Codec Corpus

July 23, 2026 · View on GitHub

A curated collection of reference images for codec quality calibration, compression benchmarking, and format conformance testing. Maintained by Imazen.

Total repo size: ~670 MB committed, plus ~1 GB available via download scripts.

Quick Start

# Clone everything (~600 MB)
git clone https://github.com/imazen/codec-corpus.git

# Or clone just one dataset using sparse checkout
git clone --depth 1 --filter=blob:none --sparse \
  https://github.com/imazen/codec-corpus.git
cd codec-corpus
git sparse-checkout set clic2025

# Add more datasets later
git sparse-checkout add CID22 gb82-sc qoi-benchmark

Datasets at a Glance

Quality Calibration & Compression Research

Dataset	Images	Size	Resolution	License	Best For
CLIC 2025	62	219 MB	~2048px long edge	Unsplash	High-res lossy quality calibration
CID22	250	94 MB	512×512	CC BY-SA 4.0	Perceptual quality training, diverse content
imazen-26	2,160	5.9 GB (originals)	0.2–124 MP	Mostly PD/PD-own	Real-world diversity: photos, scans, screenshots, AI-gen, docs; train/val split + representative subsets
KADID-10k	81	25 MB	512×384	Pixabay	IQA research reference images
GB82	25	9.6 MB	576×576	CC0	Compact photographic benchmarking
GB82-SC	10	2.9 MB	Various (640–2940px)	CC0	Screen content & screenshot compression
QOI Benchmark	15+	39 MB+	Various (1313×2874–8008)	CC0/PD/Mixed	Web screenshots, icons, textures

Format Conformance & Edge Cases

Dataset	Files	Size	License	Best For
AVIF Conformance	137	33 MB	BSD-2/CC-BY-SA/Apache	AVIF decoder conformance, HDR, gain maps
HEIC Conformance	173	29 MB	MIT/LGPL/Various	HEIC/HEIF decoder conformance
JPEG Conformance	277	76 MB	MIT/IJG+BSD/Various	JPEG decoder conformance & robustness
JXL	188	88 MB	BSD-3-Clause	JPEG XL decoder conformance
PNGSuite	178	720 KB	Freeware	PNG decoder conformance
APNG Conformance	31	184 KB	CC0	Animated PNG conformance
GIF Conformance	39	208 KB	CC0	GIF animation conformance
TIFF Conformance	154	12 MB	MIT/CC0/libtiff/Various	TIFF decoder conformance & robustness
WebP Conformance	230	1.3 MB	Various	WebP decoder conformance
BMP Conformance	126	—	Various	BMP decoder conformance
PNM Conformance	51	260 KB	CC0	PBM/PGM/PPM/PAM conformance
Farbfeld Conformance	24	156 KB	CC0	Farbfeld decoder conformance
UltraHDR Conformance	55	32 MB	MIT/Apache/CC-BY	HDR gain map conformance (JPEG/AVIF/JXL)
RAW/DNG Conformance	—	Git LFS	CC0	Camera RAW decoder conformance
image-rs	127	4.5 MB	MIT	Multi-format edge cases
zune-image	3,434	33 MB	MIT/Apache-2.0/Zlib	Fuzz testing, decoder robustness
mozjpeg	16	1.2 MB	IJG + BSD	JPEG codec reference files
imageflow	51	7.8 MB	Various	Orientation, format conversion edge cases

Quality Calibration & Compression Research

Challenge on Learned Image Compression 2025 — High-resolution photographic images curated for compression quality research. This is the most relevant modern benchmark for lossy codec calibration, featuring large, diverse photographs at resolutions representative of modern camera output and web delivery.

Folder	Images	Size	Purpose
`clic2025/training/`	32	103 MB	Tune and calibrate encoders against these
`clic2025/final-test/`	30	116 MB	Holdout set — final evaluation only

Note: The CLIC challenge calls these "validation" and "test" respectively. We renamed "validation" → "training" because in codec development, "validation" typically implies a holdout set, which is the opposite of the intended use. See clic2025/README.md for the original naming and download links.

Resolution: ~2048px on long edge (varies from 878px to 2048px on short edge)
Format: Lossless PNG, 8-bit sRGB
Source: https://clic2025.compression.cc/
License: Unsplash License — Free for any use, no attribution required, cannot be sold unmodified or used to build a competing service.

CID22

Cloudinary Image Dataset 2022 — 250 diverse images selected by Cloudinary for perceptual quality research. This dataset spans a wider variety of content types than most photographic benchmarks: portraits, landscapes, text, graphics, medical imagery, scientific plots, and more. The 512px size makes it fast to process while remaining large enough for meaningful perceptual quality evaluation.

For compression benchmarking, CID22 is one of the best choices available: it was specifically designed for this purpose, its diversity avoids the over-fitting that plagues small homogeneous corpora, and the training/validation split enables principled evaluation.

Folder	Images	Purpose
`CID22/CID22-512/validation/`	41	Held out for validation
`CID22/CID22-512/training/`	209	Model training and calibration

Resolution: 512×512, 8-bit sRGB
Source: https://github.com/Cloudinary/CID22
License: CC BY-SA 4.0 — Free for any use, attribution required. Derivative works must use the same license.

imazen-26

21-category real-world corpus — 2,160 images / 5.9 GB spanning the hard cases codecs trip on: photographic noise, hard-edged vector graphics, bilevel scan texture, dense text, large flat regions. Mixes real photographs, stock photography, artwork reproductions, born-digital government documents, manuscript scans, synthetic charts, UI screenshots, and AI-generated graphics. ~2,128 of 2,160 files are public-domain or PD-own.

Hosted on R2, not in this repo — full public-URL index, train/val split manifests, representative-subset selections, and a cropscale set are all at imazen-26/ACCESS.md. Two layers are available:

Layer	Size	Notes
Raw originals (jpg/heic/png/dng)	6.99 GB	Home-state GPS stripped; travel-location GPS intentionally retained as landmark metadata — see privacy note in `ACCESS.md` before use
PNG derivatives (codec-test-ready)	16 GB	SDR + HDR renders, no EXIF/GPS at all

Resolution: 0.2–124 MP, varies by category
Source: lilith's own photography + Unsplash + Art Institute of Chicago + The Met + US federal agencies (NPS/EPA/NOAA) + Internet Archive + AI-generated
License: mixed per-folder — see imazen-26/README.md for the full breakdown (PD-own, PD, PD-USGov, Unsplash License, CC0); 32 mobile-screenshot files are screenshot-unverified, excluded from redistribution

KADID-10k

Konstanz Artificially Distorted Image quality Database — 81 pristine reference images used for image quality assessment (IQA) research. Created at the University of Konstanz, this dataset is widely used for training and evaluating perceptual quality metrics. Only the pristine reference images are included here; the 10,125 distorted variants are not.

Folder	Images	Size
`kadid10k/`	81	25 MB

Resolution: 512×384, 8-bit sRGB
Format: Lossless PNG
Source: https://database.mmsp-kn.de/kadid-10k-database.html
License: Pixabay License — Free for commercial and non-commercial use, no attribution required.
Citation: H. Lin, V. Hosu and D. Saupe, "KADID-10k: A Large-scale Artificially Distorted IQA Database," 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX), Berlin, Germany, 2019, pp. 1-3, doi: 10.1109/QoMEX.2019.8743252.

GB82

GB82 Image Dataset by Gianni Rosato — A compact, purpose-built CC0 dataset for image compression algorithm development. The 25 images are selected to be challenging: fine facial details, low-contrast sky gradients, digital noise, fine textures. Optimizing for weak metrics like PSNR should not yield visually compelling results on most images.

Folder	Images	Size
`gb82/`	25	9.6 MB

Image categories:

3 portraits (2 human, 1 dog)
6 landscapes
8 closeups of inanimate objects or scenes
4 low-light shots
3 realistically rendered graphics
1 non-photographic image
Resolution: 576×576, 8-bit sRGB, D65 white point
Source: https://github.com/gianni-rosato/gb82-image-set
License: CC0 1.0 — Public domain, no restrictions.

GB82-SC

GB82 Screen Content Dataset by Gianni Rosato — Screenshots and screen content images focusing on text, UI elements, and graphics from five platforms. Screen content compresses very differently from photographic content: sharp edges, flat color regions, anti-aliased text, and high-contrast UI elements stress different codec paths. This dataset fills an important gap that photographic benchmarks miss entirely.

File	Resolution	Content
`codec_wiki.png$	2560 \times 1664	\text{Wikipedia} \text{article} \text{with} \text{text} \text{and} \text{diagrams}
$gmessages.png$	1440 \times 3088	\text{Google} \text{Messages} (\text{Android})
$graph.png$	796 \times 481	\text{Data} \text{visualization} / \text{chart}
$gui.png$	1356 \times 1132	\text{Desktop} \text{GUI} \text{elements}
$imac_dark.png$	2940 \times 1912	\text{macOS} \text{desktop} (\text{dark} \text{mode})
$imac_g3.png$	2940 \times 1912	\text{macOS} \text{desktop} (\text{light}, \text{iMac} \text{G3} \text{style})
$imessage.png$	1206 \times 2622	\text{iMessage} \text{conversation} (\text{iOS})
$terminal.png$	1646 \times 1062	\text{Terminal} / \text{command} \text{line}
$windows95.png$	640 \times 480	\text{Windows} 95 \text{desktop}
$windows.png`	2560×1392	Modern Windows desktop

Resolution: Various (640×480 to 2940×1912), 8-bit sRGB
Source: https://github.com/gianni-rosato/gb82-image-set
License: CC0 1.0 — Public domain, no restrictions.

QOI Benchmark Suite

Subsets from the QOI Benchmark Suite by Dominic Szablewski. The screenshot_web subset is committed directly to the repo; all other subsets can be fetched with the included download scripts.

Committed:

Subset	Files	Size	License	Content
`qoi-benchmark/screenshot_web/`	14	39 MB	CC0 1.0	Full-page web screenshots (amazon, apple, cnn, wikipedia, reddit, etc.)

Available via download scripts:

Subset	Files	Size	License	Content
`icon_512`	214	12 MB	Public Domain	Tango Icon Library at 512px
`icon_64`	214	1.3 MB	Public Domain	Tango Icon Library at 64px
`screenshot_game`	619	256 MB	CC BY-SA 3.0	Game screenshots from Wikimedia Commons
`textures_pk`	1004	44 MB	—	Texture pack
`textures_pk01`	115	19 MB	—	Texture pack 01
`textures_pk02`	237	99 MB	—	Texture pack 02
`textures_plants`	61	50 MB	—	Plant textures
`textures_photo`	21	37 MB	—	Photographic textures
`photo_kodak`	25	15 MB	Unrestricted	Kodak suite¹
`photo_tecnick`	101	228 MB	—	Tecnick photographic set
`photo_wikipedia`	50	85 MB	—	Wikipedia photographs
`pngimg`	189	220 MB	CC BY-NC 4.0	PNG images (non-commercial only)

# Download all subsets (~1.1 GB tarball)
cd qoi-benchmark && ./download.sh

# Download specific subsets
./download.sh icon_512 icon_64

# List available subsets
./download.sh --list

# Windows
cd qoi-benchmark
.\download.ps1
.\download.ps1 -Subsets icon_512,icon_64
.\download.ps1 -List

Source: https://qoiformat.org/benchmark/
License: Per-subset (see table above). screenshot_web is CC0. icon_* subsets are Public Domain (Tango Icon Library). screenshot_game is CC BY-SA 3.0 (Wikimedia Commons). pngimg is CC BY-NC 4.0 (non-commercial only). Other subsets have unspecified licensing in the archive.

Format Conformance & Edge Cases

AVIF Conformance

AVIF Decoder Conformance Test Suite — 137 files covering all AV1 Image File Format features, sourced from AOM test vectors.

Folder	Files	Expected Behavior
`avif-conformance/valid/`	106	MUST decode correctly
`avif-conformance/invalid/`	12	MUST reject gracefully
`avif-conformance/edge-cases/`	19	Decoder-dependent behavior

Feature coverage: All 3 AV1 profiles, YUV 4:2:0/4:2:2/4:4:4, 8/10/12-bit depth, monochrome, alpha (full/limited range), HDR (PQ), wide color gamut (P3, BT.2020), gain maps, animation, grids, film grain, transforms (rotation/mirror/crop), ICC profiles, EXIF/XMP metadata.

Sources: AOMediaCodec/av1-avif, AOMediaCodec/libavif, link-u/avif-sample-images
License: BSD-2-Clause (AOM), CC-BY-SA 4.0 (Apple/Xiph), CC-BY-NC-ND 4.0 (Netflix)

HEIC Conformance

HEIC/HEIF Decoder Conformance Test Suite — 173 files covering the High Efficiency Image File Format.

Folder	Files	Expected Behavior
`heic-conformance/valid/nokia-conformance/`	63	MUST decode correctly (⚠️ no explicit license)
`heic-conformance/valid/dsoprea-exif/`	4	MUST decode correctly
`heic-conformance/valid/libheif-testdata/`	90	MUST decode correctly
`heic-conformance/invalid/`	8	MUST reject gracefully
`heic-conformance/edge-cases/`	5	Decoder-dependent behavior

Coverage: HEIC still images, grid images (iPhone-style multi-tile), alpha channel, EXIF metadata, thumbnails, multiple images per file, overlays, stereo, sequences, edit lists.

⚠️ License note: Nokia conformance files (63 files, the most feature-complete) have no explicit license. Use for internal testing only until clarified. dsoprea samples are MIT. libheif test data is LGPL-3.0.

Sources: nokiatech/heif_conformance, dsoprea/heic-exif-samples, strukturag/libheif
License: No license (Nokia) / MIT (dsoprea) / LGPL-3.0 (libheif)

JPEG Conformance

JPEG Decoder Conformance Test Suite — Files organized by expected decoder behavior, designed for systematic testing of JPEG decoders.

Folder	Files	Expected Behavior
`jpeg-conformance/valid/`	41	MUST decode correctly
`jpeg-conformance/invalid/`	116	MUST reject gracefully
`jpeg-conformance/non-conformant/`	40	MAY reject or recover
`jpeg-conformance/crash-repro/`	78	Crash reproducers from upstream decoders

valid/ — Reference JPEG images including camera samples from 12 manufacturers, restart intervals, CMYK/YCCK color spaces, and various sampling configurations.

invalid/ — Crash tests and malformed files from imagetestsuite and fuzzing. Decoders must not crash or hang on these.

non-conformant/ — Files that violate the JPEG spec but are common in the wild:

truncated/ — Files cut at various stream positions
extraneous-data/ — Extra bytes in unexpected locations
marker-quirks/ — Unusual marker sequences (e.g., multiple 0xFF before EOI)
metadata-quirks/ — ICC profile chunk issues (ordering, duplicates, missing chunks)
progressive-quirks/ — Progressive scan encoding edge cases

Each non-conformant file has a companion .txt file explaining the defect and expected strict vs. lenient decoder behavior.

Sources: See jpeg-conformance/SOURCES.md for full per-file attribution
License: MIT / IJG+BSD / Various (per source)

JXL

JPEG XL Test Suite — Comprehensive coverage of JPEG XL decoder features and conformance.

Folder	Files	Size	Purpose
`jxl/conformance/`	39	6.2 MB	Official libjxl conformance tests
`jxl/features/`	128	81 MB	Feature-specific test images
`jxl/edge-cases/`	13	332 KB	Minimal and boundary-condition tests

Feature coverage:

Encoding: Lossless (modular), lossy (VarDCT), progressive
Color: 8/12/16/32-bit depth, sRGB, linear, grayscale, CMYK
HDR: PQ and HLG transfer functions
Animation: Multi-frame, variable timing, splines
Alpha: Premultiplied, non-premultiplied, blend modes
Features: EXIF orientation, patches, ICC profiles, JPEG reconstruction
Source: https://github.com/libjxl/libjxl, https://github.com/libjxl/conformance
License: BSD-3-Clause

PNGSuite

Official PNG Conformance Test Suite by Willem van Schaik — Covers all PNG features for decoder conformance testing.

Folder	Files	Size
`pngsuite/`	176	720 KB

Coverage:

Bit depths: 1, 2, 4, 8, 16
Color types: grayscale, RGB, palette, grayscale+alpha, RGBA
Interlacing (Adam7), transparency (tRNS), gamma correction
Ancillary chunks: sRGB, iCCP, tEXt, sBIT, pHYs, etc.
Corrupted files for error handling
Source: http://www.schaik.com/pngsuite/
License: Freeware — free to use, copy, modify, and distribute.

APNG Conformance

Animated PNG Conformance Test Suite — 31 generated APNG files covering all animation features.

Folder	Files	Expected Behavior
`apng-conformance/valid/`	22	MUST decode correctly
`apng-conformance/invalid/`	6	MUST reject gracefully
`apng-conformance/edge/`	3	Decoder-dependent behavior

Coverage: All 3 disposal operations (none, background, previous), both blend operations (source, over), frame offsets, looping (infinite, once, N), timing variations (10ms–2s, variable), color types (RGBA, RGB, grayscale, palette), default-image-as-first-frame vs separate fallback, single-frame APNG.

Source: Generated (generate.py), Python stdlib only
License: CC0 1.0 — Public domain
Spec: APNG Specification

GIF Conformance

GIF Animation Conformance Test Suite — 39 generated GIF89a files with full LZW compression.

Folder	Files	Expected Behavior
`gif-conformance/valid/`	28	MUST decode correctly
`gif-conformance/invalid/`	7	MUST reject gracefully
`gif-conformance/edge-cases/`	4	Decoder-dependent behavior

Coverage: All disposal methods (none, background, previous, unspecified), transparency, timing (0-delay to 1s, variable), looping (infinite, once, N, no Netscape extension), local vs global color tables, interlacing, frame offsets, canvas/frame geometry, GIF87a vs GIF89a, comment/plain-text extensions.

Source: Generated (generate.py), Python stdlib only (includes complete LZW encoder)
License: CC0 1.0 — Public domain

TIFF Conformance

TIFF Decoder Conformance Test Suite — 154 files covering comprehensive TIFF feature combinations, sourced from libtiff, image-tiff, and image-rs test suites.

Folder	Files	Size	Purpose
`tiff-conformance/valid/`	145	12 MB	MUST decode correctly
`tiff-conformance/edge-cases/`	5	64 KB	Uncommon but valid features
`tiff-conformance/robustness/`	4	24 KB	Malformed files — MUST reject gracefully

Coverage:

Color types: grayscale, grayscale+alpha, RGB, CMYK, palette, YCbCr, LogLuv
Bit depths: 1–64 bit integer and float (f16, f32, f64)
Compression: uncompressed, LZW, deflate, PackBits, CCITT fax3/fax4, JPEG, old JPEG, zstd, WebP, LogLuv
Organization: stripped, tiled (square/rectangular/oversized), planar
Predictors: none, horizontal, floating-point
Byte order: little-endian and big-endian
Format: classic TIFF and BigTIFF
Features: EXIF/GPS, XMP, SubIFDs, multi-page, extra samples, GeoTIFF
Sources: See tiff-conformance/SOURCES.md for per-file attribution
License: MIT / CC0 / libtiff (permissive) / Various (per source)

WebP Conformance

WebP Decoder Conformance Test Suite — 225+ synthetic test files plus real-world WebP images.

Folder	Files	Expected Behavior
`webp-conformance/valid/`	225+	MUST decode correctly

Source: Generated (RFC 6386 parameter space) + real-world samples
License: Various (per source)

BMP Conformance

BMP Decoder Conformance Test Suite — 126 files covering BMP format variants.

Folder	Files	Expected Behavior
`bmp-conformance/valid/`	—	MUST decode correctly
`bmp-conformance/invalid/`	—	MUST reject gracefully
`bmp-conformance/non-conformant/`	—	MAY reject or recover

Sources: See bmp-conformance/SOURCES.md for per-file attribution
License: Various (per source)

PNM Conformance

PNM/PAM Decoder Conformance Test Suite — 51 generated files covering all 7 Netpbm sub-formats.

Folder	Files	Expected Behavior
`pnm-conformance/valid/pbm/`	10	PBM P1 (ASCII) + P4 (binary) — MUST decode
`pnm-conformance/valid/pgm/`	8	PGM P2 (ASCII) + P5 (binary) — MUST decode
`pnm-conformance/valid/ppm/`	11	PPM P3 (ASCII) + P6 (binary) — MUST decode
`pnm-conformance/valid/pam/`	6	PAM P7 (all tuple types) — MUST decode
`pnm-conformance/invalid/`	10	MUST reject gracefully
`pnm-conformance/edge-cases/`	6	Decoder-dependent behavior

Coverage: All magic numbers (P1–P7), 8-bit and 16-bit, comments in headers, maxval edge values (0, 1, 65535, 70000), truncated data, CRLF line endings, concatenated streams, overflow dimensions.

Source: Generated (generate.py), Python stdlib only
License: CC0 1.0 — Public domain
Spec: Netpbm format specification

Farbfeld Conformance

Farbfeld Decoder Conformance Test Suite — 24 generated files for the suckless.org image format.

Folder	Files	Expected Behavior
`farbfeld-conformance/valid/`	12	MUST decode correctly
`farbfeld-conformance/invalid/`	9	MUST reject gracefully
`farbfeld-conformance/edge-cases/`	3	Decoder-dependent behavior

Coverage: Various dimensions (1x1 to 1000x1), solid colors, gradients, checkerboards, alpha channel variants, bad magic, truncated headers/pixels, zero dimensions, extra trailing data.

Source: Generated (generate.py), Python stdlib only
License: CC0 1.0 — Public domain
Spec: Farbfeld specification

UltraHDR Conformance

UltraHDR / Gain Map Conformance Test Suite — 55 files covering HDR gain maps across JPEG, AVIF, and JXL.

Folder	Files	Expected Behavior
`ultrahdr-conformance/valid/jpeg/`	43	MUST decode correctly
`ultrahdr-conformance/valid/avif/`	—	(empty — no freely-licensed samples yet)
`ultrahdr-conformance/valid/jxl/`	—	(empty — no freely-licensed samples yet)
`ultrahdr-conformance/invalid/`	5	MUST reject gracefully
`ultrahdr-conformance/edge-cases/`	3	Decoder-dependent behavior

Sources include Google's libultrahdr benchmark/test images, Pixel phone UltraHDR samples, and the Awesome-Gain-Maps collection. Covers ISO 21496-1 gain map metadata, various gain map encodings, and different transfer functions.

Sources: google/libultrahdr, NMoroney/Awesome-Gain-Maps, MishaalRahmanGH/Ultra_HDR_Samples
License: Apache-2.0 (Google) / MIT (Awesome-Gain-Maps) / CC-BY-4.0 (Pixel samples, libultrahdr test data)

RAW/DNG Conformance

Camera RAW Conformance Test Suite — RAW and DNG files from diverse camera families. Stored with Git LFS due to file sizes (10-50 MB each).

⚠️ Requires Git LFS: Run git lfs pull after cloning to download the actual RAW files.

Folder	Content
`raw-conformance/valid/bayer/`	Standard Bayer CFA (Canon CR2, Nikon NEF, Sony ARW, DNG)
`raw-conformance/valid/xtrans/`	X-Trans CFA (Fuji RAF)
`raw-conformance/valid/linear/`	Linear (demosaiced) DNG
`raw-conformance/valid/compressed/`	Lossy DNG (type 34892), JXL DNG (type 52546)
`raw-conformance/valid/mobile/`	Apple ProRAW, Android DNG
`raw-conformance/valid/proprietary/`	ORF, RW2, CR3
`raw-conformance/invalid/`	Truncated, corrupt headers, bad IFDs
`raw-conformance/edge-cases/`	Unusual bit depths, tiled, multi-page

To populate from the raw.pixls.us archive:

cd raw-conformance && ./fetch.sh

Source: raw.pixls.us CC0-licensed camera samples
License: CC0 1.0 — Public domain

image-rs

Rust image library test images — Multi-format edge cases and malformed files used by the image-rs crate.

Folder	Files	Content
`image-rs/test-images/bmp/`	60	BMP format variants and malformed files
`image-rs/test-images/gif/`	11	GIF animation edge cases
`image-rs/test-images/ico/`	7	Icon format tests
`image-rs/test-images/jpg/`	7	JPEG metadata, progressive encoding
`image-rs/test-images/png/`	22	16-bit, APNG, transparency
`image-rs/test-images/tiff/`	10	TIFF compression, predictors
`image-rs/test-images/webp/`	9	WebP lossless/lossy variants

Source: https://github.com/image-rs/image
License: MIT

zune-image

zune-image test suite — Fuzz corpus and decoder robustness tests from the zune-image project.

Folder	Files	Purpose
`zune/test-images/jpeg/`	30	JPEG edge cases (CMYK, progressive, subsampling)
`zune/fuzz-corpus/jpeg/`	1,836	Minimal JPEG fuzz inputs
`zune/fuzz-corpus/png/`	837	Minimal PNG fuzz inputs
`zune/fuzz-corpus/inflate/`	726	DEFLATE/inflate edge cases

The fuzz corpus files are minimal inputs designed to exercise specific code paths and edge cases in decoders. They are not meaningful images — they exist to catch crashes, hangs, and memory safety issues.

Source: https://github.com/etemesi254/zune-image
License: MIT OR Apache-2.0 OR Zlib (triple-licensed)

mozjpeg

Mozilla JPEG encoder test images — Reference files for JPEG codec testing, from the mozjpeg project.

File	Purpose
`testorig.ppm`	Source image (PPM format)
`testorig.jpg`	Baseline JPEG reference
`testimgari.jpg`	Arithmetic-coded JPEG
`testimgint.jpg`	Progressive JPEG
`testorig12.jpg`	12-bit JPEG
`shira_bird8.bmp`, `monkey16.ppm`	Additional source images
`test.scan`, `test1.scan`	Custom scan scripts
`test1.icc`, `test3.icc`	ICC color profiles

Source: https://github.com/mozilla/mozjpeg
License: IJG License + Modified BSD License

imageflow

Imageflow test inputs — Images used by imageflow for testing format conversion, orientation handling, and edge cases.

Folder	Files	Content
`imageflow/test_inputs/`	29	WebP, JPEG, PNG, GIF test images
`imageflow/test_inputs/orientation/`	16	EXIF orientation test set (all 8 orientations × landscape/portrait)

Includes: corrupt JPEG, color profile edge cases, transparency, gradients, whitespace handling, high-resolution (5760×4320) test image.

Source: https://github.com/imazen/imageflow
License: Various (per image)

Directory Structure

codec-corpus/
├── Quality Calibration
│   ├── clic2025/                    # CLIC 2025 (Unsplash License)
│   ├── CID22/                       # Cloudinary CID22 (CC BY-SA 4.0)
│   ├── gb82/                        # GB82 photographic (CC0)
│   ├── gb82-sc/                     # GB82 screen content (CC0)
│   ├── kadid10k/                    # KADID-10k references (Pixabay License)
│   └── qoi-benchmark/              # QOI Benchmark Suite (CC0/PD/Mixed)
│
├── Format Conformance (modern codecs)
│   ├── avif-conformance/            # AVIF — 137 files (BSD-2/CC-BY-SA/Apache)
│   │   ├── valid/, invalid/, edge-cases/, README.md
│   ├── heic-conformance/            # HEIC/HEIF — 173 files (MIT/LGPL/⚠️ Nokia unlicensed)
│   │   ├── valid/{nokia-conformance,dsoprea-exif,libheif-testdata}/
│   │   ├── invalid/, edge-cases/, README.md
│   ├── jxl/                         # JPEG XL — 188 files (BSD-3-Clause)
│   │   ├── conformance/, features/, edge-cases/
│   └── ultrahdr-conformance/        # UltraHDR gain maps — 55 files (MIT/Apache/CC-BY)
│       ├── valid/{jpeg,avif,jxl}/, invalid/, edge-cases/, README.md
│
├── Format Conformance (traditional codecs)
│   ├── jpeg-conformance/            # JPEG — 277 files (MIT/IJG+BSD/Various)
│   │   ├── valid/, invalid/, non-conformant/, crash-repro/
│   ├── pngsuite/                    # PNG — 176 files (Freeware)
│   ├── png-conformance/             # PNG edge cases — 11 files
│   ├── apng-conformance/            # APNG — 31 files (CC0, generated)
│   │   ├── valid/, invalid/, edge/, generate.py, README.md
│   ├── gif-conformance/             # GIF — 39 files (CC0, generated)
│   │   ├── valid/, invalid/, edge-cases/, generate.py, README.md
│   ├── webp-conformance/            # WebP — 230 files (Various)
│   │   ├── valid/
│   ├── tiff-conformance/            # TIFF — 154 files (MIT/CC0/libtiff/Various)
│   │   ├── valid/, edge-cases/, robustness/
│   ├── bmp-conformance/             # BMP — 126 files (Various)
│   │   ├── valid/, invalid/, non-conformant/
│   ├── pnm-conformance/             # PNM/PAM — 51 files (CC0, generated)
│   │   ├── valid/{pbm,pgm,ppm,pam}/, invalid/, edge-cases/
│   │   ├── generate.py, README.md
│   └── farbfeld-conformance/        # Farbfeld — 24 files (CC0, generated)
│       ├── valid/, invalid/, edge-cases/, generate.py, README.md
│
├── Multi-format Test Suites
│   ├── image-rs/                    # image-rs tests — 127 files (MIT)
│   ├── zune/                        # zune-image fuzz corpus — 3,434 files (MIT/Apache/Zlib)
│   ├── mozjpeg/                     # mozjpeg references — 16 files (IJG + BSD)
│   └── imageflow/                   # imageflow tests — 51 files (Various)
│
└── crate/                           # codec-corpus Rust crate source

License Summary

Every dataset includes its own license file in its directory.

Dataset	License	Commercial Use	Attribution Required	ShareAlike
CLIC 2025	Unsplash License	Yes	No	No
CID22	CC BY-SA 4.0	Yes	Yes	Yes
GB82	CC0 1.0	Yes	No	No
GB82-SC	CC0 1.0	Yes	No	No
QOI `screenshot_web`	CC0 1.0	Yes	No	No
QOI `icon_*`	Public Domain	Yes	No	No
QOI `screenshot_game`	CC BY-SA 3.0	Yes	Yes	Yes
QOI `pngimg`	CC BY-NC 4.0	No	Yes	No
KADID-10k	Pixabay License	Yes	No	No
AVIF Conformance	BSD-2/CC-BY-SA/CC-BY-NC-ND	Varies	Varies	Varies
HEIC Conformance	⚠️ Mixed/Unlicensed	Varies	Varies	—
JXL	BSD-3-Clause	Yes	No	No
PNGSuite	Freeware	Yes	No	No
APNG Conformance	CC0 1.0	Yes	No	No
GIF Conformance	CC0 1.0	Yes	No	No
TIFF Conformance	MIT/CC0/libtiff/Various	Yes	Varies	No
WebP Conformance	Various	Yes	Varies	No
BMP Conformance	Various	Yes	Varies	No
PNM Conformance	CC0 1.0	Yes	No	No
Farbfeld Conformance	CC0 1.0	Yes	No	No
UltraHDR Conformance	MIT/Apache-2.0/CC-BY-4.0	Yes	Varies	No
RAW/DNG Conformance	CC0 1.0	Yes	No	No
JPEG Conformance	MIT/IJG+BSD/Various	Yes	Varies	No
image-rs	MIT	Yes	No	No
zune-image	MIT/Apache-2.0/Zlib	Yes	No	No
mozjpeg	IJG + BSD	Yes	No	No
imageflow	Various	Yes	Varies	No

Choosing a Dataset

For lossy codec quality calibration: Use CLIC 2025 (high-res, modern photos) and CID22 (diverse content, training/validation split). These are the most representative and methodologically sound choices for modern codec evaluation.

For compact benchmarking: Use GB82 (25 challenging photos, CC0, 576×576). Fast to process, explicitly designed to resist metric gaming.

For screen content / non-photographic images: Use GB82-SC and QOI Benchmark screenshot_web. Screenshots, UI elements, text, and graphics compress very differently from photos — testing both content types is essential for any codec deployed on the web.

For decoder conformance: Use the format-specific test suites: JPEG Conformance, JXL, PNGSuite. For fuzz/robustness testing, use zune-image.

A note on Kodak

The Kodak Lossless True Color Image Suite (24 images, 768×512) is not included in this corpus. It was the de facto image compression benchmark from the 1990s through the 2010s, but decades of codec tuning against the same 24 images have made Kodak scores nearly meaningless — many codecs are specifically optimized for it. The images are also too small for modern evaluation, too homogeneous (pastoral outdoor scenes circa 1990), and offer no train/test split. Use CID22 or CLIC 2025 instead.

Color Space Normalization

All benchmark PNG images in this corpus use the standard sRGB PNG chunk to signal sRGB color space. As of February 2025, the following corrections were applied:

clic2025-1024/, clic2025/training/, imageflow/test_inputs/frymire.png: Stripped gAMA+cHRM chunks (which encoded sRGB gamma and primaries the old way) and replaced with a proper sRGB chunk.
CID22/: Stripped embedded iCCP profiles (which were sRGB IEC61966-2.1 profiles under generic names like "icc", ~2.6 KB each) and replaced with a proper sRGB chunk.
CID22/CID22-512/training/2387532.png: Had gAMA-only (no chromaticities); renamed to 2387532-srgb.png after normalization.
imageflow/test_inputs/gradients.png: Stripped iCCP (Photoshop-named sRGB profile) and replaced with sRGB chunk.

No pixel data was changed — only PNG chunk metadata was modified. This eliminates inconsistent color space signaling that can cause subtle differences in color-managed decoders and metric calculations.

Datasets not modified: gb82/, gb82-sc/, kadid10k/, qoi-benchmark/, clic2025/final-test/, webp-conformance/ (already clean — either proper sRGB chunks or no color metadata). Test/conformance directories (pngsuite/, zune/, image-rs/) were intentionally left untouched.

Contributing

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