)}, {@link #hashCode()}, and {@link
* #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 {@link
* com.bumptech.glide.load.engine.DiskCacheStrategy#NONE} or make sure {@link
* #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.
*
* @param context The Application context
* @param resource The resource to transform.
* @param outWidth The width of the view or target the resource will be displayed in, or {@link
* com.bumptech.glide.request.target.Target#SIZE_ORIGINAL} to indicate the original resource
* width.
* @param outHeight The height of the view or target the resource will be displayed in, or {@link
* com.bumptech.glide.request.target.Target#SIZE_ORIGINAL} to indicate the original resource
* height.
* @return The transformed resource.
*/
@NonNull
Resource transform(
@NonNull Context context, @NonNull Resource resource, int outWidth, int outHeight);
}