Generate icon set from single source svg/png

[mahnunchik]

It would be awesome to have mac/icns behaviour extended to another targets.

User may provide single source image:

• .svg - recommended format.
• .png - minimum as 256x256 px (up to 1024x1024 px).

app-builder generates:

• .icns icon container for macOS - current implementation
• .ico for Windows (from original .svg/.png, not from .icns)
• size.png - set of icons for Linux packages.
• name-scale.png - set of icons for AppX.

---

Related issue:

• Generate Linux icons from png provided electron-userland/electron-builder#5014
• Placing Icon in Build Folder doesnt Function, also Portable icon isnt default Electron Icon electron-userland/electron-builder#4486
• Linux Ubuntu AppImage target no icon electron-userland/electron-builder#4186
• Linux icons issue electron-userland/electron-builder#2577
• AppImage icon not working electron-userland/electron-builder#4617

[mahnunchik]

Actually app-builder generates .ico container from .png image but with single size inside.

Recommended sizes inside ico should be from 16x16 to 256x256 pixels https://docs.microsoft.com/en-us/windows/win32/uxguide/vis-icons

[mahnunchik]

One more detail: app-builder can generate icons for linux from . icns but not from .svg and .png images.

.png -> . icns works as expected.

[mahnunchik]

Just for the information, to generate .ico with all required sizes from single .png you may use:

magick convert resources/icon.png \
  -resize 256x256 \
  -define icon:auto-resize="256,128,96,64,48,40,32,24,16" \
  resources/icon.ico