ImageMagick SVG to transparent PNG flags

For ImageMagick, -background none preserves transparency (the default is white) and -density controls raster resolution before rasterizing the SVG, not after. So magick -background none -density 600 input.svg out.png renders crisply at high DPI with a real alpha channel; if the SVG only uses black strokes/fills, the output channels will be graya rather than rgba, but transparency still works.