SageThumbs 2k Files

What's changed

Fixed

• AVIF thumbnails had shifted colours, and it was Windows, not ImageMagick. Files written by avifenc or ffmpeg came out visibly off, while the same files looked right in every other viewer. The cause was Windows' own AV1 codec: we asked it first, and it misreads the colour information libaom writes by default. Measured against two independent decoders, on a saturated test patch out of 255, it was off by 19 on 8-bit files and by 14 on 10-bit ones, where even neutral grey drifted from 128 to 139. Other viewers were fine because they do not use Windows for this.

AVIF now goes to ImageMagick except in the one case Windows demonstrably gets right (ordinary 8-bit BT.709, which is most web AVIF and stays on the fast path). On the Compact install, which has no ImageMagick, nothing changes: you keep the thumbnail you had. scripts/repro-avif-color.ps1 reproduces the whole thing from scratch. (issue [#9])

• Wide-gamut 10-bit AVIF and HEIC lost their colour profile. A separate fault the above uncovered: images decoded through ImageMagick come back at 16 bits per channel, and the colour-management step quietly skipped anything wider than 8-bit. An Adobe RGB AVIF was landing 79/255 out on a saturated patch. Those images are now colour-managed like every other format, which is the same "decoded it right, then threw the profile away" fault that was fixed for JPEG XL in 1.7.1.

• The preview pane could get stuck on the file you were looking at before. Click through a folder of files that need a slower decoder (JPEG 2000 .jp2 is the usual one) and the pane would stop keeping up: it kept showing an earlier file's picture no matter what you selected next. The pane keeps one handler alive and re-drives it per file, and when a decode came back empty nothing replaced what was already on screen. A single file on its own never hit this, which is why it went unnoticed. The pane now always clears first, so a file that fails to decode shows an empty pane instead of quietly leaving the wrong picture up. (issue [#11])

• st2k doctor claimed thumbnails were disabled when they were not. Turning off the Windows thumbnail cache (NoThumbnailCache / DisableThumbnailCache) was reported as four failures saying thumbnails are switched off. Those settings only stop Windows saving thumbnails to disk; thumbnails still work, they are just recomputed each time. They are now reported as a note rather than a problem.

• Modern game textures (.dds) now thumbnail: BC7, BC6H, BC4 and BC5. Someone left this in an uninstall comment, and they were right. SageThumbs handled the 1998 half of DDS (DXT1/DXT3/DXT5) and fell over on everything a game has actually shipped for the last decade. BC7, the format most modern colour textures use, only worked on the Full install and only by handing the file to ImageMagick. BC6H (HDR), BC4 and BC5 (masks and normal maps) did not work anywhere at all: not through SageThumbs, not through Windows' own DDS support, not through ImageMagick.

DDS is now decoded natively, so every block format from BC1 to BC7 renders, HDR textures included, on both the Full and Compact installs and without shelling out to anything. The uncompressed layouts came along with it: 16- and 32-bit float surfaces, 10-bit and 16-bit channels, the 565/5551/4444 packings, greyscale and alpha-only textures, and the decade-old DirectX 9 files that describe their pixels with bit masks.

• "Image info" reported nonsense for DDS files. The header fields were read four bytes off, so the mip-level count showed the writing tool's signature as a number (ImageMagick's files claimed 1,195,461,449 mip levels) and the compression line was garbage. It now reads the real values, tells signed BC4/BC5/BC6H apart from unsigned, and no longer mislabels a BC6H texture as BC7.

Verified installer

• File: SageThumbs2K-Setup-1.7.3.exe
• Size: 13398928 bytes

• SHA-256: 0e8da0ed53a758632fdbe265ac4dab7884e2ce25db45d2a525b9a16e5d740fe6

• ARM64 installer: SageThumbs2K-Setup-1.7.3-arm64.exe

• ARM64 SHA-256: e2a418045e331fcea57d4398df453bd3a204dc0b219539a2a97651cbc20a5caf