Patryk is available for hire
Hire PatrykPatryk Zoltowski
Verified Expert in Engineering
iOS Developer
Torun, Poland
Toptal member since December 3, 2021
Bio
Patryk is a digital nomad with eight years of experience as a software developer and six years as a mobile developer. He specializes in native iOS apps, but his interests include mobile applications, image processing, augmented reality, and signal processing. Patryk released a Peek Calendar, a successful application featured by Apple and numerous tech blogs.
Portfolio
Eclo, Inc.
iOS, TrueDepth Camera, AVFoundation, Metal, Point Clouds, OpenCV, ARKit...
Mohammed Aldamer
Computer Vision, You Only Look Once (YOLO), Mobile Development, iOS...
Fogale Optique SAS
iOS, iOS Camera, Camera API, Video Streaming, Core ML, Streaming, SwiftUI...
Experience
- iOS - 14 years
- Objective-C - 10 years
- Swift - 10 years
- Python - 4 years
- Camera API - 4 years
- OpenCV - 3 years
- Core ML - 2 years
- Object Detection - 1 year
Preferred Environment
MacOS, iOS, WatchOS, Swift, Objective-C, Xcode, Python, OpenCV, Slack, Git
The most amazing...
...application I've co-designed and fully developed is Peek Calendar, featured by Apple and many tech blogs.
Work Experience
iOS Developer
2022 - PRESENT
Eclo, Inc.
- Developed from scratch iOS application that scans foot in real-time and creates 3D mesh model using iPhone 3D camera and stitched point clouds.
- Proposed and co-authored a unique algorithm that fuses IMU sensor data with a depth map and color video stream, resulting in a patent application.
- Implemented and proposed a unique design solution that improved user experience and conversion rate.
Technologies: iOS, TrueDepth Camera, AVFoundation, Metal, Point Clouds, OpenCV, ARKit, TensorFlow, Core ML, AudioKit, C++, Python, Core Image, Image Manipulation, REST, iOS Video, Augmented Reality (AR), Machine Learning, API Integration, APIs, Integration, SwiftUI, Firebase, Amazon S3 (AWS S3), Algorithms, NumPy, SciPy, Artificial Intelligence (AI), Amazon Web Services (AWS), AI Integration, Mobile Development, LiDAR, Object Detection, You Only Look Once (YOLO), Apple Vision Framework, TensorFlow Lite, App Store, Back-end, App Store Acceptance Process, RESTFul APIs, FAISS, Camera API, iOS Camera, Rerun, Computer Vision, Image Processing, Full-stack, Video Editing, Node.js, WiFi, Authentication, iOS App Development, Cloud Storage, Mobile App Development, QR Codes, Audio, Audio Processing, Video & Audio Processing, Video Processing, Sensor Fusion, Offline-first Development, Software, Sensor Data, Processing & Threading
Computer Vision Expert
2025 - 2025
Mohammed Aldamer
- Assembled a training dataset that was the best of the client's use case across datasets from the Roboflow universe and developed a synthetic dataset using BlenderProc.
- Cleaned object detection labels in the mislabelled dataset using a combination of custom card object detection trained on the Object365 dataset and SAM2, manually corrected labels in Roboflow, and classification of cropped ROI using Gemini 2.0 Flash.
- Compared and trained a few object detection models, exported them to Core ML, and tuned the performance. Models such as: YOLOv11, YOLOv9, YOLO-NAS, RF-DETR, RT-DETR.
- Helped recommend the best pipeline setup for client use of inference on iPhone, including custom AVFoundation camera format, fps, ISO, white balance, exposure, camera orientation, and recommended scene setup.
- Implemented multi-stage object detection setup in Python and rerun, including motion detection and tracking (OpenCV), background segmentation (ObjectCV), camera image rectification (OpenCV, chessboard, aruco), and card detection (1 and 52 classes).
- Investigated Apple VisionAPI models for background segmentation, tracking, optical flow, and Create ML models.
Technologies: Computer Vision, You Only Look Once (YOLO), Mobile Development, iOS, Apple Vision Framework, OpenCV, Core ML, TensorFlow Lite, YOLOv5, Camera API, iOS Camera, Rerun, Image Manipulation, Image Processing, Python, TensorFlow, AI Integration, Object Detection, ONNX Runtime, iOS Video, Video Editing, iOS App Development, OpenAI, Large Language Models (LLMs), Mobile App Development, Video & Audio Processing, Video Processing, Sensor Fusion, Offline-first Development, Software, Sensor Data, Processing & Threading
iOS Developer
2023 - 2024
Fogale Optique SAS
- Designed and implemented a native camera app that allows triggering custom capture events (ISO, focus, resolution, lens type) via C++ and Python.
- Integrated Unity VR app inside native iOS Swift app and custom Interactions with game controllers such as DualShock and Joy-Con.
- Helped integrate and optimize the depth estimation ML model for real-time inference using both TFLite and CoreML.
Technologies: iOS, iOS Camera, Camera API, Video Streaming, Core ML, Streaming, SwiftUI, FastAPI, Algorithms, Machine Learning, Artificial Intelligence (AI), Sockets, Computer Vision, Augmented Reality (AR), Virtual Reality (VR), Mobile Development, ARKit, LiDAR, Apple Vision Framework, App Store, Bluetooth Low Energy (LE), App Store Acceptance Process, Rerun, Metal, Image Manipulation, Image Processing, OpenCV, Python, TensorFlow, AI Integration, Object Detection, TensorFlow Lite, ONNX Runtime, Full-stack, Full-stack Development, PyTorch, WiFi, iOS App Development, Mobile App Development, QR Codes, WebRTC, Audio Streaming, Whisper, Text-to-Speech (TTS), Speech-to-Text (STT), Speech Recognition, Sensor Fusion, Offline-first Development, Software, Sensor Data, Processing & Threading
Senior iOS Developer
2022 - 2022
Articheck
- Fixed memory overflows and reduced app memory to around 80 MB, even with 100+ images uploaded using dedicated URLSessionUploadTask API.
- Sped the upload images fourfold by using four concurrent connections instead of one by one.
- Made images uploaded in the background session instead of always requiring the app to be in the foreground.
- Implemented image upload directly to AWS S3 using pre-signed URLs, reducing upload time twofold and reducing Azure bandwidth cost and CPU time to zero for a particular endpoint.
- Implemented post-upload pre-caching mechanism that fixed app re-downloading just uploaded images without any need, reducing bandwidth again by 50% and local cache size by 50%.
- Reduced the number of HTTP requests from 100+ requests that send annotations metadata to one single request with all metadata overall, making the app more robust and speeding up report upload.
- Refactored the current code to use Adaptable Connectivity APIs and idempotent PUT requests, making the app more robust in case of an HTTP connection failure.
- Implemented debugging tools such as a log viewer and upload viewer and introduced the team to debugging tools such as Charles Web Debugging Proxy and Facebook Flipper for a faster inspection of problems.
- Found and fixed several critical issues related to uploading and did a code review.
- Proposed and gave guidelines for a dozen future improvements, reducing the upload time and bandwidth and improving user experience.
Technologies: iOS, Swift, REST APIs, Background Jobs, GitHub, UIKit, REST, API Integration, APIs, Integration, SwiftUI, Amazon S3 (AWS S3), Amazon Web Services (AWS), Mobile Development, App Store, Back-end, App Store Acceptance Process, RESTFul APIs, Full-stack, Full-stack Development, Authentication, iOS App Development, Cloud Storage, Mobile App Development, Software
Senior iOS Developer
2022 - 2022
Fetch
- Resurrected an acquired app that was not updated for two years.
- Updated dependencies and cleaned the code to conform to the latest iOS platform standard.
- Implemented additional features such as payments and updated the theme to a new modern look.
Technologies: Firebase, Firebase iOS SDK, Swift 5, Swift, iOS, JavaScript, GitHub, UIKit, REST, API Integration, APIs, Integration, SwiftUI, Mobile Development, Back-end, App Store Acceptance Process, RESTFul APIs, Full-stack Development, Node.js, Authentication, iOS App Development, Cloud Storage, Mobile App Development, Software
iOS Developer
2019 - 2020
GameClub (Contract)
- Extended and helped maintain the iOS software development kit (iOS SDK), which included updating theming and implementing the recommendation system.
- Improved and helped maintain the main iOS application used as a game store for the company's game portfolios.
- Assisted in integrating iOS SDK, A/B testing, and numerous analytics across the company's games.
Technologies: iOS, Objective-C, Swift, Xcode, Git, SDKs, UIKit, REST, SDK Development, API Integration, APIs, Integration, Mobile Development, App Store, Back-end, iOS App Development, Mobile App Development, Software
Senior iOS Developer
2018 - 2018
Barclays Investment Bank (Contract)
- Prototyped and rapidly co-developed numerous mobile apps for UK Barclays' research and development team, envisioning future payment solutions.
- Co-developed an iOS queueless restaurant checkout payment concept called Dine & Dash.
- Collaborated on the development of an iOS queueless checkout payment concept named Grab+Go.
Technologies: iOS, Swift, Git, Xcode, RxSwift, Bluetooth GPS, Mobile GPS, Android, Optical Character Recognition (OCR), UIKit, REST, NoSQL, API Integration, APIs, Integration, Core Data, MongoDB, Apple Watch, Algorithms, Near-field Communication (NFC), Embedded Development, Embedded C, Mobile Development, App Store, Back-end, RFID, Push Notifications, Bluetooth Low Energy (LE), Regex, Full-stack, SQL, WiFi, iOS App Development, Mobile App Development, QR Codes, Bluetooth Low Energy (BLE), Audio, Finance, Sensor Fusion, Software, Sensor Data, Processing & Threading
iOS Developer
2017 - 2017
Sonalake (Contract)
- Developed a data gathering and analytical module for iOS for the external client, one of the leading travel companies.
- Implemented unit and functional tests along with tools and fastlane scripts, helping integrate the SDK.
- Implemented secure integration of SDK with back-end server based on JSON Web Tokens (JWT).
Technologies: Core Data, Objective-C, Fastlane, Xcode, JSON, JSON Web Tokens (JWT), XML, Web Services, Fastline, UIKit, REST, API Integration, APIs, Integration, Mobile Development, App Store Acceptance Process, RESTFul APIs, SQL, Authentication, iOS App Development, Mobile App Development, Offline-first Development, Software
iOS Developer
2015 - 2015
Verax Systems (Contract)
- Implemented a mobile profile management system for iOS.
- Provided a critical solution for an iOS background execution and custom certificate installation.
- Coordinated integration with the back-end developer and design improvements with the lead designer.
Technologies: Xcode, Objective-C, iOS, XML, UIKit, REST, API Integration, APIs, Integration, RESTFul APIs, SQL, iOS App Development, Mobile App Development, Software
Co-founder | Lead iOS Developer
2013 - 2014
Square Mountains
- Developed our first flagship iOS application, Peek Calendar.
- Oversaw and helped execute a launch process, resulting in over 50,000 paid app downloads within one month, the app being featured by Apple and many tech blogs, such as The Verge, TechCrunch, Wired, Fast Company, and TNW.
- Co-designed, prototyped, and iterated on numerous mobile app ideations.
Technologies: Git, iOS, Objective-C, Xcode, Slack, UIKit, Mobile Development, App Store, App Store Acceptance Process, iOS App Development, Mobile App Development, Offline-first Development, Software
Junior Java Back-end Developer
2009 - 2010
XTM International
- Implemented and maintained new features for the translation support system.
- Implemented and maintained unit and functional tests in Java.
- Fixed and tracked bug issues in Jira and maintained documentation in Confluence.
Technologies: Java, Java EE (Jakarta EE), Apache Struts, Hibernate, Eclipse, REST, RESTFul APIs, SQL, Software
Junior Java Developer
2008 - 2009
Cognifide
- Co-developed a custom-built content management system (CMS) for numerous clients based on Communique CMS.
- Tracked and fixed bugs using Jira as a reporting tool.
- Built internal tools, scripts, and plugins for Eclipse.
Technologies: Java, Subversion (SVN), Eclipse, Jira, Confluence, Content Management Systems (CMS), MySQL, REST, RESTFul APIs, Software
Experience
Peek Calendar
Peek Calendar is a calendar application for iOS based on Objective-C. I helped co-design it, but I prototyped and fully implemented it. The application got over 50,000 paid downloads within one month and was featured by Apple and many tech blogs.
GameClub
GameClub is an iOS app for exploring companies' game portfolios bundled inside a subscription. It is based on Swift. I helped redesign the main app and implement new features, analytics, A/B testing, etc. Also, I updated and maintained iOS SDK, integrating it across a portfolio of games.
Dine & Dash
Dine & Dash is a research and development project based on Swift. It is an iOS application for queueless checkout payment and split bill concept for restaurant chains. The application is integrated with a custom IoT Totem based on Arduino, using Estimote SDK and Bluetooth low energy beacons for easy pairing and communication along with NFC tags.
Grab+Go
Grab+GO is a Swift-based research and development project. It is an iOS application for queueless checkout payment for supermarket chains. The application uses a smartphone camera to scan barcodes, add products to the shopping cart, and pay instantly.
3D Foot Scanner using iPhone TrueDepth Camera
A mobile application that scans the foot in real-time and creates a 3D mesh model using an iPhone 3D camera and stitched point clouds. Proposed and co-authored a unique algorithm that fuses IMU sensor data with a depth map and color video stream in real-time, providing sub-1 mm accuracy.
Education
2010 - 2011
Student Exchange Program in Interaction Design
Umeå University - Umeå, Sweden
2009 - 2011
Master's Degree in Applications of the Internet of Things
Adam Mickiewicz University - Poznan, Poland
2007 - 2009
Master's Degree in Computer Science
Poznan University of Technology - Poznan, Poland
2004 - 2007
Bachelor's Degree in Computer Science
Poznan University of Technology - Poznan, Poland
Skills
Libraries/APIs
OpenCV, Camera API, REST APIs, Core Image, Apple Subscriptions, NumPy, SciPy, Sockets, RxSwift, Firebase iOS SDK, TensorFlow, AudioKit, React, Core Animation, PyTorch, Node.js, WebRTC
Tools
Xcode, Slack, Git, GitHub, AVPlayer, WebView, You Only Look Once (YOLO), Subversion (SVN), Estimote SDK, Jira, Confluence, Fastlane, Whisper
Languages
Swift, Objective-C, Python, Regex, SQL, Java, C++, C, PHP, HTM, CSS, JavaScript, HTML, Swift 5, XML, Embedded C, Kotlin
Frameworks
SwiftUI, iOS SDK, Core Data, UIKit, Core Bluetooth, Core Location, ARKit, Apple Vision Framework, Apache Struts, Hibernate, JSON Web Tokens (JWT), Metal, Core ML, TensorFlow Lite, React Native
Paradigms
REST, Mobile Development, Offline-first Development
Platforms
iOS, Bluetooth Low Energy (LE), Firebase, Apple Watch, MacOS, WatchOS, Arduino, Eclipse, Java EE (Jakarta EE), Android, Amazon Web Services (AWS)
Storage
JSON, MySQL, MongoDB, NoSQL, Amazon S3 (AWS S3)
Other
Computer Vision, Mobile Apps, App Store, Push Notifications, App Store Acceptance Process, RESTFul APIs, Animation, Authentication, iOS App Development, Mobile App Development, QR Codes, Software, Sensor Data, Bluetooth Beacons, iOS Camera, Bluetooth, SDKs, AVFoundation, Mobile GPS, TrueDepth Camera, Image Manipulation, iOS Video, Machine Learning, API Integration, APIs, Integration, Algorithms, Artificial Intelligence (AI), LiDAR, Object Detection, Back-end, RFID, Audio Streaming, Full-stack, Video Editing, WiFi, OpenAI, Cloud Storage, Bluetooth Low Energy (BLE), Audio, Architecture, Audio Processing, Video & Audio Processing, Video Processing, Sensor Fusion, Processing & Threading, Internet of Things (IoT), Image Processing, Near-field Communication (NFC), Content Management Systems (CMS), Finance, Background Jobs, Subscription Processing, Bluetooth GPS, Web Services, Optical Character Recognition (OCR), Fastline, Point Clouds, Rerun, Computer Vision Algorithms, SDK Development, Augmented Reality (AR), Video Streaming, Streaming, FastAPI, Embedded Development, AI Integration, Virtual Reality (VR), FAISS, YOLOv5, ONNX Runtime, Full-stack Development, Large Language Models (LLMs), Real-time Audio Processing, Text-to-Speech (TTS), Speech-to-Text (STT), Speech Recognition
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