SageThumbs 2k Files

What's changed

Fixed

• Black-and-white scanned pages could render as a solid black square. Some JPEG 2000 scans - the kind archive.org uses for book and map pages - store the picture as numbered colours rather than as brightness, and a blank white page is stored as "colour number 0". Our new decoder was treating that number as a brightness value, so the whitest page came out the darkest. It now reads the colour table the file provides. (issue [#11])

• The preview pane could stop refreshing after it had been sitting idle. Come back to a folder after a while, click a different picture, and the pane sometimes kept showing the previous one. Windows quietly recycles the preview pane when it has been idle, which destroys the window we draw into; we kept drawing into the window that no longer existed, so the update went nowhere and the stale picture stayed put. We now notice the window has gone and rebuild it. (issue [#11])

Added

• A built-in JPEG 2000 decoder that only decodes what the thumbnail needs. JPEG 2000 stores every image as a stack of halved resolutions, but every decoder we could reach either could not use that (ImageMagick's reduction flag returns the wrong part of the image) or did not exist in usable form - so until now a 76-megapixel scan had to be decoded in full just to make a tile. The new decoder reads only the resolution being displayed: that scan now thumbnails in 0.25 seconds instead of 4.4, and previews in 1.2 seconds instead of 5 - and the result is slightly sharper, because a true wavelet resolution level keeps detail that shrinking a full decode averages away. Verified bit-exact on lossless test images (a correct reversible decode has no rounding excuse), and anything the decoder does not support falls back to the old path automatically, so no file that rendered before renders worse.

Verified installer

• File: SageThumbs2K-Setup-1.7.5.exe
• Size: 13434438 bytes

• SHA-256: 36e61661273d544afff4f2ca4a37a18ae110e3a61bf18658844dea6bb906d07d

• ARM64 installer: SageThumbs2K-Setup-1.7.5-arm64.exe

• ARM64 SHA-256: 5437afe73d328de2bc467c7de9ea1fccbb1cd67d800e5d424399b6c02a6367f4