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Multiple-image Network Graphics
Multiple-image Network Graphics
Multiple-image Network Graphics
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Multiple-image Network Graphics
Filename extension
.mng
Internet media type
video/x-mng (unofficial)
Developed byPNG Development Group (donated to W3C)
Type of formatcomputer animation
Container forPNG, JNG
Extended fromPNG

Multiple-image Network Graphics (MNG) is a graphics file format published in 2001 for animated images. Its specification is publicly documented and there are free software reference implementations available.

MNG is closely related to the PNG image format. When PNG development started in early 1995, developers decided not to incorporate support for animation, because the majority of the PNG developers felt that overloading a single file type with both still and animation features is a bad design, both for users (who have no simple way of determining to which class a given image file belongs) and for web servers (which should use a MIME type starting with image/ for stills and video/ for animations—GIF notwithstanding),[1] but work soon started on MNG as an animation-supporting version of PNG. Version 1.0 of the MNG specification was released on 31 January 2001.

File support

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Support

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Gwenview has native MNG support. GIMP can export images as MNG files. Imagemagick can create a MNG file from a series of PNG files. With the MNG plugin, Irfanview can read a MNG file.[2] If MPlayer is linked against libmng, it and all its graphical front-ends like Gnome MPlayer can display MNG files.

Mozilla browsers and Netscape 6.0, 6.01 and 7.0 included native support for MNG until the code was removed in 2003 due to code size and little actual usage,[3] causing complaints on the Mozilla development site.[4] Mozilla later added support for APNG as a simpler alternative.[5] Similarly, early versions of the Konqueror browser included MNG support but it was later dropped. MNG support was never included in Google Chrome, Internet Explorer, Opera, or Safari.

Product Support status
Image processing
Chasys Draw IES Yes
GIMP Partial
Gwenview Yes
ImageMagick Yes
Irfanview Partial, via plugin
KMPlayer Yes
Konvertor Yes
MPlayer Yes
XnView Yes

Server support

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Web servers are generally not pre-configured to support MNG files.[6][7]

The MNG developers had hoped that MNG would replace GIF for animated images on the World Wide Web, just as PNG had done for still images.[8] However, with the expiration of LZW patents and existence of other alternative file formats such as APNG, Flash, and SVG, web usage of MNG was far less than its developers had expected.

Technical details

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The structure of MNG files is essentially the same as that of PNG files, differing only in the slightly different signature (8A 4D 4E 47 0D 0A 1A 0A in hexadecimal, where 4D 4E 47 is ASCII for "MNG" – see Portable Network Graphics: File header) and the use of a much greater variety of chunks to support all the animation features that it provides. Images to be used in the animation are stored in the MNG file as encapsulated PNG or JNG images.

To allow applications to include some level of MNG support without having to implement the entire MNG specification, two reduced-complexity versions of MNG are also defined: MNG-LC (low complexity) and MNG-VLC (very low complexity). These reduced specifications are conceptually similar to the "SVG Basic" and "SVG Tiny" subsets offered in the SVG standard.

MNG does not have a registered MIME media type, but video/x-mng or image/x-mng can be used. MNG animations may be included in HTML pages using the <embed> or <object> tag.

Saving a file as MNG can be either lossy or lossless, depending on whether its frames are encoded in PNG (lossless) or JNG (lossy).

Alternatives

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Most modern web browsers support animations in APNG, SVG, WebP, and WebM. As of February 2024 only Apple Safari supports HEIF and JPEG XL.[9] Internet Explorer only supported GIF, CSS, and Flash animations.

The most common alternatives to MNG have been Animated GIF and – until it was deprecated in 2017[10] – Adobe Flash. GIF images are restricted to 256 colors with limited compression, but the format is supported in all graphical web browsers and is still widely used.

Animations can also be generated ad hoc in a browser with the CSS 3 features animations, transitions, and sprites, or with the web animations API of JavaScript, by specifying frames or motions of still images or rendered shapes. Ad-hoc animations can be resource-intensive, and they generally cannot be saved in a portable file or posted on imageboards.

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Multiple-image Network Graphics

View on Grokipedia
from Grokipedia
Multiple-image Network Graphics (MNG) is a public-domain graphics file format in the family, designed to support animations, slide shows, and complex still frames through sequences of embedded or Network Graphics (JNG) images, while enabling efficient data reuse and incremental updates via . Developed as an extension to to address its limitations for multi-image content, MNG originated from discussions within the PNG development community in the mid-1990s, with serious design work beginning in May 1996 and the format emerging on the in August 1998. The specification reached version 1.0 on January 31, 2001, after nearly four years of evolution led primarily by Glenn Randers-Pehrson, incorporating feedback to balance complexity with usability. Its creation was motivated by the need for a patent-free alternative to animated for web-based animations, leveraging lossless compression, alpha transparency, and while adding support for progressive loading and object manipulation. MNG files use a chunk-based structure similar to , starting with an 8-byte signature and an MHDR chunk that defines parameters like frame dimensions, rate for timing, and complexity profile, followed by image data streams and control chunks such as FRAM for frame boundaries, LOOP for repetitions, and SHOW for visibility management. Key features include Delta-PNG for encoding differences between frames to reduce , support for layered compositions and partial updates, integration of lossy JNG for efficient handling with transparency, and subsets like MNG-LC (low complexity) and MNG-VLC (very low complexity) for simpler implementations. The format's type is video/x-mng, with files typically using the .mng extension, and it excludes audio or video, recommending MPEG for such needs. Although early applications like and provided support by 1999, MNG adoption has remained limited, with major web browsers such as (post-2003), Chrome, Internet Explorer, Opera, and Safari dropping or never implementing native playback due to complexity and competition from simpler formats like . As of 2025, MNG sees niche use in specialized software for animation creation and viewing, such as through the libmng reference library.

History and Development

Origins and Motivation

The development of Multiple-image Network Graphics (MNG) began in 1995 as an initiative by the PNG Development Group to extend the format with support for animations and multiple images, without modifying the core PNG specification. This effort was motivated by the need for a patent-free alternative to the , which relied on the patented Lempel-Ziv-Welch (LZW) compression algorithm and offered limited features such as only 256 colors per frame and basic transparency. By building on PNG's established lossless compression and alpha channel transparency, MNG aimed to provide superior web-compatible animation capabilities for graphics designers and developers seeking high-quality, royalty-free options. Early discussions on the topic emerged alongside PNG's own creation, with initial ideas for multi-image extensions surfacing in the mid-1990s on the comp.graphics Usenet newsgroup, where PNG had been conceived as a GIF replacement. However, following the intense work on PNG's specification, which was finalized in 1996, the PNG group experienced fatigue, delaying serious MNG design until May 1996. The primary motivation was to enable lossless animations, slideshows, and progressive image sequences for the web, capitalizing on PNG's growing adoption as a versatile single-image format while addressing GIF's shortcomings in color depth and compression efficiency. Glenn Randers-Pehrson served as the primary author and editor of MNG, authoring nearly all drafts starting in and shaping its modular structure to mirror 's extensibility through chunk-based design. Contributions from other group members, including Thomas Boutell and Greg Roelofs, focused on ensuring with datastreams and support for emerging needs like combining with JPEG Network Graphics (JNG) for mixed lossless and lossy content. The initial goals emphasized creating a dedicated format for dynamic web graphics that maintained 's patent-free status, high fidelity, and openness, positioning MNG as a natural evolution for multimedia applications without the legal encumbrances of .

Standardization Process

The development of Multiple-image Network Graphics (MNG) originated in 1996, when discussions within the community identified the need for an extension supporting multiple images, animations, and related features, leading to initial design efforts hosted by libpng.org. This site served as the central repository for the project, fostering collaboration among developers and providing public access to drafts and resources. Over the subsequent years, the format evolved through iterative refinements, balancing comprehensive capabilities with practical implementation concerns. By early 2001, the MNG specification achieved version 1.0 status on January 11, following approval via a formal vote by the PNG Development Group, with the final edited document published on January 31. This milestone marked the completion of the core standardization process, establishing MNG as a modular extension of the PNG family capable of embedding PNG and JNG datastreams for animations and complex compositions. The specification was released under open terms, free of patents or licensing fees, enabling unrestricted adoption similar to PNG itself. In response to feedback on the format's perceived complexity, the version 1.0 specification incorporated simplified subsets, including MNG-LC (Low Complexity) for reduced feature sets and MNG-VLC (Very Low Complexity) as a minimal profile suitable for basic animations. These variants aimed to lower barriers to implementation while maintaining backward compatibility with the full format. However, due to limited industry uptake compared to alternatives, MNG did not progress to formal recommendation status by standards bodies like the W3C, and no substantive revisions to the core specification have been made since 2003.

Format Fundamentals

Core Components

Multiple-image Network Graphics (MNG) files utilize the .mng file extension, with lowercase preferred for compatibility across case-sensitive systems. The unofficial type assigned to MNG is video/x-mng, serving as an interim designation until formal registration of video/mng could be pursued. MNG is optimized for multi-image applications, supporting animations, slideshows, and complex still frames composed of multiple sub-images, while also accommodating single-image storage for basic use cases. Although capable of containing a standalone , the format's design emphasizes efficiency in handling sequences of images, such as through data reuse across frames to minimize redundancy without requiring retransmission. Compression in MNG leverages lossless methods via PNG sub-images, including Delta-PNG techniques that encode differences from a image to reduce , and lossy options through JNG for photographic content. This dual approach allows MNG to balance quality and efficiency, with JNG specifically combining compression for color data alongside for optional alpha transparency. Developed with web deployment in mind, MNG files are embeddable in documents using or tags, facilitating progressive display and integration into dynamic web pages similar to its foundation for lossless elements.

Integration with PNG and JNG

Multiple-image Network Graphics (MNG) integrates seamlessly with the format by embedding complete PNG datastreams—consisting of IHDR, IDAT, and IEND chunks without the PNG signature—for representing lossless image frames within an animation sequence. This allows MNG to leverage PNG's established and transparency capabilities directly, enabling the reuse of PNG objects via mechanisms like the DEFI chunk to define their placement and properties across frames. To support for photographic content while maintaining alpha channels, MNG incorporates JPEG Network Graphics (JNG), a format developed specifically as a sub-format of MNG to encapsulate baseline or progressive JPEG datastreams (via JDAT chunks) alongside optional lossless alpha representations (via IDAT or JDAA chunks), all bounded by JHDR and IEND chunks. JNG was introduced alongside MNG around to facilitate progressive loading and efficient transparency in animated sequences, allowing decoders to handle 8-bit JPEGs mandatorily and 12-bit optionally. This integration shares PNG's chunk structure—length, name, data, and CRC—ensuring structural , where JNG files can also stand alone with their distinct signature (139 74 78 71 13 10 26 10). For , MNG files begin with a unique (138 77 78 71 13 10 26 10) and use the .mng extension, but they can contain a single embedded or JNG datastream, permitting unsupported viewers to fallback to displaying just the first lossless frame as a static image. The MHDR chunk's bit flags further indicate supported features, such as the presence of JNG, allowing simplified profiles like MNG-VLC (very low complexity, no JNG) for broader . By combining for precise lossless elements and JNG for compact lossy ones—often with Delta-PNG for encoding frame differences—MNG achieves significant file size reductions; for instance, delta frames with mostly zeros can compress to under 1% of a full equivalent, lowering bandwidth needs for complex animations compared to pure sequences.

Technical Specifications

File Structure and Chunks

Multiple-image Network Graphics (MNG) files employ a chunk-based structure inspired by the format, enabling modular organization of data for animations and multiple images. The file begins with an 8-byte signature similar to PNG's but differing in the first byte (\x8AMNG\r\n\x1A\n), followed immediately by the mandatory MHDR chunk, which defines essential parameters such as the overall width and height of the animation canvas in pixels, the tick duration for timing (ticks per second, where if set to 0 it is treated as 1000 for 1 ms ticks), the number of frames and layers, and a simplicity profile byte indicating supported features. Intermediate chunks handle image data, object definitions, and control instructions, culminating in the mandatory MEND chunk (zero-length), which signals the end of the datastream and ensures integrity. Key chunk types facilitate efficient handling of repeated elements and composition. The SAVE chunk marks a checkpoint to freeze the current state of objects (such as images or layers) for later reuse, allowing decoders to store and restore them without reprocessing. Paired with SAVE, the SEEK chunk enables navigation to saved points, optionally including a segment name for identification, which optimizes streaming by discarding intermediate data. For compositing, the CLIP chunk specifies clipping boundaries (left, right, top, bottom offsets in pixels) for objects, either replacing or modifying prior definitions to define visible regions. The PASTE chunk supports advanced layering by pasting a source image or object into a destination object at specified coordinates, with options for boundary and delta encoding to minimize redundancy. Additionally, the BACK chunk establishes the background, providing an optional or mandatory solid color (in sRGB or linear space) or a referenced image object, which underlies all frames unless overridden. MNG's extensibility mirrors PNG's design, with each chunk prefixed by a 4-byte length field (big-endian), followed by a 4-byte type code (ASCII letters), variable-length data, and a 4-byte (CRC-32) for error detection. This allows ancillary chunks (non-critical) for private extensions, registered through official channels, while critical chunks must be processed by compliant decoders to avoid errors. Variants of MNG adjust chunk usage for reduced complexity. The full MNG format supports all chunks, including those for and like SAVE, SEEK, CLIP, and PASTE. In contrast, MNG-LC (Low Complexity), defined by a simplicity profile with bit 0 set and others mostly cleared in the MHDR, omits advanced features and stored object buffers, relying instead on straightforward frame sequences without PASTE or complex clipping to simplify decoding for resource-constrained environments.

Animation and Playback Control

Multiple-image Network Graphics (MNG) manages frame sequencing through the FRAM chunk, which defines boundaries between subframes, specifies interframe delays in ticks, and controls disposal methods such as replacing or overlaying previous content to create smooth transitions. The FRAM chunk supports four framing modes that determine how backgrounds and foregrounds are generated and timed, enabling variable frame rates by allowing delays to vary per layer or subframe while ensuring minimum display times for each frame. Timing in MNG animations is established by the MHDR chunk, which sets the ticks_per_second parameter to define the unit for all delays—typically 1000 ticks per second (1 tick = 1 ms), though it can be 0 (treated as 1000) or adjusted up to 4294967295 for precise control—and supports looping via the LOOP chunk that specifies iteration counts up to 2^31-1, with nesting for complex sequences. The LOOP chunk allows animations to repeat indefinitely (iteration count of 0) or a finite number of times, facilitating playback in forward or backward directions through combined use with SHOW chunk modes that cycle through images. Compositing in MNG relies on the PASTE chunk for layering images over existing frames using alpha blending to handle transparency effects, where modes like "over" or "replace" integrate new content with disposal to clear or retain prior layers. The SHOW chunk complements this by controlling visibility and rendering of stored images, generating layers for display while supporting pausing through zero-delay ticks or external signals. In the MNG-VLC variant, playback is simplified to basic show/hide operations without advanced , limiting features to single-layer frames and excluding variable positioning or alpha blending for reduced complexity.

Implementation and Support

Software Compatibility

Multiple-image Network Graphics (MNG) files can be created, edited, and viewed using a variety of desktop software tools, though support remains niche compared to more common formats like or . Image editors such as provide native export capabilities for MNG, allowing users to save animations directly from layered projects, while import functionality relies on external plugins that may require updates for full compatibility. , a popular editor, lacks native MNG import and export in its core features as of 2025, with community discussions highlighting limited workarounds through third-party scripts or conversions rather than built-in tools. For viewing and library-based processing, offers full read and write support for MNG, enabling command-line operations like conversion, resizing, and animation playback in scripts or applications. Similarly, , a of , provides comprehensive read/write capabilities for MNG files, maintaining compatibility with the format's animation and transparency features. The libmng library serves as the for MNG, supporting decoding, encoding, and manipulation; while its last major update occurred in 2011, it remains stable and is integrated into various tools without significant changes through 2025. In scientific imaging contexts, Bio-Formats includes robust MNG reader support, rated as good for metadata extraction and handling, with updated as recently as August 2025. Media players like can handle MNG playback when compiled with libmng integration, rendering animations smoothly in a video-like interface. offers potential MNG support through libmng dependencies, though it is not a primary format and may require specific builds for reliable animation rendering. On systems, and Gwenview provide native viewing for MNG files, with Gwenview capable of displaying animated sequences and basic editing like rotation. Creation tools for MNG are often web-based or converter-focused, as native options are scarce. Online services like Ezgif remain active in 2025, offering free tools to assemble MNG files from image sequences, convert between MNG and other formats, and optimize animations without watermarks or limits. Notably, neither macOS Preview nor Windows Photos app includes native preview or support for MNG files as of 2025, necessitating third-party software for handling them on these platforms. Historical browser support for MNG has largely declined since the early 2000s, shifting focus to desktop tools for practical use.

Browser and Server Support

Multiple-image Network Graphics (MNG) has limited browser support, primarily historical and confined to early implementations. and early versions provided native support for MNG until June 2003, when it was removed due to the format's large decoder size (approximately 287 KB on ), poor integration, lack of active maintainers, and negligible real-world adoption compared to alternatives like animated GIFs and Flash. As of 2025, no major web browsers offer native MNG support: , , Apple Safari, and modern versions do not render MNG files without external aids, reflecting the format's decline since the early . Partial support was available in older versions (4.0 and higher) through plugins like MNG4IE, an control that enabled rendering but required low security settings. On the server side, deploying MNG files requires manual configuration, as the format is not enabled by default in common web servers or content delivery networks (CDNs). The official type for MNG is video/x-mng, which must be explicitly added to via .htaccess files or httpd.conf (e.g., AddType video/x-mng .mng) and to in the mime.types file (e.g., video/x-mng mng;). Major CDNs like and Akamai do not include video/x-mng in their default MIME mappings, often treating MNG as an unknown type and advising fallbacks to static for compatibility. Workarounds for MNG's lack of native web support include JavaScript-based polyfills that emulate playback by decoding frames client-side, though these are rudimentary and not widely maintained, or converting MNG files to more supported formats like or using tools such as . The 2025 update to the specification (Third Edition) officially incorporates for animations via new chunks like acTL and fcTL, enhancing its web viability while making no provisions for MNG integration. MNG's web adoption remains negligible as of 2024-2025 analyses, comprising less than 0.1% of animated images online, overshadowed by (16.3% of all images) and emerging formats like and . This low usage stems from early browser abandonment and the rise of simpler alternatives, confining MNG to niche or archival applications rather than broad web deployment.

Advantages, Limitations, and Alternatives

Key Benefits and Drawbacks

Multiple-image Network Graphics (MNG) offers several advantages over the format, particularly in handling transparency and compression for animated content. Unlike , which is limited to 1-bit transparency, MNG supports full 8-bit alpha channels for smooth, variable transparency in animations, enabling more sophisticated without color limitations or restrictions associated with GIF's LZW compression. Additionally, MNG employs lossless compression inherited from , preserving image quality across frames while allowing for progressive loading, where partial animations can display incrementally as data arrives, improving perceived performance on slower networks. MNG's integration with JPEG Network Graphics (JNG) further enhances efficiency by combining lossy compression for color data with lossless PNG alpha channels, resulting in smaller file sizes for complex images compared to fully lossless alternatives. This hybrid approach supports advanced operations, such as layering multiple images with precise blending modes, making MNG suitable for intricate animations that require both efficiency and visual fidelity. Despite these strengths, MNG's primary drawback is its high structural complexity, stemming from extensive chunk-based features for animation control and , which complicated implementation and led to the development of simplified subsets like MNG-LC (low complexity) and MNG-VLC (very low complexity) to reduce decoder overhead. Development of the format has been stagnant since its 2001 specification, with no significant updates or community momentum after around 2003, when major projects like discontinued support due to integration challenges. This lack of evolution has left MNG without modern features, such as (HDR) integration, which PNG received in its 2025 specification update. File sizes for MNG animations with transparency are often substantially smaller than equivalent GIFs—sometimes a fraction of the size—due to superior compression, but they tend to be larger than those achieved with optimized animations, which benefit from more advanced algorithms. Poor ecosystem support, including limited browser and software adoption, has overshadowed these potential benefits, confining MNG to niche applications like scientific in tools such as Bio-Formats, where it handles multi-frame data but remains unsuitable for general web use.

Comparison with Competing Formats

Multiple-image Network Graphics (MNG) was designed as a more advanced alternative to the Graphics Interchange Format (GIF), offering support for 24-bit color depth, alpha transparency, and progressive display, which GIF lacks due to its limitation to 256 colors and binary transparency only. MNG achieves better compression for complex images through its integration with JPEG Network Graphics (JNG) for lossy elements, resulting in smaller file sizes compared to GIF for high-quality animations, though GIF's simplicity and widespread legacy support have kept it dominant despite the expiration of its LZW patent in 2004. In contrast to Animated Portable Network Graphics (APNG), introduced by Mozilla in 2004, MNG is a standalone format with a distinct file signature and MIME type (video/x-mng), requiring separate decoders and lacking backward compatibility with static PNG viewers, whereas APNG embeds animation data within standard PNG files, allowing non-supporting software to display the first frame as a static image. APNG provides similar capabilities to MNG for 24-bit RGB with 8-bit alpha but with a simpler specification tailored for web use, leading to broader adoption in browsers like Firefox, Chrome, and Safari since the mid-2010s. In June 2025, the World Wide Web Consortium (W3C) elevated APNG to official status within the PNG 3.0 specification, formalizing its integration and further marginalizing MNG by standardizing animation directly in the PNG ecosystem without needing a new format. For vector-based animations, (SVG) serves as a competing alternative, enabling resolution-independent scaling and interactive effects through XML, which suits web graphics requiring adaptability across devices, unlike MNG's raster focus. Modern raster options like animated , introduced by in 2010, offer superior for web animations, achieving up to 30% smaller files than equivalent or MNG while supporting transparency, though at the cost of potential quality loss in some scenarios. For lightweight web effects, and libraries provide programmatic control without dedicated file formats, reducing bandwidth needs for simple loops or transitions. APNG and other alternatives have prevailed over MNG primarily due to MNG's greater implementation complexity—requiring larger libraries and full format overhauls—compared to 's seamless PNG compatibility, which eased integration into existing tools and browsers. The 2025 W3C PNG update, incorporating native support alongside features like HDR, has solidified this shift, rendering MNG's advanced but underutilized features obsolete in most web contexts.
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