APNG identification

CHANGELOG.md

@@ -7,7 +7,7 @@ All notable changes to this project will be documented in this file.
 ### Added
 
 - option to set the Tags page as home
-- support for animated PNG
+- support for animated PNG (requires rescan)
 - Info: added day filter with item date
 - Widget: option to update image on tap
 - Slideshow / Screen saver: option for random transition

android/app/src/main/AndroidManifest.xml

@@ -301,7 +301,7 @@ This change eventually prevents building the app with Flutter v3.7.11.
         <meta-data
             android:name="flutterEmbedding"
             android:value="2" />
-        <!-- as of Flutter v3.7.7, background blur yields black screen with Impeller -->
+        <!-- as of Flutter v3.10.1, Impeller badly renders text, fails to render videos, and crashes with Google Maps -->
         <meta-data
             android:name="io.flutter.embedding.android.EnableImpeller"
             android:value="false" />

android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/MetadataFetchHandler.kt

@@ -75,6 +75,7 @@ import deckers.thibault.aves.metadata.metadataextractor.Helper.getSafeInt
 import deckers.thibault.aves.metadata.metadataextractor.Helper.getSafeRational
 import deckers.thibault.aves.metadata.metadataextractor.Helper.getSafeString
 import deckers.thibault.aves.metadata.metadataextractor.Helper.isPngTextDir
+import deckers.thibault.aves.metadata.metadataextractor.PngActlDirectory
 import deckers.thibault.aves.model.FieldMap
 import deckers.thibault.aves.utils.ContextUtils.queryContentPropValue
 import deckers.thibault.aves.utils.LogUtils
@@ -657,6 +658,11 @@ class MetadataFetchHandler(private val context: Context) : MethodCallHandler {
                                     }
                                 }
                             }
+
+                            // identification of animated PNG
+                            if (metadata.containsDirectoryOfType(PngActlDirectory::class.java)) {
+                                flags = flags or MASK_IS_ANIMATED
+                            }
                         }
 
                         MimeTypes.GIF -> {

android/app/src/main/kotlin/deckers/thibault/aves/metadata/metadataextractor/PngActlDirectory.kt

@@ -0,0 +1,22 @@
+package deckers.thibault.aves.metadata.metadataextractor
+import com.drew.imaging.png.PngChunkType
+import com.drew.metadata.png.PngDirectory
+
+class PngActlDirectory : PngDirectory(chunkType) {
+    override fun getTagNameMap(): HashMap<Int, String> {
+        return tagNames
+    }
+
+    companion object {
+        val chunkType = PngChunkType("acTL")
+
+        // tags should be distinct from those already defined in `PngDirectory`
+        const val TAG_NUM_FRAMES = 101
+        const val TAG_NUM_PLAYS = 102
+
+        private val tagNames = hashMapOf(
+            TAG_NUM_FRAMES to "Number Of Frames",
+            TAG_NUM_PLAYS to "Number Of Plays",
+        )
+    }
+}

android/app/src/main/kotlin/deckers/thibault/aves/metadata/metadataextractor/SafePngMetadataReader.kt

@@ -34,9 +34,10 @@ import java.io.InputStream
 import java.util.zip.InflaterInputStream
 import java.util.zip.ZipException
 
-// adapted from `PngMetadataReader` to prevent OOM from reading large chunks
+// adapted from `PngMetadataReader` to:
-// as of `metadata-extractor` v2.18.0, there is no way to customize the reader
+// - prevent OOM from reading large chunks. As of `metadata-extractor` v2.18.0, there is no way to customize the reader
-// without copying `desiredChunkTypes` and the whole `processChunk` function
+// without copying `desiredChunkTypes` and the whole `processChunk` function.
+// - parse `acTL` chunk to identify animated PNGs.
 object SafePngMetadataReader {
     private val LOG_TAG = LogUtils.createTag<SafePngMetadataReader>()
 
@@ -60,6 +61,7 @@ object SafePngMetadataReader {
         PngChunkType.pHYs,
         PngChunkType.sBIT,
         PngChunkType.eXIf,
+        PngActlDirectory.chunkType,
     )
 
     @Throws(IOException::class, PngProcessingException::class)
@@ -99,6 +101,21 @@ object SafePngMetadataReader {
             directory.setInt(PngDirectory.TAG_FILTER_METHOD, header.filterMethod.toInt())
             directory.setInt(PngDirectory.TAG_INTERLACE_METHOD, header.interlaceMethod.toInt())
             metadata.addDirectory(directory)
+            // TLAD insert start
+        } else if (chunkType == PngActlDirectory.chunkType) {
+            if (bytes.size != 8) {
+                throw PngProcessingException("Invalid number of bytes")
+            }
+            val reader = SequentialByteArrayReader(bytes)
+            try {
+                metadata.addDirectory(PngActlDirectory().apply {
+                    setInt(PngActlDirectory.TAG_NUM_FRAMES, reader.int32)
+                    setInt(PngActlDirectory.TAG_NUM_PLAYS, reader.int32)
+                })
+            } catch (ex: IOException) {
+                throw PngProcessingException(ex)
+            }
+            // TLAD insert end
         } else if (chunkType == PngChunkType.PLTE) {
             val directory = PngDirectory(PngChunkType.PLTE)
             directory.setInt(PngDirectory.TAG_PALETTE_SIZE, bytes.size / 3)