Convert G4 Image Free
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Supported Formats
Convert between all major file formats with high quality
Web Formats
Joint Photographic Experts Group - the most universal image format for photographs using lossy compression. Reduces file sizes 90-95% with minimal visible quality loss. No transparency support. Perfect for photos, web images, email attachments, and any scenario requiring small file sizes. Adjustable quality levels from 1-100. Standard since 1992 with universal device and software support. Ideal for photographs and complex images with many colors.
Portable Network Graphics - lossless image format supporting transparency and 16 million colors. Larger files than JPEG but perfect quality preservation. Supports alpha channel for smooth transparency. Excellent for logos, graphics with text, screenshots, and images requiring transparency. Better compression than GIF for photos. Perfect for web graphics, UI elements, and any image needing lossless quality or transparency. Standard format for web graphics since 1996.
Web Picture format - modern image format by Google providing 25-35% smaller files than JPEG at equivalent quality. Supports both lossy and lossless compression plus transparency. Superior compression algorithms reducing bandwidth usage. Native browser support (96%+ coverage). Perfect for website optimization, web images, and reducing page load times. Combines best features of JPEG, PNG, and GIF. Recommended for modern web development.
Graphics Interchange Format - image format supporting animation and transparency with 256-color limitation. Small file sizes for simple images. Perfect for simple animations, emojis, memes, and graphics with few colors. Lossless for limited palette. Inefficient for photographs (use JPEG) or high-color graphics (use PNG). Universal support since 1987. Standard format for simple web animations and reaction images.
Scalable Vector Graphics - XML-based vector format rendering perfectly at any size. Infinitely scalable without quality loss or pixelation. Small file sizes for geometric shapes and illustrations. Editable with text editors and design software. Perfect for logos, icons, diagrams, and graphics requiring scaling. Supports animation and interactivity. Standard for responsive web graphics and resolution-independent designs. Essential format for modern web icons.
Icon File Format - specialized format for Windows icons containing multiple image sizes (16x16 to 256x256 pixels). Single file provides icons for all display resolutions. Used for favicons, application icons, and Windows shell icons. Supports transparency and multiple color depths. Perfect for website favicons, Windows program icons, and shortcut icons. Standard format for Windows icons since Windows 1.0. Essential for professional Windows applications.
AV1 Image File Format - next-generation image format based on AV1 video codec providing better compression than WebP and JPEG. 20-50% smaller files at equivalent quality. Supports HDR, wide color gamut, and transparency. Cutting-edge compression technology. Growing browser support (85%+ and increasing). Perfect for future-proof web images and maximum efficiency. Better quality at smaller sizes than any previous format. Recommended for modern websites prioritizing performance.
Bitmap Image File - uncompressed raster format from Microsoft providing pixel-perfect quality with large file sizes. No compression means huge files (1MB+ for screenshots). Fast to load and display. Simple format with universal Windows support. Perfect for temporary graphics, screen captures, and scenarios where compression artifacts are unacceptable. Legacy format largely replaced by PNG. Convert to PNG or JPEG for practical use and storage.
Tagged Image File Format - flexible format supporting multiple pages, layers, and various compression methods. Industry standard for professional photography, publishing, and archival. Supports lossless compression, 16-bit color depth, and extensive metadata. Large file sizes but excellent quality. Perfect for print publishing, photo archival, professional photography, and scenarios requiring maximum quality and flexibility. Used in medical imaging and professional scanning.
Professional Formats
Photoshop Document - Adobe Photoshop's native format preserving layers, effects, masks, and all editing capabilities. Supports 16-bit and 32-bit color depths for professional work. Large file sizes due to layer data and editing information. Perfect for ongoing design projects, professional photo editing, and collaborative design work. Not suitable for final output (export to JPEG/PNG). Essential format for professional graphic design and photo manipulation workflows. Industry standard for design files.
OpenEXR - high dynamic range image format developed by Industrial Light & Magic for visual effects and animation. Stores 16-bit or 32-bit floating-point values per channel enabling enormous dynamic range. Supports multiple layers, arbitrary channels, and lossless/lossy compression. Industry standard for VFX, CGI, and professional 3D rendering. Perfect for HDR photography, compositing, and scenarios requiring maximum color precision. Used extensively in film production and high-end visual effects.
High Dynamic Range Image - format storing luminance and color information with greater range than standard images. Captures and displays brightness levels impossible in JPEG/PNG. Uses 32-bit floating-point encoding. Perfect for realistic lighting in 3D rendering, environment maps, and HDR photography. Common in game development and architectural visualization. Enables realistic tone mapping and exposure adjustment. Essential for professional lighting workflows.
DirectDraw Surface - Microsoft texture format for games and 3D applications supporting compressed textures and mipmaps. Optimized for GPU loading with hardware-accelerated decompression. Stores multiple resolution levels (mipmaps) in single file. Standard format for game textures (DirectX, Unity, Unreal). Supports various compression algorithms (DXT1, DXT5, BC7). Perfect for game development, 3D modeling, and real-time rendering. Essential format for game asset pipelines.
Truevision TGA/Targa - raster graphics format supporting 8-32 bits per pixel with alpha channel. Uncompressed or RLE compressed for fast loading. Standard format for video editing, animation, and texture mapping. Excellent color accuracy with optional lossless compression. Perfect for video frame sequences, animation frames, and game textures. Widely supported in 3D software and video editing applications. Reliable format for professional media production.
JPEG 2000 - advanced image format using wavelet compression providing better quality than JPEG at equivalent file sizes. Supports lossless and lossy compression, progressive decoding, and ROI coding. Used in medical imaging, digital cinema, and archival. Better compression artifacts than JPEG. Slower encoding/decoding. Perfect for medical imaging, digital preservation, and applications requiring superior compression. Limited web browser support.
JPEG Stereo - stereoscopic 3D image format storing left and right eye views side-by-side or top-bottom. Based on standard JPEG with special arrangement for 3D viewing. Used for 3D photography, VR content, and stereoscopic displays. Compatible with 3D TVs and VR headsets. Perfect for 3D photography, stereoscopic content creation, and VR/AR applications. Requires special viewing equipment for proper 3D effect.
Portable Float Map - floating-point image format storing HDR color data. Simple format with 32-bit float values per channel. Used in computer graphics for HDR images and height maps. Uncompressed format with large file sizes. Perfect for HDR photography processing, displacement maps, and scientific imaging. Common in 3D rendering and simulation applications. Alternative to OpenEXR for simple HDR storage.
Flexible Image Transport System - scientific image format used primarily in astronomy. Stores astronomical images with extensive metadata headers. Supports multiple data arrays and tables. Standard format for astronomical data archives. Perfect for astronomical imaging, scientific data exchange, and research applications. Used by major observatories and space agencies worldwide. Essential format for astronomical research and data sharing.
How to Convert Files
Upload your files, select output format, and download converted files instantly. Our converter supports batch conversion and maintains high quality.
Frequently Asked Questions
What is a G4 file and why was this format created?
A G4 file is an image encoded using the CCITT Group 4 (G4) fax compression standard. It was created as the successor to Group 3, offering significantly faster and more efficient compression for monochrome scanned documents. Unlike G3-which allowed both 1D and 2D encoding-G4 uses pure 2D compression, referencing patterns between scanlines to dramatically reduce file sizes while maintaining readable text quality.
G4 became the standard for high-speed digital faxing, enterprise document scanning, and archival systems that needed compact but high-accuracy black-and-white reproductions. Today, it remains crucial inside TIFF-G4 files used by scanners and enterprise imaging systems.
How is a G4 file structured internally?
G4 files use a rigid and highly optimized structure built for speed and compression:
1-bit Monochrome Format
Each pixel is strictly black or white. This restriction enables high compression and predictable structure.
Pure 2D Modified READ Encoding
G4 always uses 2D line-by-line encoding, referencing differences between lines to reduce repeated patterns.
No End-of-Line Markers
Unlike G3, G4 does not insert EOL markers because the 2D structure eliminates the need, further reducing size.
Fixed Telefax Resolutions
Common scan widths include 1728, 2048, and 2432 pixels per line, matching historical fax resolutions.
This structure makes G4 extremely efficient and more robust than G3 when compressing text documents.
Where are G4 files used today?
G4 encoding is still heavily used in modern enterprise systems:
TIFF G4 Document Scanners
Most office scanners export monochrome scans using Group 4 compression inside TIFF containers.
Enterprise Archival Systems
Banks, courts, and medical institutions archive decades of documents in TIFF-G4 format.
Telecommunications Backends
Digital fax servers often convert incoming pages into G4 for storage efficiency.
Government and Law Enforcement Repositories
Regulated industries trust G4 for long-term preservation of forms and scanned records.
OCR Pipelines
OCR systems frequently ingest G4-based TIFFs due to their sharp monochrome text output.
Legal and Compliance Workflows
Many courts only accept scanned documents in TIFF-G4 format for consistency.
Low-Bandwidth Transmission Systems
Although less common, G4 is still used in specialized communication systems with bandwidth limits.
Even with modern imaging formats available, G4 remains widely used because of its reliability and tiny file size.
Why do some G4 images appear extremely sharp but low-depth?
G4 is restricted to 1-bit monochrome, so all subtle shades or grayscale information is lost.
This sharpness is intentional-G4 was optimized for crisp text, not photographic detail.
Documents that rely on shading, stamps, or gradients may appear rough or heavily dithered.
How does G4 compare to G3, TIFF G4, and PDF?
Compared to G3, G4 is significantly more compressed, faster to decode, and more consistent because it always uses 2D encoding.
TIFF G4 is essentially G4 data stored inside a TIFF wrapper with page structure and metadata support.
PDF can embed G4 images directly but adds text layers, metadata, fonts, and structure unavailable in standalone G4 streams.
Does the G4 format support grayscale, color, or transparency?
No-G4 supports only black and white pixels.
There is no alpha channel support, and no grayscale or RGB information can be stored.
Any grayscale input must be thresholded or dithered before encoding.
Why do some programs refuse to open G4 files?
Many applications expect G4 compression to be wrapped inside TIFF instead of a raw .g4 stream.
Some G4 files omit dimensional metadata, requiring manual width/height input for decoding.
Not all viewers support pure CCITT Group 4 decoding, especially lightweight or web-based viewers.
Why do G4 conversions sometimes fail?
Conversion failures usually stem from fax-era constraints:
Dimension Ambiguity
Raw G4 files often lack intrinsic width/height, forcing conversion tools to guess or require manual input.
Strict Binary Requirements
G4 can only accept pure black-and-white images; color or grayscale must be converted first.
Non-Standard Line Encodings
Some telecom vendors introduced proprietary variations incompatible with generic decoders.
Odd Line Widths
Older fax systems sometimes used unusual resolutions that modern tools do not expect.
Headerless Bitstreams
Many .g4 files are raw encoded streams containing no metadata, making automated conversion difficult.
Tools like ImageMagick, Ghostscript, and fax utilities handle G4 better than generic image editors.
Does G4 support metadata or multi-bit depth?
No-raw G4 streams include no metadata of any kind.
TIFF-G4 adds metadata layers, but the compression itself does not store additional fields.
G4 cannot encode grayscale, DPI info, timestamps, or color spaces internally.
What modern uses does G4 still have?
G4 continues to play a major role in several fields:
Large-Scale Document Archiving
Mass digitization projects use TIFF-G4 to store millions of scanned pages compactly.
Court and Legal System Requirements
Many jurisdictions mandate TIFF-G4 for evidence submissions and scanned legal filings.
OCR and Machine Learning
OCR systems rely on sharp black-and-white G4 images for improved text extraction performance.
Telecom Fax Gateways
Digital fax servers commonly convert pages to G4 for compact storage.
Unix Imaging Tools
ImageMagick, NetPBM, and Ghostscript have strong support for G4 for document processing.
Low-Overhead Archival Workflows
G4’s tiny file sizes reduce storage costs for massive corporate archives.
Corporate and Medical Records
Hospitals and insurance companies still use TIFF-G4 for high-speed scanning workflows.
Forensic Document Analysis
Investigators analyze noise patterns and encoding behavior in original G4 scans.
Fax Replay Systems
Developers use G4 streams to test and simulate fax transmission behaviors.
Long-Term Digital Preservation
Because of its simplicity and guaranteed readability, G4 remains a preservation-friendly format.
Why are G4 files so small?
G4 uses highly efficient 2D compression that eliminates redundant patterns between scanlines.
Only 1-bit data is stored, drastically reducing storage requirements.
There are no color channels, metadata, or container structures added.
How large can a G4 file get?
Most G4 pages remain under 30–50 KB, even for full A4 or letter-sized documents.
Dense text or complex diagrams produce slightly larger files but remain compact compared to modern scans.
Only multi-page TIFF-G4 archives become large due to page count rather than compression inefficiency.
Does G4 support multi-page documents?
No-raw G4 files contain exactly one page.
Multi-page storage is achieved by wrapping multiple G4 streams inside TIFF.
Fax systems transmitted pages individually but compiled them externally.
Why do some G4 images appear warped or stretched?
G4 relies on fax-era non-square pixel resolutions; incorrect DPI handling can distort images.
Some viewers default to square pixels, misrepresenting the intended fax geometry.
Headerless streams require manual DPI and width/height entry to display correctly.
Is the G4 format still relevant today?
Yes-G4 remains the dominant compression used in enterprise scanners and legal document archives.
Its incredibly small size and predictable structure make it ideal for long-term document preservation.
While not suitable for photos or color images, G4 continues thriving in medical, legal, telecom, and archival workflows.
About the G4 Format
G4 is a file format used in specific workflows. The exact characteristics depend on the implementation and chosen settings.
- Format Type
- File format
- Origin
- Industry-developed format
- Common Uses
- Various applications that support G4
- Compression
- Depends on implementation
Sources and References
Format details on this page are based on the official specifications and documentation below.
- Image file type and format guide- MDN Web Docs