Here’s a quick way to convert SVG to PNG with transparent background
convert -background none image.svg image.png
Adjust size
If you want to scale the image to a larger size without antialiasing (which makes the image look fuzzy), you can add the density parameter, like this:
convert -density 200 -background none image.svg image.png
Simply increase the density value to increase the image size.
To install ImageMagick on OS X with Homebrew:
brew install imagemagick
For Ubuntu:
sudo apt-get install imagemagick