Fix thumbnails: use MediaStore thumbnail DB instead of partial file pull
Previous approach pulled first 64KB of JPEG which produces a truncated file Skia cannot decode. New approach: 1. Query MediaStore content:// URI to find the pre-generated thumbnail path for each photo (Android generates these automatically) 2. Pull just the thumbnail file (~20-50KB vs 3-5MB full file) 3. Cache locally — subsequent views are instant Falls back gracefully (placeholder icon) if MediaStore query fails.
This commit is contained in:
Kyle Bolen
@@ -181,17 +181,20 @@ private fun PhotoCell(
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val date = photo.dateTaken.atZone(ZoneId.systemDefault()).toLocalDate()
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val dateStr = date.format(DateTimeFormatter.ofPattern("MMM d"))
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// Load thumbnail asynchronously
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// Load thumbnail asynchronously — limited concurrency to avoid overwhelming ADB
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var thumbnail by remember(photo.devicePath) { mutableStateOf<ImageBitmap?>(null) }
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var failed by remember(photo.devicePath) { mutableStateOf(false) }
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LaunchedEffect(photo.devicePath) {
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if (device?.adbSerial != null) {
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if (device?.adbSerial != null && !failed) {
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val bytes = withContext(Dispatchers.IO) {
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ThumbnailCache.get(adbBin, device.adbSerial, photo.devicePath, photo.filename)
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}
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if (bytes != null) {
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runCatching {
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thumbnail = Image.makeFromEncoded(bytes).toComposeImageBitmap()
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}
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}.onFailure { failed = true }
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} else {
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failed = true
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}
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}
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}
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@@ -1,7 +1,6 @@
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package com.bolenpad.photophetch.util
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import org.slf4j.LoggerFactory
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import java.io.ByteArrayOutputStream
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import java.nio.file.Files
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import java.nio.file.Path
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import java.nio.file.Paths
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@@ -9,21 +8,26 @@ import kotlin.io.path.createDirectories
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import kotlin.io.path.exists
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/**
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* Pulls and caches small JPEG thumbnails from an Android device via ADB.
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* Retrieves JPEG thumbnails from an Android device using the MediaStore
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* thumbnail database via `adb shell content query` + thumbnail URI pull.
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*
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* Strategy: pull the first 64KB of each JPEG — enough to contain the
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* embedded EXIF thumbnail (typically 10-15KB). The partial file is cached
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* locally so repeated renders don't re-hit the device.
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* Android pre-generates thumbnails at ~512px for every photo in the gallery.
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* These live in /sdcard/Android/data/com.android.providers.media/... or are
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* accessible via content://media/external/images/thumbnails.
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*
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* Cache location: ~/.photophetch/thumbcache/<serial>/<filename_hash>.jpg
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* We use `adb shell content query` to find the thumbnail path for a given
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* media file, then `adb pull` to fetch just the thumbnail (~20-50KB vs 3-5MB
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* for the full file).
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*
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* Cache location: ~/.photophetch/thumbcache/<serial>/<hash>.jpg
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*/
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object ThumbnailCache {
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private val log = LoggerFactory.getLogger(ThumbnailCache::class.java)
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private val cacheRoot: Path = Paths.get(System.getProperty("user.home"), ".photophetch", "thumbcache")
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/**
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* Returns raw JPEG bytes for the thumbnail, pulling from device if not cached.
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* Returns null if the pull failed or the file is a video.
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* Returns raw JPEG bytes for the thumbnail.
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* Returns null if unavailable (video, or MediaStore lookup failed).
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*/
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fun get(
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adbBin: String,
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@@ -32,46 +36,75 @@ object ThumbnailCache {
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filename: String,
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): ByteArray? {
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val ext = filename.substringAfterLast(".", "").lowercase()
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if (ext in setOf("mp4", "mov", "3gp", "avi")) return null // no thumb for video
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if (ext in setOf("mp4", "mov", "3gp", "avi")) return null
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val cacheDir = cacheRoot.resolve(serial)
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if (!cacheDir.exists()) cacheDir.createDirectories()
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val cacheKey = devicePath.hashCode().toString(16)
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val cacheKey = (serial + devicePath).hashCode().toString(16)
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val cachePath = cacheDir.resolve("$cacheKey.jpg")
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if (cachePath.exists()) {
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if (cachePath.exists() && cachePath.toFile().length() > 0) {
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return try { Files.readAllBytes(cachePath) } catch (_: Exception) { null }
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}
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return try {
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// Pull first 65536 bytes (enough for EXIF thumbnail in most JPEGs)
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val process = ProcessBuilder(
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adbBin, "-s", serial,
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"exec-out",
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"dd", "if=$devicePath", "bs=65536", "count=1", "2>/dev/null"
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)
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.redirectErrorStream(false)
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.start()
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// Step 1: Find the media _id for this file via MediaStore
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val mediaId = queryMediaId(adbBin, serial, devicePath) ?: return null
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val bytes = process.inputStream.readBytes()
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// Step 2: Get the thumbnail path for this media_id
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val thumbPath = queryThumbnailPath(adbBin, serial, mediaId) ?: return null
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// Step 3: Pull just the thumbnail file (~20-50KB)
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val process = ProcessBuilder(adbBin, "-s", serial, "pull", thumbPath, cachePath.toString())
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.redirectErrorStream(true)
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.start()
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process.inputStream.readBytes()
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process.waitFor()
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if (bytes.isNotEmpty()) {
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Files.write(cachePath, bytes)
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bytes
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if (cachePath.exists() && cachePath.toFile().length() > 0) {
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Files.readAllBytes(cachePath)
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} else null
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} catch (e: Exception) {
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log.debug("Thumbnail pull failed for $filename: ${e.message}")
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log.debug("Thumbnail lookup failed for $filename: ${e.message}")
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null
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}
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}
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/** Clear the entire cache for a device (call after import session). */
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private fun queryMediaId(adbBin: String, serial: String, devicePath: String): String? {
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// Query MediaStore for the _id of the file at this path
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val output = runAdb(
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adbBin, serial,
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"shell", "content", "query",
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"--uri", "content://media/external/images/media",
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"--projection", "_id",
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"--where", "_data='$devicePath'"
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)
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// Output: "Row: 0 _id=12345"
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return Regex("_id=(\\d+)").find(output)?.groupValues?.getOrNull(1)
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}
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private fun queryThumbnailPath(adbBin: String, serial: String, mediaId: String): String? {
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val output = runAdb(
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adbBin, serial,
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"shell", "content", "query",
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"--uri", "content://media/external/images/thumbnails",
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"--projection", "_data",
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"--where", "image_id=$mediaId"
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)
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// Output: "Row: 0 _data=/sdcard/.thumbnails/12345.jpg"
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return Regex("_data=([^\\s]+)").find(output)?.groupValues?.getOrNull(1)
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}
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private fun runAdb(adbBin: String, serial: String, vararg args: String): String {
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val cmd = listOf(adbBin, "-s", serial) + args.toList()
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val process = ProcessBuilder(cmd).redirectErrorStream(true).start()
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val output = process.inputStream.bufferedReader().readText()
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process.waitFor()
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return output
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}
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fun clearForDevice(serial: String) {
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val cacheDir = cacheRoot.resolve(serial)
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if (cacheDir.exists()) {
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cacheDir.toFile().deleteRecursively()
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}
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cacheRoot.resolve(serial).toFile().deleteRecursively()
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}
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}
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