HEIC Image Format: A Comprehensive Report
Technical Specifications of HEIC
Format and Structure: HEIC stands for High Efficiency Image Container, and it is essentially the container file format for images under the HEIF standard (High Efficiency Image File Format) developed by MPEG. HEIC is built on the ISO Base Media File Format structure (the same foundation as MP4 video files), meaning image data and metadata are organized in a series of boxes/atoms within the file. Each HEIC file begins with a file type box (ftyp) identifying it as an HEIF/HEIC file via a brand code (for example, heic or heix). The .heic extension is commonly used for HEVC-compressed HEIF images (single images), while .heics may denote image sequence files (multiple images). Apple devices use the .heic extension for photos and pronounce it "heek".
Compression Codec: HEIC uses the High Efficiency Video Coding (HEVC, also known as H.265) codec for image compression by default. In practice, a HEIC image is like a single intra-coded video frame encoded with HEVC's advanced compression algorithms. This modern codec allows HEIC to store images in half the file size of an equivalent quality JPEG. HEVC-based still-image encoding (sometimes called the HEVC Main Still Picture profile) offers much more efficient compression than the older JPEG's DCT-based compression. HEIC also supports lossless compression modes – the HEIF specification allows images to be saved without quality loss, though most HEIC photos (such as those from phones) are saved with lossy compression for maximum size savings.
Color Depth and Quality: HEIC supports deep color and high dynamic range imaging. While JPEG is limited to 8-bit per channel (256 levels per color, ~16.7 million colors total), HEIC images can be 10-bit, 12-bit, or even 16-bit per color channel. In practical use, many HEIC photos are 10-bit, which allows over a billion possible colors and enables true HDR photos with extended dynamic range and smoother gradients. For example, recent smartphones and high-end cameras use 10-bit HEIF/HEIC to capture more vibrant HDR images with wide color gamuts (such as Rec.2020 or P3 color primaries).
Compression Methods and Efficiency
HEIC achieves its high compression efficiency primarily through the power of the HEVC (H.265) compression algorithm. HEVC was designed for high-resolution video (4K and beyond), and it brings those advanced techniques to still image coding in HEIC. Key factors in how HEIC maintains quality while reducing file size include:
- Advanced Intra-Frame Compression: HEVC uses more flexible and complex intra-frame compression than JPEG's 1990s-era algorithm. Instead of fixed 8×8 blocks with DCT (discrete cosine transform) as in JPEG, HEVC can use variable block sizes up to 64×64 pixels and many more intra-prediction modes to find the most efficient way to represent an image region.
- Efficient Entropy Coding: HEVC employs modern entropy coding (like CABAC – Context-Adaptive Binary Arithmetic Coding) which packs bits more efficiently than the older Huffman coding used in JPEG. This further squeezes the image data without losing detail, contributing to the significant bitrate reduction.
- High Precision and Less Data Loss: Because HEIC supports higher bit depth and more sophisticated color compression, it retains fine details and color gradients better than JPEG. For example, an HEIC photo can preserve subtle variations in skies or shadows without banding, even at high compression, thanks to 10-bit color and HEVC's precision.
- Multiple Image Compression: When multiple images are stored in one HEIC container (such as burst shots or an image sequence), the format can employ inter-frame compression similar to a video codec. Redundant information between frames can be stored once and reused, drastically cutting down total size for sequences.
- Optional Lossless Mode: While HEIC is usually used as a lossy format, HEIF also supports a lossless compression mode. In lossless mode, the image is compressed such that it can be decoded to an exact pixel-for-pixel copy of the original.
All these methods mean that HEIC can retain higher image quality at a fraction of the file size compared to older formats. Users typically observe that HEIC images maintain clarity and detail even at aggressive compression settings, where an equivalent JPEG would show noticeable degradation. One source notes that HEIC achieves roughly a 50% file size reduction with no visible quality loss – effectively doubling storage capacity for photos.
Comparison with JPEG, PNG, and WebP
HEIC is one of the "next-generation" image formats, and it differs from older formats like JPEG and PNG, as well as fellow modern format WebP, in several ways. The following table provides a high-level comparison of HEIC vs. JPEG vs. PNG vs. WebP in terms of compression, quality, and features:
| Feature | JPEG (JPG) | PNG | WebP | HEIC (HEIF/HEVC) |
|---|---|---|---|---|
| Compression Type | Lossy only (DCT-based) | Lossless only | Both lossy and lossless | Both lossy and lossless |
| Typical File Size | Baseline standard | Very large for photos | ~25–35% smaller than JPEG | ~50% smaller than JPEG |
| Color Depth | 8-bit per channel | Up to 16-bit per channel | 8-bit per channel | 8, 10, 12, or 16-bit |
| Transparency | No | Yes | Yes | Yes |
| Animation | No | No (APNG extension) | Yes | Yes |
Comparison Highlights: In summary, HEIC offers superior compression and more features than the older JPEG and PNG formats, albeit with less universal support. Compared to JPEG, HEIC produces much smaller files for the same quality – often around 50% size savings. This is a major advantage in storage and bandwidth. HEIC also supports transparency and advanced features that JPEG cannot (JPEG has no alpha channel or multi-frame capability). Additionally, HEIC's support for 10-bit color means it can store HDR images with far more color detail than JPEG's 8-bit limitation.
Device and Software Support for HEIC
Despite its technical advantages, HEIC's adoption has been uneven. Support varies across different operating systems, devices, and applications. Below is an overview of where HEIC is supported natively, where it requires add-ons, and where it's not supported:
- Apple Ecosystem: Apple was the first major adopter of HEIC. iOS 11 and later (since the iPhone 7 in 2017) save photos in HEIC format by default. All modern iPhones and iPads (iOS/iPadOS) have native support: you can view, edit, and share HEIC photos seamlessly in the Photos app or any app using the system image picker. macOS High Sierra (10.13) and later on Macs likewise have built-in support.
- Windows: Microsoft added HEIC support starting with Windows 10 (version 1803, released 2018), but it's not enabled out-of-the-box by default. Windows uses a system of extensions: users must install the HEIF Image Extensions (free) from Microsoft, and for HEVC decoding Windows 10 also requires the HEVC Video Extensions (a small paid add-on in the Store).
- Android: Android's support for HEIC/HEIF has improved over time. Basic HEIF support (for decoding images) was added in Android 8.0 Oreo. Full support for capturing HEIC photos arrived in Android 10 (2019) on devices with the proper hardware encoders.
- Web Browsers: At present, web browser support for HEIC is very limited. As of mid-2024, Apple Safari (on macOS and iOS) is the only major browser that can display HEIC images natively. Other browsers like Chrome, Firefox, and Edge do not support using HEIC files in <img> tags or CSS by default.
Conversion and Usage in Workflows
Given the patchy support, converting HEIC images to more common formats is a frequent task. Here are tools and methods for converting and using HEIC files in typical workflows:
- Within Apple Ecosystem: If you stay within Apple devices, you usually don't need to convert – macOS and iOS handle HEIC transparently. However, when sharing or exporting out, Apple provides automatic conversion options. For example, when you AirDrop a photo to an older Mac or send via iMessage to an Android, the system may convert the HEIC to JPEG on-the-fly for compatibility.
- Windows Conversion: On Windows 10/11, once you have the HEIF and HEVC extensions installed, you can open HEIC images in the Photos app or even MS Paint. A simple method to convert one image is to open it in Paint and then use File > Save As to save a copy as JPEG or PNG.
- Using Adobe or Other Software: If you have Adobe Photoshop, you can open HEIC files (ensure the Windows codecs are installed if on Windows). Once opened, you can simply Save As or export to your desired format. Adobe Lightroom Classic can import HEIC images and you can then export them as JPEG, DNG, etc. with your edits.
- Online Converters: Numerous free online tools can convert HEIC to JPEG/PNG; for example, browser-based services where you upload .heic files and get back JPEGs. These are handy if you just have a few images and are on a device that doesn't support HEIC.
Conclusion
HEIC is a technically advanced image format that brings high efficiency and new capabilities to photography. It offers superior compression (smaller file sizes) while retaining excellent quality, support for deep color and HDR, the ability to hold multiple images or even video in one file, and features like transparency and rich metadata that go beyond what JPEG and PNG can do.
However, as a new format, HEIC comes with challenges. Compatibility is the biggest hurdle – not all software and platforms can handle HEIC natively, especially outside of the Apple ecosystem. This has led to a period where users and professionals often need to convert HEIC files to more ubiquitous formats like JPEG for broader sharing and use.
Looking forward, as operating systems and software continue to integrate HEIC support – and with even newer formats like AVIF gaining traction – we can expect the image format landscape to evolve. HEIC has established itself firmly, thanks in large part to Apple's adoption and the format's genuine benefits. It may not completely replace JPEG in the immediate future, but it has carved out an important role in imaging.