iolib.py 文件源码

def ds_getma_sub(src_ds, bnum=1, scale=None, maxdim=1024.):    
    """Load a subsampled array, rather than full resolution

    This is useful when working with large rasters

    Uses buf_xsize and buf_ysize options from GDAL ReadAsArray method.

    Parameters
    ----------
    ds : gdal.Dataset 
        Input GDAL Datset
    bnum : int, optional
        Band number
    scale : int, optional
        Scaling factor
    maxdim : int, optional 
        Maximum dimension along either axis, in pixels

    Returns
    -------
    np.ma.array    
        Masked array containing raster values
    """
    #print src_ds.GetFileList()[0]
    b = src_ds.GetRasterBand(bnum)
    b_ndv = get_ndv_b(b)
    ns, nl = get_sub_dim(src_ds, scale, maxdim)
    #The buf_size parameters determine the final array dimensions
    b_array = b.ReadAsArray(buf_xsize=ns, buf_ysize=nl)
    bma = np.ma.masked_values(b_array, b_ndv)
    return bma

#Note: need to consolidate with warplib.writeout (takes ds, not ma)
#Add option to build overviews when writing GTiff
#Input proj must be WKT