[이미지 처리] 알파채널 제거

def del_alpha_channel(rgba, 
                      background=(255,255,255)):
    ''' 알파채널 제거 
    '''
    row, col, ch = rgba.shape

    if ch == 3:
        return rgba
    
    assert ch == 4, 'RGBA image has 4 channels.'
    rgb = np.zeros( (row, col, 3), dtype='float32' )
    r, g, b, a = rgba[:,:,0], rgba[:,:,1], rgba[:,:,2], rgba[:,:,3]
    a = np.asarray( a, dtype='float32' ) / 255.0
    R, G, B = background

    rgb[:,:,0] = r * a + (1.0 - a) * R
    rgb[:,:,1] = g * a + (1.0 - a) * G
    rgb[:,:,2] = b * a + (1.0 - a) * B

    return np.asarray(rgb, dtype='uint8')