OmaPhoto 1.0.0: the Linux port of Compositor

A layered image editor for Linux and Omarchy, ported from Compositor
(github.com/robbietilton/Compositor), whose Swift source is its
specification. It reads and writes Compositor's .comp projects.

Packages for Ubuntu, Fedora and Arch come from the release workflow;
scripts/install/ holds one install script per distribution family,
and flake.nix serves NixOS.

Co-Authored-By: Claude <noreply@anthropic.com>

kernels/AdjustPixels.h

@@ -0,0 +1,19 @@
+#ifndef AdjustPixels_h
+#define AdjustPixels_h
+#include <stdint.h>
+#include <stddef.h>
+// Gradient Map on premultiplied RGBA pixels (4 bytes per pixel, `stride` bytes per row): each pixel's
+// luminance picks a color from `table` (256 × 3 straight sRGB bytes, darkest first). Alpha is kept and
+// fully transparent pixels are left alone.
+void adjust_gradient_map(uint8_t *rgba, size_t width, size_t height, size_t stride, const uint8_t *table);
+// Film grain on premultiplied RGBA pixels: the same brightness change on all three channels, strongest
+// in the midtones. `amount` is 0–100, `size` the grain's scale in document units, and `roughness`
+// (0–100) mixes in per-unit noise. Pixel (x, y) sits at (originX + (x + 0.5) × unitsPerPixel,
+// originY + (y + 0.5) × unitsPerPixel), and its grain depends only on that position and `seed`, so a
+// piece of an image gets the same grain as that part of the whole.
+void adjust_grain(uint8_t *rgba, size_t width, size_t height, size_t stride, double amount, double size,
+                  double roughness, uint32_t seed, double originX, double originY, double unitsPerPixel);
+// After resampling with a filter that rings (Lanczos), premultiplied RGBA colors can exceed their alpha;
+// this clamps each channel back to its pixel's alpha. `count` is the number of pixels.
+void rgba_clamp_premultiplied(uint8_t *rgba, size_t count);
+#endif