/<w>/<h>/hex/<hex> - generate a solid color
/<w>/<h>/hex/<hex>/<hex> - generate a color gradient
/<w>/<h>/rgb/<r>/<g>/<b> - generate a solid color
/<w>/<h>/rgb/<r>/<g>/<b>/<r2>/<g2>/<b2> - generate a color gradient
/<w>/<h>/rgba/<r>/<g>/<b>/<a> - generate a solid color
/<w>/<h>/rgba/<r>/<g>/<b>/<a>/<r2>/<g2>/<b2>/<a2> - generate a color gradient