What's New in PhotoLens

All notable changes to PhotoLens are documented here. Versions follow Semantic Versioning.

---

[1.2.0] — 2026-05-10

Theme: Multi-photo chat, rich sound design, secure vault, full accessibility polish, and a settings overhaul.

New Features

Multi-Photo Chat (URI Preview)

• Attach multiple photos in a single chat session — add up to N photos from your gallery or camera directly into a conversation
• Horizontal photo strip above the message list shows each attached image with a remove button
• Camera capture within AskScreen — take a photo on the spot and send it immediately to the AI
• Photo picker integration in AskScreen, same flow as HomeScreen's "New Photo" sheet

Sound Design

• Five ambient audio cues — processing loop, reply ding, success chime, page turn, and delete sweep; all non-blocking and run off the main thread
• Haptic feedback with configurable sensitivity (0–100%)
• All sounds independently togglable per-event in Settings

Secure Vault (Collections)

• Per-collection security — lock any album behind biometric or a custom password; vault photos are physically moved to filesDir/secure_photos, not merely hidden
• Vault passwords hashed with SHA-256 + 16-byte random salt + 10,000 iterations; raw password is never written to disk
• Constant-time password comparison to prevent timing attacks
• Security progress bottom sheet with animated progress bar during vault operations
• showSecureCollectionsInList setting to control vault visibility in the Collections tab

TTS Reader — Complete Rewrite

• ReaderComponent embedded in every chat bubble and OCR result sheet
• Reading modes: Characters, Words, Sentences, Paragraphs, Lines — switchable on the fly
• Prev / Play-Pause / Next segment controls with TalkBack-labelled state
• autoplayOnLoad and stopOnBackground lifecycle hooks
• Non-blocking architecture: all TTS work runs on Dispatchers.IO; UI thread is never held
• Voice selection, pitch, rate, and engine configurable in Settings

Full Settings Screen

• Appearance & Gallery — theme (System/Light/Dark/AMOLED), accent color (6 options + Dynamic Material You), startup screen selection, grid density (2–5 columns), keep screen awake toggle
• Advanced Filters — saved per-session; min/max width & height, date range picker, MIME type chip filter
• AI Tuning — temperature, top-P, top-K sliders; response length (Brief / Balanced / Detailed / Extremely Detailed); thinking budget; streaming toggle; auto-generate descriptions
• Sound & Vibration — per-event toggles for all five sound events plus haptic sensitivity slider
• Security — biometric vs. custom-password vault mode; change vault password; disable vault with confirmation dialog
• TTS — engine picker (all installed TTS engines), language picker (50+ languages from languages.json), pitch, rate, voice selection
• Secure Sharing — strip GPS and full EXIF metadata before sharing
• Language — AI response language picker with human-readable names (13+ languages from languages.json)

Onboarding Flow

• 5-page pager onboarding on first launch, fully TalkBack-navigable
• Pages: Welcome, Smart Gallery, AI Features, Accessibility, Privacy & Security
• Model download prompt triggered automatically after onboarding if no model is present

ReasoningBlock Component

• Expandable "chain-of-thought" block in chat bubbles and photo description — shows the model's internal reasoning before the final answer
• Collapsed by default; animates open/close with a chevron

Markdown Renderer

• Full MarkdownContent composable with no external dependency
• Supports: headings (H1–H4), bold, italic, bold-italic, inline code, code blocks, blockquotes, unordered lists, ordered lists, horizontal rules, links (tappable)

About, Help & Support, Privacy, Terms screens

• All rendered via the generic MarkdownScreen composable backed by res/raw/*.md files

Improvements

• Smart Collections empty state — contextual message depending on whether any AI descriptions exist; CTA button to go to Settings when descriptions haven't been generated yet
• Photo detail screen — pinch-to-zoom + two-finger rotate with spring-back animation; rotation persisted per photo; zoom/rotation reset on navigation
• Bulk operations — add to favorites, generate descriptions, recognize text, share, add to collection, delete — all from the selection top bar
• OCR bottom sheet — TTS reader embedded; copy + share buttons; streaming progress indicator
• ListScreen — collection/album detail with the same sort/filter/bulk-select as HomeScreen
• Session memory optimization — "Preparing AI Environment" overlay with polite live-region announcement so TalkBack users know when chat is ready
• Scroll-to-bottom FAB in AskScreen — appears when the user scrolls up; animates in/out with fade + scale
• Chat export — copy all messages to clipboard or share as plain text
• Message regeneration — re-run the last AI turn from the same message index
• SpeechRecognizer lifecycle fix — recognizer is properly destroyed when AskScreen leaves composition, preventing a native listener leak after back-navigation

Bug Fixes

• GemmaAdapter.processResponse now builds JSON with JSONObject/JSONArray instead of string interpolation — fixes crashes on model output containing quotes, backslashes, or newlines
• Vault password stored as SHA-256 hash + salt rather than plaintext — security fix
• LiteRtLmManager single-session constraint: properly prevents a second createConversation while one is already open; description session re-opens when chat session ends
• TtsManager no longer blocks the UI thread — all TTS calls post to Main via withContext(Dispatchers.Main) from Dispatchers.IO
• Photo URI resolution handles both file:// scheme and content:// URIs via ParcelFileDescriptor /proc/self/fd trick

---

[1.1.0] — 2026-04-14

Theme: Multi-model architecture with model-specific adapters for full control over tokenisation strategy.

New Features

Multi-Model Architecture

• ModelAdapter interface — pluggable adapter per model that controls system instruction, content building, conversation config creation, and response post-processing
• GemmaAdapter — dedicated adapter for Gemma 4 models; implements tool-call structured JSON response parsing with proper escaping
• FastVlmAdapter — adapter skeleton for FastVLM-class models with different tokenisation strategy
• Models defined in assets/models.json — adapter field determines which adapter is instantiated at runtime

Model-Specific Behaviour

• getSystemInstruction() — per-adapter system prompt customisation
• buildAnalysisContent() — per-adapter content construction for photo analysis turns
• buildAskContent() — per-adapter content construction for interactive chat turns
• createConversationConfig() — per-adapter ConversationConfig including sampler config and tool registration
• processResponse() — per-adapter post-processing of raw model output and tool call arguments

JsonModel Data Class

• New fields: adapter (string, selects adapter class), preferredBackend (overrides global CPU/GPU), toolCall (boolean), memoryMinRequired, memoryRecommended
• ModelStatus wraps JsonModel with download state, progress bytes, speed, ETA, and error message

Models Manager

• Redesigned ModelConfigScreen — card-per-model layout showing size, RAM requirements, download status, speed, ETA
• Download/cancel/delete controls per model; active model shown with a checkmark badge
• Model switch triggers full LiteRtLmManager.shutdown() + re-init to ensure correct adapter is loaded

Improvements

• LiteRtLmManager session mode enum (DESCRIPTION / CHAT) replaces boolean flag — clearer invariants and easier to extend
• Speculative decoding enabled via ExperimentalFlags.enableSpeculativeDecoding = true for faster token generation
• ModelDownloadService — foreground service with resume support via HTTP Range header; progress reported via SharedFlow

Bug Fixes

• ModelAdapter.processResponse with tool calls no longer crashes on model output that embeds special JSON characters — replaced string interpolation with JSONObject.put() throughout

---

[1.0.0] — 2026-04-14

Theme: Initial release — on-device AI photo gallery built for accessibility.

New Features

Core AI Integration

• On-device AI inference via Google AI Edge LiteRT-LM with Gemma 4 multimodal model
• Natural language photo descriptions — full sentences generated by Gemma 4 locally, no internet
• Interactive Ask Mode — streaming chat interface to ask any question about a photo
• Smart categorisation — photos automatically grouped into Nature, People, Food, Documents, Travel, Architecture, Pets, Sports via tool calls
• OCR / text recognition — extract text from any image using the same on-device model
• Thinking Mode — chain-of-thought reasoning visible before the final answer
• Multilingual output — 13 languages selectable for AI response language

Gallery & Navigation

• Grid and list view — togglable; grid supports 2–5 columns
• Date-grouped photo timeline with sticky headers
• Local Albums via Android MediaStore
• Smart Collections — dynamic albums built from AI-generated categories
• Favorites — star any photo; dedicated Favorites tab
• Bottom navigation: Photos / Collections / Favorites
• Full-screen photo detail with share, favorite, rotate, more-menu

Privacy & Security

• Zero cloud processing — all AI runs on-device GPU/CPU/NPU
• No analytics, no telemetry, no account required
• Secure Vault foundation — architecture for secure collections in place

Accessibility Foundation

• Full TalkBack semantic labelling on every UI element
• WCAG 2.1 Level AA — high contrast, generous touch targets, predictable navigation
• Live regions for progress announcements
• Voice input for Ask Mode
• Built-in TTS with segment-based reading controls

Model Management

• Foreground download service for model files (~2.4 GB)
• Progress tracking with speed and ETA
• GPU / CPU backend selection

Settings

• AI backend (GPU / CPU), temperature, response language
• Basic gallery preferences (view mode, grid columns, sort order)

Other Screens

• About, Help & Support — Markdown-rendered
• Privacy Policy and Terms of Use — in-app Markdown

Technical Foundation

• MVVM + Repository pattern; single source of truth in PhotoRepository
• Jetpack Compose + Material 3 throughout
• Hilt dependency injection
• Room v9 database for photo metadata and description state
• DataStore for persistent preferences
• Coil for image loading with HEIC→JPEG auto-conversion

---

For the full feature list, see features.md.