I've bumped the version to 4.3 (was 4.2.17), added native ARM64 support, and optimized a whole bunch of important rendering code paths. In addition, the quality of selection antialiasing has been improved by using a 4x4 super sampling filter, whereas before it was 3x3. There should be no performance loss because it is now optimized to use vectorized SSSE3 instructions ("SIMD") on x86/x64 systems.
I'm in the process of making this available via the built-in updater. Should be just an hour or so. I'll update this post to remove this paragraph when that's complete.
Direct download links:
Any CPU (x64, x86, ARM64): https://www.getpaint.net/files/zip/test/paint.net.4.300.7878.42294.install.anycpu.fdd.aot.zip
Intel/AMD 64-bit (x64): https://www.getpaint.net/files/zip/test/paint.net.4.300.7878.42294.portable.x64.scd.aot.zip
Intel/AMD 32-bit (x86): https://www.getpaint.net/files/zip/test/paint.net.4.300.7878.42294.portable.x86.scd.aot.zip
ARM64 (new!): https://www.getpaint.net/files/zip/test/paint.net.4.300.7878.42294.portable.arm64.scd.aot.zip
Changes since 4.2.17 alpha build 7858:
New: ARM64 is now natively supported
Improved: Many areas of the app have been optimized to use SIMD (SSE2/3/4.1, AVX2) on x86/x64
Drawing on an image with a large number of layers is faster
Drawing with the Gradient Tool's alpha mode is faster
Drawing with the Recolor tool is faster
Drawing with the Erase or Clone Stamp tool is faster when using a color whose alpha value is less than 255
Drawing with the Overwrite blend mode is faster
Drawing with the Shapes tool is faster, due to improved compositing performance
Drawing with a brush tool without antialiasing is faster
Tile compression has lower overhead due to being optimized for SSE2 and AVX2
Working with complex selections is faster
Many other optimizations all throughout the application and rendering engine
Improved: Selection antialiasing quality is now better by way of using a 4x4 super sampling filter instead of 3x3. The code has also been optimized to use SSSE3 on x86/x64.
Improved: Performance should be significantly better on systems without HyperThreading (by reserving 1 core for the UI), and also a bit better on systems with it (by utilizing more of the logical cores)
Improved: Effect and File Type plugins can now be organized into folders -- the plugin loader will recursively search for DLLs up to 1 folder deep
Fixed: There were some issues with zooming in/out using the keyboard, where the anchoring (centering) point was not calculated correctly, causing the canvas to drift in the wrong direction.
Fixed: If a download fails in the Prerequisites Installer, it will retry and resume up to 10 times, thus greatly improving its reliability for downloading things like .NET 5 and the Visual C++ Runtime
Changed: A processor that supports SSSE3 (yes 3 S's) is now required for x86/x64 systems (previously only SSE2 was required). All CPUs released since about 2006 (e.g. Core 2 Duo) support this.
Known Issue: Due to crashing, GPU accelerated effects (Gaussian Blur, Motion Blur, Radial Blur) on ARM64 will actually use the CPU for rendering.