feat: Support saving embedded images based on their hash (#19)

- This should reduce the amount of images being saved and make things go a bit faster.
- ❗ This really only works based on a "social contract", where the hashes passed to `knownHashes` are stored in `saveDirectory` & has the same `format`.
- ❗ Removed `updateConfigs()`.

Author: cyanChill

CHANGELOG.md

@@ -7,10 +7,26 @@ and this project attempts to adhere to [Semantic Versioning](https://semver.org/
 
 ## [Unreleased]
 
+### ❗ Breaking Changes
+
+- Removed `updateConfigs()` function.
+  - If you used it to specify the max size of the return base64 image, patch the package and update the `maxImgSizeMB` variable in `ArtworkParser.kt`.
+  - ❗ Things are a bit "strict" as the hashes in `knownHashes` must reflect the other specified arguments (`saveDirectory` & `format`).
+
+### 🎉 Added
+
+- New `saveHashedArtwork()` function which saves embedded artwork by their derived MD5 hash.
+  - This helps reuse previously saved artwork as you can provide an array of previously saved hashes to help us identify whether the artwork should be saved. The returned `uri` is made up of the hash.
+
 ### ⚡ Changes
 
 - Bumped AndroidX media3 to `1.10.1` from `1.9.3`.
 
+### ⚙️ Internal Changes
+
+- Refactor image saving logic.
+- Have the "Saved Artwork" strategy in the example app use `saveHashedArtwork()`.
+
 ## [3.2.1] - 2026-06-21
 
 ### 🛠️ Fixes

README.md

@@ -65,9 +65,7 @@ Formats that we can save the image as.
 function getArtwork(uri: string): Promise<string | null>;
 ```
 
-Returns a base64 string representing the embedded artwork.
-
-> **Note:** Defaults to returning up to `5 MB` of data. Can be configured with [`updateConfigs`](#updateConfigs).
+Returns a base64 string (worth up to `5 MB` of data) representing the embedded artwork.
 
 ### getBulkMetadata
 
@@ -120,15 +118,18 @@ function saveArtwork(
 
 Returns the uri of the saved artwork.
 
-> **Note:** Ignores the hard-limit of the max size of the image that can be saved.
-
-### updateConfigs
+### saveHashedArtwork
 
 ```ts
-function updateConfigs(options: ConfigOptions): Promise<void>;
+function saveHashedArtwork(
+  uri: string,
+  options?: HashedArtworkOptions
+): Promise<{ hash: string; uri: string } | null>;
 ```
 
-Update internal configuration options such as the max size of the returned base64 image.
+Returns the hash of the embedded image & uri of the saved artwork.
+
+> **Note:** It will work as "expected" given that everything follows the same "social contract", as in `knownHashes` contain hashes based on the same configuration passed to this function call.
 
 ## Types
 
@@ -170,19 +171,32 @@ type BulkMetadata<TKeys extends MediaMetadataPublicFields> = {
 
 Structure returned when using `getBulkMetadata`.
 
-### ConfigOptions
+### HashedArtworkOptions
 
 ```ts
-type ConfigOptions = {
+type HashedArtworkOptions = {
+  /**
+   * A value in the range `0.0` - `1.0` specifying the quality of the resulting image.
+   * - Defaults to `1`.
+   */
+  compress?: number;
+  /**
+   * Specifies the format the image will be saved in.
+   * - Defaults to `SaveFormat.JPEG`.
+   */
+  format?: SaveFormat;
+  /** Directory where we want to save the hashed image. The file name will be the hash. */
+  saveDirectory: string;
   /**
-   * Size of the returned base64 image in MB.
-   * - Defaults to `5`.
+   * An array of known MD5 hashes formatted as a 32-character hexadecimal string
+   * which are stored in `saveDirectory` and is of the same format as what we
+   * pass for the `format` option.
    */
-  maxImageSizeMB?: number | null;
+  knownHashes: string[];
 };
 ```
 
-Configuration options we can set to modify the behavior of the package.
+Options to change the behavior of `saveHashedArtwork`.
 
 ### MediaMetadata
 

android/src/main/java/com/cyanchill/missingcore/metadataretriever/models/ArtworkOptions.kt

@@ -3,31 +3,58 @@ package com.cyanchill.missingcore.metadataretriever.models
 import android.graphics.Bitmap
 import android.net.Uri
 import android.os.Bundle
+import com.cyanchill.missingcore.metadataretriever.utils.RequiredArgumentException
 import com.facebook.react.bridge.Arguments
 import com.facebook.react.bridge.ReadableMap
+import java.io.File
 
-class ArtworkOptions(options: ReadableMap) {
-  /** If we want to return the artwork as a base64 string. */
-  val asBase64: Boolean
-
-  /** A value in the range `0.0` - `1.0` specifying the quality of the resulting image. */
-  val compress: Double
-  /** Specifies the format the image will be saved in. */
-  val format: ImageFormat
-  /** Location where we want to save the image. */
-  val saveUri: String?
-
-  init {
-    val optionsBundle = Arguments.toBundle(options) as Bundle
-    asBase64 = optionsBundle.getBoolean("base64")
+data class ArtworkOptions(
+  /** If the image should be returned as a base64 string. */
+  val base64: Boolean = false,
+  /** Value in the range of `0.0` - `1.0` specifying the quality of the resulting image. */
+  val compress: Double = 1.0,
+  /** Format the image will be saved in. */
+  val format: ImageFormat = ImageFormat.JPEG,
+  /**
+   * [Only for Non-Image Hashing Strategy]
+   * "Location" artwork will be saved to (includes file name + extension).
+   */
+  val saveUri: String?,
+  /**
+   * [Only for Image Hashing Strategy]
+   * The directory the file will be saved to.
+   */
+  val saveDirectory: String?,
+  /**
+   * [Only for Image Hashing Strategy]
+   * A list of image hashes inside of `saveDirectory` with the format specified by `format`.
+   */
+  val knownHashes: ArrayList<String>?
+) {
+  fun withGeneratedSaveUri(hash: String): ArtworkOptions {
+    if (saveDirectory == null) {
+      throw RequiredArgumentException("withGeneratedSaveUri", "saveDirectory")
+    }
+    return this.copy(
+      saveUri = "${saveDirectory}${File.separator}$hash${format.fileExtension}",
+    )
+  }
 
-    compress = if (optionsBundle.containsKey("compress")) optionsBundle.getDouble("compress") else 1.0
-    // Default format to JPEG if it's not provided.
-    format = ImageFormat.fromCode(optionsBundle.getString("format")) ?: ImageFormat.JPEG
+  companion object {
+    fun fromReadableMap(options: ReadableMap): ArtworkOptions {
+      val optionsBundle = Arguments.toBundle(options) as Bundle
 
-    // Remove `file://` in `saveUri` if provided.
-    val uri = optionsBundle.getString("saveUri")
-    saveUri = if (uri != null) Uri.parse(uri).path else null
+      return ArtworkOptions(
+        optionsBundle.getBoolean("base64"),
+        if (optionsBundle.containsKey("compress")) {
+          optionsBundle.getDouble("compress").coerceIn(0.0, 1.0)
+        } else 1.0,
+        ImageFormat.fromCode(optionsBundle.getString("format")) ?: ImageFormat.JPEG,
+        optionsBundle.getString("saveUri")?.let { Uri.parse(it).path },
+        optionsBundle.getString("saveDirectory")?.let { Uri.parse(it).path },
+        optionsBundle.getStringArrayList("knownHashes"),
+      )
+    }
   }
 }
 

android/src/main/java/com/cyanchill/missingcore/metadataretriever/modules/APIConfigs.kt

@@ -0,0 +1,152 @@
+package com.cyanchill.missingcore.metadataretriever.modules
+
+import android.graphics.BitmapFactory
+import android.media.MediaMetadataRetriever
+import android.net.Uri
+import android.util.Base64
+import androidx.annotation.OptIn
+import androidx.media3.common.MediaMetadata
+import androidx.media3.common.Metadata
+import androidx.media3.common.MimeTypes
+import androidx.media3.common.util.UnstableApi
+import com.cyanchill.missingcore.metadataretriever.models.ArtworkOptions
+import com.cyanchill.missingcore.metadataretriever.utils.Normalization
+import com.facebook.react.bridge.ReactApplicationContext
+import java.io.File
+import java.io.FileOutputStream
+import java.net.URLConnection
+import java.security.MessageDigest
+import java.util.UUID
+
+data class ArtworkSignature(
+  val hash: String,
+  val bytes: ByteArray,
+) {
+  companion object {
+    fun fromBytes(bytes: ByteArray?): ArtworkSignature? {
+      if (bytes == null) return null
+      return ArtworkSignature(bytes.toMd5Hex(), bytes)
+    }
+  }
+}
+
+@OptIn(UnstableApi::class)
+class ArtworkParser(reactContext: ReactApplicationContext) {
+  private val saveDirectory = "${reactContext.cacheDir.absolutePath}${File.separator}MetadataRetriever"
+
+  /** Create `saveDirectory` if it doesn't exist. */
+  init {
+    try {
+      val directory = File(saveDirectory)
+      if (!directory.exists()) directory.mkdirs()
+    } catch (e: Exception) {}
+  }
+
+  //#region [Extractor]
+  fun extractArtwork(uri: String, metadataList: List<Metadata>): ArtworkSignature? {
+    val isFLAC = uri.endsWith(".flac") || uri.endsWith(".m4a") || uri.endsWith(".mp4")
+
+    // We'll want to return the image designated as "Cover (front)", otherwise return first image found.
+    var coverImage: ArtworkSignature? = null
+    var backupImage: ArtworkSignature? = null
+
+    // Fallback to `MediaMetadataRetriever` if we find nothing with `MetadataRetriever` or with
+    // flac/mp4/m4a files due to artwork not being parsed correctly.
+    //  - https://github.com/MissingCore/Music/issues/432
+    if (metadataList.isEmpty() || isFLAC) {
+      val mmrMetadata = MediaMetadataRetriever()
+      try {
+        mmrMetadata.setDataSource(Normalization.getSafeUri(uri))
+        coverImage = ArtworkSignature.fromBytes(mmrMetadata.embeddedPicture)
+      } finally {
+        mmrMetadata.release()
+      }
+    }
+
+    for (metadataItem in metadataList) {
+      val mediaMetadata = MediaMetadata.Builder()
+        .populateFromMetadata(metadataItem)
+        .build()
+
+      when (mediaMetadata.artworkDataType) {
+        // "Cover (front)" Picture Type
+        MediaMetadata.PICTURE_TYPE_FRONT_COVER -> {
+          coverImage = ArtworkSignature.fromBytes(mediaMetadata.artworkData)
+        }
+        // Fallback to 1st image found.
+        else -> {
+          if (backupImage == null) {
+            backupImage = ArtworkSignature.fromBytes(mediaMetadata.artworkData)
+          }
+        }
+      }
+
+      if (coverImage !== null) break
+    }
+
+    return coverImage ?: backupImage
+  }
+  //#endregion
+
+  //#region ["Formatters"]
+  fun asBase64(bytes: ByteArray): String? {
+    if (!isBase64Convertible(bytes)) return null
+    return "data:${getMimeType(bytes)};base64,${Base64.encodeToString(bytes, Base64.NO_WRAP)}"
+  }
+
+  fun asFile(bytes: ByteArray, options: ArtworkOptions): String? {
+    try {
+      // Generate path to save image if we didn't provide one.
+      val imgUri = options.saveUri ?: "$saveDirectory${File.separator}${UUID.randomUUID()}${options.format.fileExtension}"
+      val bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
+      FileOutputStream(imgUri).use { fos ->
+        bitmap.compress(
+          options.format.compressFormat,
+          (options.compress * 100).toInt(),
+          fos,
+        )
+        fos.flush()
+      }
+      return formatUri(imgUri)
+    } catch (e: Exception) {
+      return null
+    }
+  }
+
+  /** Sanitizes URI with Android's URI util. */
+  fun formatUri(uri: String): String {
+    return Uri.fromFile(File(uri)).toString()
+  }
+  //#endregion
+
+  //#region [Helpers]
+  /** Determines mimetype from bytes. */
+  private fun getMimeType(bytes: ByteArray): String? {
+    return URLConnection.guessContentTypeFromStream(bytes.inputStream())?.let {
+      MimeTypes.normalizeMimeType(it)
+    }
+  }
+
+  /** Determines if ByteArray can be converted as a base64 string based on our constraints. */
+  private fun isBase64Convertible(bytes: ByteArray?): Boolean {
+    if (bytes == null) return false
+    // Ensure the mimeType we get is defined and is for an image.
+    if (!MimeTypes.isImage(getMimeType(bytes))) return false
+    // Convert max MB to bytes. We take 3/4 of the max MB as converting a byte array to a base64
+    // string causes a 33% increase in size.
+    val maxSizeBytes = maxImgSizeMB * 0.75 * 1024 * 1024
+    return bytes.size <= maxSizeBytes
+  }
+  //#endregion
+
+  companion object {
+    var maxImgSizeMB: Double = 5.0
+  }
+}
+
+/** Get an MD5 hash as a 32-character hexadecimal string. */
+fun ByteArray.toMd5Hex(): String {
+  val md = MessageDigest.getInstance("MD5")
+  val digest = md.digest(this)
+  return digest.joinToString("") { "%02x".format(it) }
+}