Add script to generate portable AppImage

AppDir/usr/share/applications/msupcm.desktop

@@ -0,0 +1,6 @@
+[Desktop Entry]
+Type=Application
+Name=MSUPCM
+Exec=msupcm
+Icon=msupcm
+Categories=AudioVideo;Utility;

README.md

@@ -49,4 +49,30 @@ then simply run
 make
 ```
 
-from the top-level repo directory.
+from the top-level repo directory.
+
+### AppImage
+
+It is also possible to build a portable **AppImage** of `msupcm++`.  
+This bundles the binary together with its dependencies into a single executable file  
+that can be run on most modern Linux distributions without installing libraries manually.
+
+From the top-level repo directory, run:
+
+```
+chmod +x make-appimage.sh  
+./make-appimage.sh
+```
+
+After the build finishes, an AppImage will be created in the same directory,  
+for example:
+
+```
+MSUPCMPLUSPLUS-x86_64.AppImage
+```
+
+You can run it directly:
+
+```
+./MSUPCMPLUSPLUS-x86_64.AppImage tracks.json
+```

make-appimage.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+set -e
+
+APP=msupcm
+VERSION=v1.0RC3
+
+# 1. Compile normally with your main Makefile
+make -C msupcm++ clean || true
+make
+
+# 2. Prepare AppDir
+rm -rf AppDir
+mkdir -p AppDir/usr/bin
+mkdir -p AppDir/usr/share/applications
+mkdir -p AppDir/usr/share/icons/hicolor
+
+# Copy binary
+cp msupcm++/msupcm AppDir/usr/bin/
+
+# Create .desktop file
+cat > AppDir/usr/share/applications/$APP.desktop <<EOF
+[Desktop Entry]
+Type=Application
+Name=MSUPCMPLUSPLUS
+Exec=msupcm
+Icon=msupcm
+Categories=AudioVideo;Utility;
+EOF
+
+# Copy icons from res/ if they exist, otherwise generate placeholder
+ICON_SRC_DIR=res/icons/hicolor
+
+if [ -d "$ICON_SRC_DIR" ]; then
+    echo "Copying icons..."
+    for SIZE_PATH in "$ICON_SRC_DIR"/*; do
+        SIZE=$(basename "$SIZE_PATH") 
+        SRC_APPS_DIR="$SIZE_PATH/apps"
+        DST_APPS_DIR="AppDir/usr/share/icons/hicolor/$SIZE/apps"
+        mkdir -p "$DST_APPS_DIR"
+        for ICON_FILE in "$SRC_APPS_DIR"/*.png; do
+            [ -f "$ICON_FILE" ] && cp "$ICON_FILE" "$DST_APPS_DIR/"
+        done
+    done
+fi
+
+# Generate placeholders if 256x256 does not exist
+PLACEHOLDER_256="AppDir/usr/share/icons/hicolor/256x256/apps/msupcm.png"
+if [ ! -f "$PLACEHOLDER_256" ]; then
+    echo "Generating 256x256 placeholder icon..."
+    mkdir -p "$(dirname "$PLACEHOLDER_256")"
+    convert -size 256x256 xc:lightgray -gravity center \
+        -pointsize 48 -draw "text 0,0 'MSU'" "$PLACEHOLDER_256"
+fi
+
+# 3. Package into AppImage
+wget -c https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage
+chmod +x linuxdeploy-x86_64.AppImage
+
+./linuxdeploy-x86_64.AppImage \
+    --appdir AppDir \
+    --desktop-file AppDir/usr/share/applications/$APP.desktop \
+    --icon-file AppDir/usr/share/icons/hicolor/256x256/apps/msupcm.png \
+    --output appimage
+