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>

src/IO/ImageExporter.h

@@ -0,0 +1,47 @@
+#pragma once
+#include "IO/ProjectStore.h"
+#include <QByteArray>
+#include <QImage>
+#include <functional>
+#include <stdexcept>
+
+class ExportError : public std::runtime_error {
+public:
+    enum class Kind { tooLarge, render, encode };
+    explicit ExportError(Kind kind);
+    const Kind kind;
+};
+
+// Swift's CancellationError: a newer request superseded this one.
+class CancellationError : public std::exception {};
+
+struct ExportRaster {
+    QImage image;
+    // Pixels per inch.
+    double resolution = 72;
+};
+
+struct JPEGOptions {
+    double quality = 0.85;
+    // The matte behind transparent pixels.
+    double red = 1;
+    double green = 1;
+    double blue = 1;
+    bool operator==(const JPEGOptions &) const = default;
+};
+
+struct JPEGResult {
+    QByteArray data;
+    // Decoded from `data`, at most 1000 pixels a side.
+    QImage preview;
+};
+
+namespace ImageExporter {
+ExportRaster render(const ProjectSnapshot &snapshot);
+QByteArray pngData(const ProjectSnapshot &snapshot);
+// Stops at Swift's three points once `cancelled` says so.
+JPEGResult jpeg(const ExportRaster &raster, const JPEGOptions &options, const std::function<bool()> &cancelled = {});
+void exportPNG(const ProjectSnapshot &snapshot, const QString &path);
+// Replaces the file in one step, or not at all.
+void write(const QByteArray &data, const QString &path);
+}