# -*- coding: utf-8 -*-
"""
/***************************************************************************
HUB TimeSeriesViewer
-------------------
begin : 2015-08-20
git sha : $Format:%H$
copyright : (C) 2017 by HU-Berlin
email : benjamin.jakimow@geo.hu-berlin.de
***************************************************************************/
/***************************************************************************
* *
* 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 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
"""
# noinspection PyPep8Naming
from __future__ import absolute_import
import os, sys, math, StringIO, re
import logging
logger = logging.getLogger(__name__)
from collections import defaultdict
from qgis.core import *
from qgis.gui import *
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.QtXml import QDomDocument
from PyQt4 import uic
from osgeo import gdal
import weakref
import numpy as np
jp = os.path.join
dn = os.path.dirname
from timeseriesviewer import DIR_UI
def appendItemsToMenu(menu, itemsToAdd):
"""
Appends items to QMenu "menu"
:param menu: the QMenu to be extended
:param itemsToAdd: QMenu or [list-of-QActions-or-QMenus]
:return: menu
"""
assert isinstance(menu, QMenu)
if isinstance(itemsToAdd, QMenu):
itemsToAdd = itemsToAdd.children()
if not isinstance(itemsToAdd, list):
itemsToAdd = [itemsToAdd]
for item in itemsToAdd:
if isinstance(item, QAction):
#item.setParent(menu)
a = menu.addAction(item.text(), item.triggered, item.shortcut())
a.setEnabled(item.isEnabled())
a.setIcon(item.icon())
menu.addAction(a)
s = ""
elif isinstance(item, QMenu):
item.setParent(menu)
menu.addMenu(menu)
else:
s = ""
return menu
def allSubclasses(cls):
"""
Returns all subclasses of class 'cls'
Thx to: http://stackoverflow.com/questions/3862310/how-can-i-find-all-subclasses-of-a-class-given-its-name
:param cls:
:return:
"""
return cls.__subclasses__() + [g for s in cls.__subclasses__()
for g in allSubclasses(s)]
def scaledUnitString(num, infix=' ', suffix='B', div=1000):
"""
Returns a human-readable file size string.
thanks to Fred Cirera
http://stackoverflow.com/questions/1094841/reusable-library-to-get-human-readable-version-of-file-size
:param num: number in bytes
:param suffix: 'B' for bytes by default.
:param div: divisor of num, 1000 by default.
:return: the file size string
"""
for unit in ['','K','M','G','T','P','E','Z']:
if abs(num) < div:
return "{:3.1f}{}{}{}".format(num, infix, unit, suffix)
num /= div
return "{:.1f}{}{}{}".format(num, infix, unit, suffix)
class SpatialPoint(QgsPoint):
"""
Object to keep QgsPoint and QgsCoordinateReferenceSystem together
"""
@staticmethod
def fromMapCanvasCenter(mapCanvas):
assert isinstance(mapCanvas, QgsMapCanvas)
crs = mapCanvas.mapSettings().destinationCrs()
return SpatialPoint(crs, mapCanvas.center())
@staticmethod
def fromSpatialExtent(spatialExtent):
assert isinstance(spatialExtent, SpatialExtent)
crs = spatialExtent.crs()
return SpatialPoint(crs, spatialExtent.center())
def __init__(self, crs, *args):
if not isinstance(crs, QgsCoordinateReferenceSystem):
crs = QgsCoordinateReferenceSystem(crs)
assert isinstance(crs, QgsCoordinateReferenceSystem)
super(SpatialPoint, self).__init__(*args)
self.mCrs = crs
def setCrs(self, crs):
assert isinstance(crs, QgsCoordinateReferenceSystem)
self.mCrs = crs
def crs(self):
return self.mCrs
def toPixelPosition(self, rasterDataSource, allowOutOfRaster=False):
"""
Returns the pixel position of this SpatialPoint within the rasterDataSource
:param rasterDataSource: gdal.Dataset
:param allowOutOfRaster: set True to return out-of-raster pixel positions, e.g. QPoint(-1,0)
:return: the pixel position as QPoint
"""
ds = gdalDataset(rasterDataSource)
ns, nl = ds.RasterXSize, ds.RasterYSize
gt = ds.GetGeoTransform()
pt = self.toCrs(ds.GetProjection())
if pt is None:
return None
px = geo2px(pt, gt)
if not allowOutOfRaster:
if px.x() < 0 or px.x() >= ns:
return None
if px.y() < 0 or px.y() >= nl:
return None
return px
def toCrs(self, crs):
assert isinstance(crs, QgsCoordinateReferenceSystem)
pt = QgsPoint(self)
if self.mCrs != crs:
pt = saveTransform(pt, self.mCrs, crs)
return SpatialPoint(crs, pt) if pt else None
def __reduce_ex__(self, protocol):
return self.__class__, (self.crs().toWkt(), self.x(), self.y()), {}
def __eq__(self, other):
if not isinstance(other, SpatialPoint):
return False
return self.x() == other.x() and \
self.y() == other.y() and \
self.crs() == other.crs()
def __copy__(self):
return SpatialPoint(self.crs(), self.x(), self.y())
def __str__(self):
return self.__repr__()
def __repr__(self):
return '{} {} {}'.format(self.x(), self.y(), self.crs().authid())
def findParent(qObject, parentType, checkInstance = False):
parent = qObject.parent()
if checkInstance:
while parent != None and not isinstance(parent, parentType):
parent = parent.parent()
else:
while parent != None and type(parent) != parentType:
parent = parent.parent()
return parent
def saveTransform(geom, crs1, crs2):
assert isinstance(crs1, QgsCoordinateReferenceSystem)
assert isinstance(crs2, QgsCoordinateReferenceSystem)
result = None
if isinstance(geom, QgsRectangle):
if geom.isEmpty():
return None
transform = QgsCoordinateTransform(crs1, crs2);
try:
rect = transform.transformBoundingBox(geom);
result = SpatialExtent(crs2, rect)
except:
logger.debug('Can not transform from {} to {} on rectangle {}'.format( \
crs1.description(), crs2.description(), str(geom)))
elif isinstance(geom, QgsPoint):
transform = QgsCoordinateTransform(crs1, crs2);
try:
pt = transform.transform(geom);
result = SpatialPoint(crs2, pt)
except:
logger.debug('Can not transform from {} to {} on QgsPoint {}'.format( \
crs1.description(), crs2.description(), str(geom)))
return result
def gdalDataset(pathOrDataset, eAccess=gdal.GA_ReadOnly):
"""
:param pathOrDataset: path or gdal.Dataset
:return: gdal.Dataset
"""
if not isinstance(pathOrDataset, gdal.Dataset):
pathOrDataset = gdal.Open(pathOrDataset, eAccess)
assert isinstance(pathOrDataset, gdal.Dataset)
return pathOrDataset
def geo2pxF(geo, gt):
"""
Returns the pixel position related to a Geo-Coordinate in floating point precision.
:param geo: Geo-Coordinate as QgsPoint
:param gt: GDAL Geo-Transformation tuple, as described in http://www.gdal.org/gdal_datamodel.html
:return: pixel position as QPointF
"""
assert isinstance(geo, QgsPoint)
# see http://www.gdal.org/gdal_datamodel.html
px = (geo.x() - gt[0]) / gt[1] # x pixel
py = (geo.y() - gt[3]) / gt[5] # y pixel
return QPointF(px,py)
def geo2px(geo, gt):
"""
Returns the pixel position related to a Geo-Coordinate as integer number.
Floating-point coordinate are casted to integer coordinate, e.g. the pixel coordinate (0.815, 23.42) is returned as (0,23)
:param geo: Geo-Coordinate as QgsPoint
:param gt: GDAL Geo-Transformation tuple, as described in http://www.gdal.org/gdal_datamodel.html
:return: pixel position as QPpint
"""
px = geo2pxF(geo, gt)
return QPoint(int(px.x()), int(px.y()))
def px2geo(px, gt):
#see http://www.gdal.org/gdal_datamodel.html
gx = gt[0] + px.x()*gt[1]+px.y()*gt[2]
gy = gt[3] + px.x()*gt[4]+px.y()*gt[5]
return QgsPoint(gx,gy)
class SpatialExtent(QgsRectangle):
"""
Object to keep QgsRectangle and QgsCoordinateReferenceSystem together
"""
@staticmethod
def fromMapCanvas(mapCanvas, fullExtent=False):
assert isinstance(mapCanvas, QgsMapCanvas)
if fullExtent:
extent = mapCanvas.fullExtent()
else:
extent = mapCanvas.extent()
crs = mapCanvas.mapSettings().destinationCrs()
return SpatialExtent(crs, extent)
@staticmethod
def world():
crs = QgsCoordinateReferenceSystem('EPSG:4326')
ext = QgsRectangle(-180,-90,180,90)
return SpatialExtent(crs, ext)
@staticmethod
def fromRasterSource(pathSrc):
ds = gdalDataset(pathSrc)
assert isinstance(ds, gdal.Dataset)
ns, nl = ds.RasterXSize, ds.RasterYSize
gt = ds.GetGeoTransform()
crs = QgsCoordinateReferenceSystem(ds.GetProjection())
xValues = []
yValues = []
for x in [0, ns]:
for y in [0, nl]:
px = px2geo(QPoint(x,y), gt)
xValues.append(px.x())
yValues.append(px.y())
return SpatialExtent(crs, min(xValues), min(yValues),
max(xValues), max(yValues))
@staticmethod
def fromLayer(mapLayer):
assert isinstance(mapLayer, QgsMapLayer)
extent = mapLayer.extent()
crs = mapLayer.crs()
return SpatialExtent(crs, extent)
def __init__(self, crs, *args):
if not isinstance(crs, QgsCoordinateReferenceSystem):
crs = QgsCoordinateReferenceSystem(crs)
assert isinstance(crs, QgsCoordinateReferenceSystem)
super(SpatialExtent, self).__init__(*args)
self.mCrs = crs
def setCrs(self, crs):
assert isinstance(crs, QgsCoordinateReferenceSystem)
self.mCrs = crs
def crs(self):
return self.mCrs
def toCrs(self, crs):
assert isinstance(crs, QgsCoordinateReferenceSystem)
box = QgsRectangle(self)
if self.mCrs != crs:
box = saveTransform(box, self.mCrs, crs)
return SpatialExtent(crs, box) if box else None
def spatialCenter(self):
return SpatialPoint(self.crs(), self.center())
def combineExtentWith(self, *args):
if args is None:
return
elif isinstance(args[0], SpatialExtent):
extent2 = args[0].toCrs(self.crs())
self.combineExtentWith(QgsRectangle(extent2))
else:
super(SpatialExtent, self).combineExtentWith(*args)
return self
def setCenter(self, centerPoint, crs=None):
if crs and crs != self.crs():
trans = QgsCoordinateTransform(crs, self.crs())
centerPoint = trans.transform(centerPoint)
delta = centerPoint - self.center()
self.setXMaximum(self.xMaximum() + delta.x())
self.setXMinimum(self.xMinimum() + delta.x())
self.setYMaximum(self.yMaximum() + delta.y())
self.setYMinimum(self.yMinimum() + delta.y())
return self
def __cmp__(self, other):
if other is None: return 1
s = ""
def upperRightPt(self):
return QgsPoint(*self.upperRight())
def upperLeftPt(self):
return QgsPoint(*self.upperLeft())
def lowerRightPt(self):
return QgsPoint(*self.lowerRight())
def lowerLeftPt(self):
return QgsPoint(*self.lowerLeft())
def upperRight(self):
return self.xMaximum(), self.yMaximum()
def upperLeft(self):
return self.xMinimum(), self.yMaximum()
def lowerRight(self):
return self.xMaximum(), self.yMinimum()
def lowerLeft(self):
return self.xMinimum(), self.yMinimum()
def __eq__(self, other):
return self.toString() == other.toString()
def __sub__(self, other):
raise NotImplementedError()
def __mul__(self, other):
raise NotImplementedError()
def __copy__(self):
return SpatialExtent(self.crs(), QgsRectangle(self))
def __reduce_ex__(self, protocol):
return self.__class__, (self.crs().toWkt(),
self.xMinimum(), self.yMinimum(),
self.xMaximum(), self.yMaximum()
), {}
def __str__(self):
return self.__repr__()
def __repr__(self):
return '{} {} {}'.format(self.upperLeft(), self.lowerRight(), self.crs().authid())
def qgisInstance():
"""
If existent, returns a QGIS Instance.
:return: QgisInterface | None
"""
import qgis.utils
from timeseriesviewer.main import TimeSeriesViewer
if isinstance(qgis.utils.iface, QgisInterface) and \
not isinstance(qgis.utils.iface, TimeSeriesViewer):
return qgis.utils.iface
else:
return None
def saveFilePath(text):
"""
Normalizes string, converts to lowercase, removes non-alpha characters,
and converts spaces to hyphens.
see https://stackoverflow.com/questions/295135/turn-a-string-into-a-valid-filename
:return: path
"""
import unicodedata
text = unicodedata.normalize('NFKD', text).encode('ascii', 'ignore')
text = unicode(re.sub('[^\w\s.-]', '', text).strip().lower())
text = unicode(re.sub('[-\s]+', '_', text))
return re.sub('[ ]+]','',text)
def value2str(value, sep=' '):
"""
Converts a value into a string
:param value:
:param sep:
:return:
"""
if isinstance(value, list):
value = sep.join([str(v) for v in value])
elif isinstance(value, np.array):
value = value2str(value.astype(list), sep=sep)
elif value is None:
value = ''
else:
value = str(value)
return value
# works in Python 2 & 3
class _Singleton(type):
""" A metaclass that creates a Singleton base class when called. """
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(_Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]
class Singleton(_Singleton('SingletonMeta', (object,), {})): pass
"""
#work, but require metaclass pattern
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwds):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args,**kwds)
return cls._instances[cls]
"""
class KeepRefs(object):
__refs__ = defaultdict(list)
def __init__(self):
self.__refs__[self.__class__].append(weakref.ref(self))
@classmethod
def instances(cls):
for inst_ref in cls.__refs__[cls]:
inst = inst_ref()
if inst is not None:
yield inst
def filterSubLayers(filePaths, subLayerEndings):
"""
Returns sub layers endings from all gdal Datasets within filePaths
:param filePaths:
:param subLayerEndings:
:return:
"""
results = []
if len(subLayerEndings) == 0:
return filePaths[:]
for path in filePaths:
try:
ds = gdal.Open(path)
if ds.RasterCount == 0:
for s in ds.GetSubDatasets():
for ending in subLayerEndings:
if s[0].endswith(ending):
results.append(s[0])
else:
results.append(path)
except:
pass
return results
def copyRenderer(renderer, targetLayer):
"""
Copies and applies renderer to targetLayer.
:param renderer:
:param targetLayer:
:return: True, if 'renderer' could be copied and applied to 'targetLayer'
"""
if isinstance(targetLayer, QgsRasterLayer) and isinstance(renderer, QgsRasterRenderer):
if isinstance(renderer, QgsMultiBandColorRenderer):
r = renderer.clone()
r.setInput(targetLayer.dataProvider())
targetLayer.setRenderer(r)
return True
elif isinstance(renderer, QgsSingleBandPseudoColorRenderer):
r = renderer.clone()
# r = QgsSingleBandPseudoColorRenderer(None, renderer.band(), None)
r.setInput(targetLayer.dataProvider())
cmin = renderer.classificationMin()
cmax = renderer.classificationMax()
r.setClassificationMin(cmin)
r.setClassificationMax(cmax)
targetLayer.setRenderer(r)
return True
elif isinstance(targetLayer, QgsVectorLayer) and isinstance(renderer, QgsFeatureRendererV2):
#todo: add render-specific switches
targetLayer.setRenderer(renderer)
return True
return False
def getSubLayerEndings(files):
subLayerEndings = []
for file in files:
try:
ds = gdal.Open(file)
for subLayer in ds.GetSubDatasets():
ending = subLayer[0].split(':')[-2:]
if ending not in subLayerEndings:
subLayerEndings.append(':'.join(ending))
except:
s = ""
pass
return subLayerEndings
def settings():
return QSettings('HU-Berlin', 'HUB TimeSeriesViewer')
def niceNumberString(number):
if isinstance(number, int):
return '{}'.format(number)
else:
if math.fabs(number) > 1:
return '{:0.2f}'.format(number)
else:
return '{:f}'.format(number)
def nicePredecessor(l):
mul = -1 if l < 0 else 1
l = np.abs(l)
if l > 1.0:
exp = np.fix(np.log10(l))
# normalize to [0.0,1.0]
l2 = l / 10 ** (exp)
m = np.fix(l2)
rest = l2 - m
if rest >= 0.5:
m += 0.5
return mul * m * 10 ** exp
elif l < 1.0:
exp = np.fix(np.log10(l))
#normalize to [0.0,1.0]
m = l / 10 ** (exp-1)
if m >= 5:
m = 5.0
else:
m = 1.0
return mul * m * 10 ** (exp-1)
else:
return 0.0
loadUI = lambda p : loadUIFormClass(jp(DIR_UI, p))
loadIcon = lambda p: jp(DIR_UI, *['icons',p])
#dictionary to store form classes and avoid multiple calls to read <myui>.ui
FORM_CLASSES = dict()
def loadUIFormClass(pathUi, from_imports=False, resourceSuffix=''):
"""
Loads Qt UI files (*.ui) while taking care on QgsCustomWidgets.
Uses PyQt4.uic.loadUiType (see http://pyqt.sourceforge.net/Docs/PyQt4/designer.html#the-uic-module)
:param pathUi: *.ui file path
:param from_imports: is optionally set to use import statements that are relative to '.'. At the moment this only applies to the import of resource modules.
:param resourceSuffix: is the suffix appended to the basename of any resource file specified in the .ui file to create the name of the Python module generated from the resource file by pyrcc4. The default is '_rc', i.e. if the .ui file specified a resource file called foo.qrc then the corresponding Python module is foo_rc.
:return: the form class, e.g. to be used in a class definition like MyClassUI(QFrame, loadUi('myclassui.ui'))
"""
RC_SUFFIX = resourceSuffix
assert os.path.exists(pathUi), '*.ui file does not exist: {}'.format(pathUi)
buffer = StringIO.StringIO() #buffer to store modified XML
if pathUi not in FORM_CLASSES.keys():
#parse *.ui xml and replace *.h by qgis.gui
doc = QDomDocument()
#remove new-lines. this prevents uic.loadUiType(buffer, resource_suffix=RC_SUFFIX)
#to mess up the *.ui xml
txt = ''.join(open(pathUi).readlines())
doc.setContent(txt)
# Replace *.h file references in <customwidget> with <class>Qgs...</class>, e.g.
# <header>qgscolorbutton.h</header>
# by <header>qgis.gui</header>
# this is require to compile QgsWidgets on-the-fly
elem = doc.elementsByTagName('customwidget')
for child in [elem.item(i) for i in range(elem.count())]:
child = child.toElement()
className = str(child.firstChildElement('class').firstChild().nodeValue())
if className.startswith('Qgs'):
cHeader = child.firstChildElement('header').firstChild()
cHeader.setNodeValue('qgis.gui')
#collect resource file locations
elem = doc.elementsByTagName('include')
qrcPathes = []
for child in [elem.item(i) for i in range(elem.count())]:
path = child.attributes().item(0).nodeValue()
if path.endswith('.qrc'):
qrcPathes.append(path)
#logger.debug('Load UI file: {}'.format(pathUi))
buffer.write(doc.toString())
buffer.flush()
buffer.seek(0)
#make resource file directories available to the python path (sys.path)
baseDir = os.path.dirname(pathUi)
tmpDirs = []
for qrcPath in qrcPathes:
d = os.path.dirname(os.path.join(baseDir, os.path.dirname(qrcPath)))
if d not in sys.path:
tmpDirs.append(d)
sys.path.extend(tmpDirs)
#load form class
try:
FORM_CLASS, _ = uic.loadUiType(buffer, resource_suffix=RC_SUFFIX)
except SyntaxError as ex:
logger.info('{}\n{}:"{}"\ncall instead uic.loadUiType(path,...) directly'.format(pathUi, ex, ex.text))
FORM_CLASS, _ = uic.loadUiType(pathUi, resource_suffix=RC_SUFFIX)
FORM_CLASSES[pathUi] = FORM_CLASS
#remove temporary added directories from python path
for d in tmpDirs:
sys.path.remove(d)
return FORM_CLASSES[pathUi]
def zipdir(pathDir, pathZip):
"""
:param pathDir: directory to compress
:param pathZip: path to new zipfile
"""
#thx to https://stackoverflow.com/questions/1855095/how-to-create-a-zip-archive-of-a-directory
"""
import zipfile
assert os.path.isdir(pathDir)
zipf = zipfile.ZipFile(pathZip, 'w', zipfile.ZIP_DEFLATED)
for root, dirs, files in os.walk(pathDir):
for file in files:
zipf.write(os.path.join(root, file))
zipf.close()
"""
import zipfile
relroot = os.path.abspath(os.path.join(pathDir, os.pardir))
with zipfile.ZipFile(pathZip, "w", zipfile.ZIP_DEFLATED) as zip:
for root, dirs, files in os.walk(pathDir):
# add directory (needed for empty dirs)
zip.write(root, os.path.relpath(root, relroot))
for file in files:
filename = os.path.join(root, file)
if os.path.isfile(filename): # regular files only
arcname = os.path.join(os.path.relpath(root, relroot), file)
zip.write(filename, arcname)
def initQgisApplication(pythonPlugins=None, PATH_QGIS=None, qgisDebug=False):
"""
Initializes the QGIS Environment
:return: QgsApplication instance of local QGIS installation
"""
import site
if pythonPlugins is None:
pythonPlugins = []
assert isinstance(pythonPlugins, list)
from timeseriesviewer import DIR_REPO
#pythonPlugins.append(os.path.dirname(DIR_REPO))
PLUGIN_DIR = os.path.dirname(DIR_REPO)
if os.path.isdir(PLUGIN_DIR):
for subDir in os.listdir(PLUGIN_DIR):
if not subDir.startswith('.'):
pythonPlugins.append(os.path.join(PLUGIN_DIR, subDir))
envVar = os.environ.get('QGIS_PLUGINPATH', None)
if isinstance(envVar, list):
pythonPlugins.extend(re.split('[;:]', envVar))
#make plugin paths available to QGIS and Python
os.environ['QGIS_PLUGINPATH'] = ';'.join(pythonPlugins)
os.environ['QGIS_DEBUG'] = '1' if qgisDebug else '0'
for p in pythonPlugins:
sys.path.append(p)
if isinstance(QgsApplication.instance(), QgsApplication):
#alread started
return QgsApplication.instance()
else:
if PATH_QGIS is None:
# find QGIS Path
if sys.platform == 'darwin':
#search for the QGIS.app
import qgis, re
assert '.app' in qgis.__file__, 'Can not locate path of QGIS.app'
PATH_QGIS_APP = re.split('\.app[\/]', qgis.__file__)[0]+ '.app'
PATH_QGIS = os.path.join(PATH_QGIS_APP, *['Contents','MacOS'])
if not 'GDAL_DATA' in os.environ.keys():
os.environ['GDAL_DATA'] = r'/Library/Frameworks/GDAL.framework/Versions/2.1/Resources/gdal'
QApplication.addLibraryPath(os.path.join(PATH_QGIS_APP, *['Contents', 'PlugIns']))
QApplication.addLibraryPath(os.path.join(PATH_QGIS_APP, *['Contents', 'PlugIns','qgis']))
else:
# assume OSGeo4W startup
PATH_QGIS = os.environ['QGIS_PREFIX_PATH']
assert os.path.exists(PATH_QGIS)
QgsApplication.setGraphicsSystem("raster")
qgsApp = QgsApplication([], True)
qgsApp.setPrefixPath(PATH_QGIS, True)
qgsApp.initQgis()
return qgsApp
if __name__ == '__main__':
#nice predecessors
from timeseriesviewer.sandbox import initQgisEnvironment
qgsApp = initQgisApplication()
se = SpatialExtent.world()
assert nicePredecessor(26) == 25
assert nicePredecessor(25) == 25
assert nicePredecessor(23) == 20
assert nicePredecessor(999) == 950
assert nicePredecessor(1001) == 1000
assert nicePredecessor(1.2) == 1.0 #
assert nicePredecessor(0.8) == 0.5
assert nicePredecessor(0.2) == 0.1
assert nicePredecessor(0.021) == 0.01
assert nicePredecessor(0.0009991) == 0.0005