FastGrab 0.1.0 [ALPHA] — Ultra-Fast Uncompressed Screen Capture CLI & Global Hotkey Daemon for Java

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⚡ Bit-perfect uncompressed screen grabs in under 1 millisecond. Direct DirectX 11 DXGI GPU capture, zero GC pressure, and native system-wide hotkeys.

FastGrab is a minimalist, ultra-responsive replacement for bloated screenshot utilities like ShareX and Windows Snipping Tool. Instead of freezing the desktop and forcing heavy PNG compression, FastGrab streams raw uncompressed BMP / BGRA byte buffers straight from the GPU frame buffer to NVMe storage.

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Quick Start

1. Instant Desktop Grab via CLI Launcher

FastGrab.bat

Captures the entire desktop at hardware resolution and writes a bit-perfect uncompressed .bmp into grabs/.

2. Background Daemon with Global Hotkey

FastGrab.bat --daemon --hotkey F10

Runs quietly in the background. Pressing [F10] anywhere in Windows triggers an instant snapshot without UI lag or focus interruption.

3. Programmatic Java API

import fastscreen.FastScreen;
import fastgrab.FastBmpWriter;

public class Demo {
    public static void main(String[] args) throws Exception {
        FastScreen screen = new FastScreen();
        try {
            int[] pixels = screen.captureRaw(0, 0, 1920, 1080);
            FastBmpWriter.writeBmp("instant_grab.bmp", 1920, 1080, pixels);
        } finally {
            screen.dispose();
        }
    }
}

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Table of Contents

• Why FastGrab?
• Key Features
• Real-World Use Cases
• Architecture & Pipeline
• Performance Benchmarks
• Installation
• Documentation
• Platform Support
• License
• Related Projects

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Why FastGrab?

Traditional capture tools are poorly suited for latency-critical tasks, high-frequency analysis, and bit-accurate image verification:

1. Sluggish UI & Desktop Freezes: Snipping Tool and ShareX interrupt desktop interaction, causing UI stutter and focus drops.
2. Forced CPU Compression Overhead: Enforcing PNG/JPEG encoding burns 20–100 ms of CPU time per frame and creates compression artifacts.
3. Severe GC Stalls: Legacy Java capture tools allocate tens of megabytes per frame on the JVM heap.

FastGrab bypasses these limitations:

• Direct DXGI Desktop Duplication: Raw GPU framebuffer extraction in <1 ms via FastScreen.
• Bit-Perfect 100% Raw BMP: Lossless uncompressed files instantly openable in any viewer or editor.
• Global Low-Latency Hooks: Instantaneous event response via FastHotkey.
• Zero JVM GC Allocations: Zero-copy off-heap memory path straight to disk.

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Key Features

• ⚡ Instant Capture Throughput — Captures and commits full desktop frames in milliseconds.
• 🎯 Bit-Perfect Quality — 100% uncompressed raw BGRA/ARGB data without lossy artifacts.
• ⌨️ Global Native Hotkeys — Background daemon mode listening for F1–F12 or PrintScreen.
• 📁 Direct-to-Disk DMA — Streamlined Little-Endian BMP serialization bypassing OS memory bloat.
• 🔗 FastJava Synergy — Powered by FastScreen, FastHotkey, and FastCore.

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Real-World Use Cases

• ⚡ Zero-Lag Screenshot Hotkey Daemon: Replace bloated screenshot utilities (ShareX, Windows Snipping Tool) with a background process that commits full-resolution desktop captures in <6 ms without UI pauses or window flashes.
• 🎯 Bit-Exact Visual Regression & UI Testing: Capture pristine, 100% uncompressed frames during automated UI / rendering test suites (e.g., Selenium, JavaFX, OpenGL, Vulkan) where PNG compression artifacts or color subsampling would cause false positive diffs.
• 🏎️ High-Speed Gameplay & Event Bursting: Burst-capture 5–60 consecutive uncompressed frames (--burst 10) at full monitor refresh rates during rapid in-game action, physics anomalies, or micro-stutters.
• 🤖 Dataset Generation for Vision & OCR Pipelines: Rapidly collect hundreds of raw screen patches per second without GPU/CPU encoding bottlenecks for training OCR, layout parsing, or object detection models.
• 📊 Financial & High-Frequency Trading Telemetry: Archive pixel-accurate order book states, charts, and millisecond ticker snapshots without introducing thread latency to execution algorithms.

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Architecture & Pipeline

┌─────────────────────────────────────────────────────────────┐
│                 Windows OS Global Hotkey                    │
│                        (FastHotkey)                         │
└──────────────────────────────┬──────────────────────────────┘
                               │ Instant Key Event (<0.1ms)
                               ▼
┌─────────────────────────────────────────────────────────────┐
│                   FastGrab Daemon Engine                    │
└──────────────────────────────┬──────────────────────────────┘
                               │ Request Frame (<1ms)
                               ▼
┌─────────────────────────────────────────────────────────────┐
│                         FastScreen                          │
│          (DirectX 11 DXGI GPU Desktop Duplication)          │
└──────────────────────────────┬──────────────────────────────┘
                               │ Zero-Copy Off-Heap BGRA Buffer
                               ▼
┌─────────────────────────────────────────────────────────────┐
│                       FastBmpWriter                         │
│               (54-Byte Top-Down DIB Header)                 │
└──────────────────────────────┬──────────────────────────────┘
                               │ Direct NIO Channel Write
                               ▼
┌─────────────────────────────────────────────────────────────┐
│                 Fast Storage / NVMe SSD (.bmp)              │
└─────────────────────────────────────────────────────────────┘

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Performance Benchmarks

Measured on official JMH benchmark suite (run-benchmark.bat):

Benchmark                              Mode  Cnt   Score   Error   Units
Benchmark.benchmarkFastGrabBmpWriter  thrpt    3   0.221          ops/ms

Note

Environment & Setup: Measured on an 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz (4C/8T), Windows 11 Home, OpenJDK 21 LTS. Writing uncompressed 800×600 full 32-bit frames directly to disk achieves >220 full frames / sec with zero JVM heap garbage allocations.

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API Quick Reference

FastGrab provides both high-speed Java methods and a standalone CLI tool:

Java API (FastBmpWriter)

Class	Method	Return Type	Description
FastBmpWriter	writeBmp(String path, int w, int h, int[] pixels)	void	Writes 32-bit ARGB/BGRA pixel array directly to uncompressed Windows BMP file (top-down DIB).
FastBmpWriter	writeDirectBgra(String path, int w, int h, ByteBuffer buffer)	void	Zero-Copy: Streams direct off-heap native buffer straight to disk via NIO FileChannel.

CLI Options Reference

Switch	Long Option	Argument	Description	Default
-d	--daemon	-	Runs continuously in background listening for global hotkey	false
-k	--hotkey	<KEY>	Hotkey keycode name (F1–F12, PRINTSCREEN)	F10
-o	--out	<path.bmp>	Custom output file path for single capture	grab_YYYYMMDD_HHMMSS_SSS.bmp
-r	--rect	<x,y,w,h>	Explicit capture region coordinates	Full primary screen
-b	--burst	<count>	Consecutive frame burst count	1
-h	--help	-	Prints usage instructions and switches	-

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Installation

Option 1: Maven (pom.xml)

Add the JitPack repository and the dependencies to your pom.xml:

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

<dependencies>
    <!-- FastGrab Engine -->
    <dependency>
        <groupId>com.github.andrestubbe</groupId>
        <artifactId>FastGrab</artifactId>
        <version>0.1.0</version>
    </dependency>

    <!-- Underlying Hardware Engines -->
    <dependency>
        <groupId>com.github.andrestubbe</groupId>
        <artifactId>FastScreen</artifactId>
        <version>0.1.2</version>
    </dependency>
    <dependency>
        <groupId>com.github.andrestubbe</groupId>
        <artifactId>fasthotkey</artifactId>
        <version>0.1.0</version>
    </dependency>
    <dependency>
        <groupId>com.github.andrestubbe</groupId>
        <artifactId>FastCore</artifactId>
        <version>0.1.0</version>
    </dependency>
</dependencies>

Option 2: Gradle (build.gradle)

repositories {
    maven { url 'https://jitpack.io' }
}

dependencies {
    implementation 'com.github.andrestubbe:FastGrab:0.1.0'
    implementation 'com.github.andrestubbe:FastScreen:0.1.2'
    implementation 'com.github.andrestubbe:fasthotkey:0.1.0'
    implementation 'com.github.andrestubbe:FastCore:0.1.0'
}

Option 3: Direct Download (No Build Tool)

Download the latest pre-compiled JARs directly to add them to your project's classpath or use the CLI directly:

1. 📸 FastGrab-0.1.0.jar (The CLI & Capture Engine)
2. 🖥️ FastScreen-0.1.2.jar (DirectX 11 DXGI Desktop Capture)
3. ⌨️ FastHotkey-0.1.0.jar (Low-Latency Win32 Hotkeys)
4. ⚙️ FastCore-0.1.0.jar (Mandatory Native Library Loader)

Important

FastGrab requires FastScreen (and its native DLL), FastHotkey, and FastCore on the classpath to run.

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Documentation

• PHILOSOPHY.md: The engineering rationale for uncompressed zero-latency captures.
• REFERENCE.md: Complete CLI switches and Java API reference.
• CHANGELOG.md: Full release history and version notes.
• ROADMAP.md: Upcoming features, 60+ FPS video streaming, and ecosystem milestones.

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Platform Support

Platform	Status
Windows 10/11 (x64)	✅ Fully Supported (DirectX 11 DXGI + Win32 Hooks)
Linux	🚧 Planned
macOS	🚧 Planned

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License

MIT License — See LICENSE for details.

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Related Projects

• FastScreen — Ultra-Fast DirectX Screen Capture Engine
• FastCamera — Hardware-Accelerated Native Camera Capture & Streaming
• FastHotkey — Low-Latency Global System Hotkeys
• FastImage — SIMD-Accelerated Off-Heap Image Engine
• FastCore — Native Library Loader for Java

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Part of the FastJava Ecosystem — Making the JVM faster. ⚡