bandCalc.py

# -*- coding: utf-8 -*-
"""
/***************************************************************************
 Batch_Hillshader
                                 A QGIS plugin  to generate a three light 
                                 exposure hillshade (shaded relief by 
                                 combining three light exposures)
  
    For more information, see the program documentation.
                                 
    If you uses as input LiDAR data, note that plugin uses LASTools library.
        See LASTools License at  <https://rapidlasso.com/lastools/>
        
    Plugin also use in LiDAR data mode FUSION LDV. 
        See FUSION LDV License at <http://forsys.cfr.washington.edu/fusion.html>
                              -------------------
        begin                : 2016-07-13
        git sha              : $Format:%H$
        copyright            : (C) 2017 by PANOimagen S.L.
        email                : info@panoimagen.com
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software: you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation, either version 3 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       * 
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program.  If not, see <https://www.gnu.org/licenses/> *
 ***************************************************************************/
"""
import numpy as np
from .plugin_utils import raster_funs

def merge_arrays(input_arrays, alpha_values,
        dem_array, no_data_value, background_value=255):
    '''Merge several input_arrays with given transparency values.

    Alpha values is a list of floats between 0 and 1 with the same size as
    the list of input_arrays.'''

    output = background_value * np.ones(input_arrays[0].shape, dtype = float)
    for array, alpha in zip(input_arrays, alpha_values):
        output = array * alpha + (1 - alpha) * output
        
    eroded_hill = raster_funs.raster_erosion(output, dem_array, no_data_value)

    return eroded_hill.astype(array[0].dtype)