make_sand

width=800
height=600
sand_bg=#ffdb4d
sand_fg=#cc9900
convert -size ${width}x${height} xc:  +noise Random -virtual-pixel tile -auto-level  -channel G -threshold 15% -separate +channel -negate temp.png
convert temp.png -alpha copy -fx '#fff' sand.png
convert sand.png +level-colors black,${sand_fg} -blur 0x0.8 sand.png
convert -size ${width}x${height} canvas:${sand_bg} test.png

convert test.png sand.png -composite png32:../sand.png