img=;

Graphics@Raster[ImageData[img] /. {r_,g_,b_} :> {0,g,b}]

Dimensions[ImageData[img]]

Graphics@Raster@Partition[SortBy[Join@@ImageData[img], Norm],720]

Graphics@Raster@Partition[SortBy[Join@@ImageData[img]/. {r_,g_,b_} :> {0,g,b}, Norm],720]