/*
* Copyright (C) 2014 Jan Seibert (jan.seibert@geo.uzh.ch) and
* Marc Vis (marc.vis@geo.uzh.ch)
*
* 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 <http://www.gnu.org/licenses/>.
*/
package plugins;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import whitebox.geospatialfiles.WhiteboxRaster;
import whitebox.geospatialfiles.WhiteboxRasterBase;
import whitebox.interfaces.WhiteboxPlugin;
import whitebox.interfaces.WhiteboxPluginHost;
/**
* This tool removes creek sinks by digging a flowpath to a lower located cell.
* @author Dr. John Lindsay email: jlindsay@uoguelph.ca
*/
public class Digging implements WhiteboxPlugin {
private WhiteboxPluginHost myHost = null;
private String[] args;
double pi = Math.PI;
WhiteboxRaster dem;
WhiteboxRaster streamHeads;
WhiteboxRaster elevationModified;
WhiteboxRaster correctedDEM;
int numRows;
int numCols;
double maxRadius;
double fpStartElevation;
double fpMaxBetween;
int fpStartX;
int fpStartY;
int fpLength;
Date fpStartTime;
long fpMaxTime = 15000;
double fpLowerFactor = 0.001;
int[] xd = new int[]{0, -1, -1, -1, 0, 1, 1, 1};
int[] yd = new int[]{-1, -1, 0, 1, 1, 1, 0, -1};
double[] dd = new double[]{1, Math.sqrt(2), 1, Math.sqrt(2), 1, Math.sqrt(2), 1, Math.sqrt(2)};
int depth = 0;
double noData;
double gridRes = 1;
boolean blnDebug = false;
public class FlowPath {
private String mPath;
private double mLowerSum;
private double mFinalElevation;
private int mFinalX;
private int mFinalY;
public FlowPath(String path, double lowerSum, double finalElevation, int finalX, int finalY) {
mPath = path;
mFinalElevation = finalElevation;
mLowerSum = lowerSum;
mFinalX = finalX;
mFinalY = finalY;
}
public String GetPath() {
return mPath;
}
public double GetLowerSum() {
return mLowerSum;
}
public double GetFinalElevation() {
return mFinalElevation;
}
public int GetFinalX() {
return mFinalX;
}
public int GetFinalY() {
return mFinalY;
}
}
public class Neighbour implements Comparable<Neighbour> {
private int mDirection;
private double mGradient;
public Neighbour(int direction, double gradient) {
mDirection = direction;
mGradient = gradient;
}
public int GetDirection() {
return mDirection;
}
public double GetGradient() {
return mGradient;
}
@Override
public int compareTo(Neighbour o) {
double diff = this.GetGradient() - o.GetGradient();
if (diff > 0) {
return 1;
} else if (diff < 0) {
return -1;
} else {
return 0;
}
}
}
public class StreamHead implements Comparable<StreamHead>{
int mXCoord;
int mYCoord;
double mElevation;
public StreamHead(int x, int y, double elevation) {
mXCoord = x;
mYCoord = y;
mElevation = elevation;
}
public int GetXCoord() {
return mXCoord;
}
public int GetYCoord() {
return mYCoord;
}
public double GetElevation() {
return mElevation;
}
@Override
public int compareTo(StreamHead o) {
double diff = this.GetElevation() - o.GetElevation();
if (diff > 0) {
return 1;
} else if (diff < 0) {
return -1;
} else {
return 0;
}
}
}
/**
* Used to retrieve the plugin tool's name. This is a short, unique name containing no spaces.
* @return String containing plugin name.
*/
@Override
public String getName() {
return "Digging";
}
/**
* Used to retrieve the plugin tool's descriptive name. This can be a longer name (containing spaces) and is used in the interface to list the tool.
* @return String containing the plugin descriptive name.
*/
@Override
public String getDescriptiveName() {
return "Remove Creek Sinks (Digging)";
}
/**
* Used to retrieve a short description of what the plugin tool does.
* @return String containing the plugin's description.
*/
@Override
public String getToolDescription() {
return "Removes creek sinks by digging a flowpath to a lower located cell.";
}
/**
* Used to identify which toolboxes this plugin tool should be listed in.
* @return Array of Strings.
*/
@Override
public String[] getToolbox() {
String[] ret = { "FlowpathTAs" };
return ret;
}
/**
* Sets the WhiteboxPluginHost to which the plugin tool is tied. This is the class
* that the plugin will send all feedback messages, progress updates, and return objects.
* @param host The WhiteboxPluginHost that called the plugin tool.
*/
@Override
public void setPluginHost(WhiteboxPluginHost host) {
myHost = host;
}
/**
* Used to communicate feedback pop-up messages between a plugin tool and the main Whitebox user-interface.
* @param feedback String containing the text to display.
*/
private void showFeedback(String message) {
if (myHost != null) {
myHost.showFeedback(message);
} else {
System.out.println(message);
}
}
/**
* Used to communicate a return object from a plugin tool to the main Whitebox user-interface.
* @return Object, such as an output WhiteboxRaster.
*/
private void returnData(Object ret) {
if (myHost != null) {
myHost.returnData(ret);
}
}
private int previousProgress = 0;
private String previousProgressLabel = "";
/**
* Used to communicate a progress update between a plugin tool and the main Whitebox user interface.
* @param progressLabel A String to use for the progress label.
* @param progress Float containing the progress value (between 0 and 100).
*/
private void updateProgress(String progressLabel, int progress) {
if (myHost != null && ((progress != previousProgress) ||
(!progressLabel.equals(previousProgressLabel)))) {
myHost.updateProgress(progressLabel, progress);
}
previousProgress = progress;
previousProgressLabel = progressLabel;
}
/**
* Used to communicate a progress update between a plugin tool and the main Whitebox user interface.
* @param progress Float containing the progress value (between 0 and 100).
*/
private void updateProgress(int progress) {
if (myHost != null && progress != previousProgress) {
myHost.updateProgress(progress);
}
previousProgress = progress;
}
/**
* Sets the arguments (parameters) used by the plugin.
* @param args An array of string arguments.
*/
@Override
public void setArgs(String[] args) {
this.args = args.clone();
}
private boolean cancelOp = false;
/**
* Used to communicate a cancel operation from the Whitebox GUI.
* @param cancel Set to true if the plugin should be canceled.
*/
@Override
public void setCancelOp(boolean cancel) {
cancelOp = cancel;
}
private void cancelOperation() {
showFeedback("Operation cancelled.");
updateProgress("Progress: ", 0);
}
private boolean amIActive = false;
/**
* Used by the Whitebox GUI to tell if this plugin is still running.
* @return a boolean describing whether or not the plugin is actively being used.
*/
@Override
public boolean isActive() {
return amIActive;
}
/**
* Used to execute this plugin tool.
*/
@Override
public void run() {
amIActive = true;
String demHeader = null;
String streamHeadsHeader = null;
String elevationModifiedHeader = null;
String correctedDemHeader = null;
List<StreamHead> streamHeadList = new ArrayList<>();
int counter = 0;
float progress = 0;
if (args.length <= 0) {
showFeedback("Plugin parameters have not been set.");
return;
}
for (int i = 0; i < args.length; i++) {
if (i == 0) {
demHeader = args[i];
} else if (i == 1) {
streamHeadsHeader = args[i];
} else if (i == 2) {
elevationModifiedHeader = args[i];
} else if (i == 3) {
correctedDemHeader = args[i];
} else if (i == 4) {
maxRadius = Double.parseDouble(args[i]);
}
}
// check to see that the inputHeader and outputHeader are not null.
if ((demHeader == null) || (streamHeadsHeader == null) || (elevationModifiedHeader == null) || (correctedDemHeader == null)) {
showFeedback("One or more of the input parameters have not been set properly.");
return;
}
try {
dem = new WhiteboxRaster(demHeader, "r");
streamHeads = new WhiteboxRaster(streamHeadsHeader, "r");
numRows = dem.getNumberRows();
numCols = dem.getNumberColumns();
noData = dem.getNoDataValue();
gridRes = dem.getCellSizeX();
elevationModified = new WhiteboxRaster(elevationModifiedHeader, "rw", demHeader, WhiteboxRaster.DataType.FLOAT, 0);
elevationModified.setPreferredPalette("blueyellow.pal");
elevationModified.setDataScale(WhiteboxRasterBase.DataScale.CONTINUOUS);
elevationModified.setZUnits("dimensionless");
correctedDEM = new WhiteboxRaster(correctedDemHeader, "rw", demHeader, WhiteboxRaster.DataType.FLOAT, 0);
correctedDEM.setPreferredPalette("blueyellow.pal");
correctedDEM.setDataScale(WhiteboxRasterBase.DataScale.CONTINUOUS);
correctedDEM.setZUnits("dimensionless");
if (streamHeads.getNumberColumns() != numCols || streamHeads.getNumberRows() != numRows) {
showFeedback("Input images must have the same dimensions.");
return;
}
// Initialize grids
updateProgress("Loop 1 of 4:", 0);
for (int row = 0; row < numRows; row++) {
for (int col = 0; col < numCols; col++) {
if (dem.getValue(row, col) != noData) {
elevationModified.setValue(row, col, 0);
} else {
elevationModified.setValue(row, col, noData);
}
}
if (cancelOp) {
cancelOperation();
return;
}
progress = (float) (100f * row / (numRows - 1));
updateProgress("Loop 1 of 4:", (int) progress);
}
// Loop through all cells
updateProgress("Loop 2 of 4:", 0);
for (int row = 0; row < numRows; row++) {
for (int col = 0; col < numCols; col++) {
// If the current cell is a stream head
if (streamHeads.getValue(row, col) == 1) {
streamHeadList.add(new StreamHead(col, row, dem.getValue(row, col)));
}
}
if (cancelOp) {
cancelOperation();
return;
}
progress = (float) (100f * row / (numRows - 1));
updateProgress("Loop 2 of 4:", (int) progress);
}
streamHeadList = OrderStreamHeads(streamHeadList);
updateProgress("Loop 3 of 4:", 0);
for (StreamHead streamHead : streamHeadList) {
CheckFlowPath(streamHead.GetXCoord(), streamHead.GetYCoord());
counter = counter + 1;
if (cancelOp) {
cancelOperation();
return;
}
progress = (float) (100f * counter / streamHeadList.size());
updateProgress("Loop 3 of 4:", (int) progress);
}
// Generate the output DEM
updateProgress("Loop 4 of 4:", 0);
for (int row = 0; row < numRows; row++) {
for (int col = 0; col < numCols; col++) {
if (elevationModified.getValue(row, col) != noData) {
correctedDEM.setValue(row, col, dem.getValue(row, col) - elevationModified.getValue(row, col));
} else {
correctedDEM.setValue(row, col, noData);
}
}
if (cancelOp) {
cancelOperation();
return;
}
progress = (float) (100f * row / (numRows - 1));
updateProgress("Loop 4 of 4:", (int) progress);
}
elevationModified.addMetadataEntry("Created by the " + getDescriptiveName() + " tool.");
elevationModified.addMetadataEntry("Created on " + new Date());
correctedDEM.addMetadataEntry("Created by the " + getDescriptiveName() + " tool.");
correctedDEM.addMetadataEntry("Created on " + new Date());
dem.close();
streamHeads.close();
elevationModified.close();
correctedDEM.close();
// returning a header file string displays the image.
returnData(correctedDemHeader);
} catch (Exception e) {
showFeedback(e.getMessage());
} finally {
updateProgress("Progress: ", 0);
// tells the main application that this process is completed.
amIActive = false;
myHost.pluginComplete();
}
}
private double CorrectedElevation(int x, int y) {
double elevation = dem.getValue(y, x);
double correction = elevationModified.getValue(y, x);
if (elevation != noData && correction != noData) {
return (elevation - correction);
} else {
return noData;
}
}
private void CheckFlowPath(int col, int row) {
int x, y;
double z, z2;
boolean flag;
// D8 variables
double slope;
double maxSlope;
double maxFlowDir;
int c;
// Radius search variables
boolean downslope;
int radius;
double routeDistance;
double routeDepth;
double routeVolume;
double minRouteVolume;
int routeToX = 0;
int routeToY = 0;
// Digging variables
int flowDistance;
double elevationDifference;
int x1, x2, y1, y2;
double lowerSum;
String directPath;
double finalElevation;
int d = 0;
int xn, yn;
int direction;
double deltaElevation;
FlowPath flowPath;
try {
z = CorrectedElevation(col, row);
maxSlope = Double.MIN_VALUE;
maxFlowDir = 255;
flag = false;
if (z != noData) {
// ------------- //
// D8 algorithm
// ------------- //
// Find the neighbour with the steepest slope (and lower elevation)
for (c = 0; c < 8; c++) {
x = col + xd[c];
y = row + yd[c];
z2 = CorrectedElevation(x, y);
if (z > z2 && z2 != noData) {
slope = (z - z2) / dd[c];
if (slope > maxSlope) {
maxSlope = slope;
maxFlowDir = c;
}
}
}
// Call this function recursively for the steepest slope neighbour
for (c = 0; c < 8; c++) {
if (c == maxFlowDir) {
x = col + xd[c];
y = row + yd[c];
flag = true;
CheckFlowPath(x, y);
}
}
// ------------- //
// Radius search
// ------------- //
// If no neighbour with a lower elevation has been found, then start the 'radius search'
if (flag == false) {
// Initialize
radius = 0;
downslope = false;
minRouteVolume = Double.MAX_VALUE;
while (radius <= maxRadius & downslope == false) {
for (int i = -radius; i <= radius; i++) {
for (int j = -radius; j <= radius; j++) {
if (Math.abs(i) > radius - 1 | Math.abs(j) > radius - 1) {
x = col + i;
y = row + j;
z2 = CorrectedElevation(x, y);
if (z2 != noData && z2 < z) {
routeDistance = Math.sqrt(i * i + j * j) * gridRes;
routeDepth = AverageAlongLine(col, row, x, y);
if (routeDepth >= 0) {
routeVolume = routeDistance * routeDepth;
if (routeVolume < minRouteVolume) {
downslope = true;
minRouteVolume = routeVolume;
routeToX = x;
routeToY = y;
}
}
}
}
}
}
radius = radius + 1;
}
// ------------- //
// Digging
// ------------- //
if (minRouteVolume != Double.MAX_VALUE) {
// Initialize
lowerSum = 0;
fpMaxBetween = 0;
directPath = "";
x1 = col;
y1 = row;
x2 = col;
y2 = row;
flowDistance = Math.max(Math.abs(routeToX - col), Math.abs(routeToY - row));
// Get the direct path from (a,b) to (routeToX, routeToY)
for (int f = 1; f <= flowDistance; f++) {
// Get the direction of the next cell on the direct path
switch ((int)Math.signum(Math.abs(routeToX - x1) - Math.abs(routeToY - y1))) {
case 1:
x2 = x1 + (int)Math.signum(routeToX - x1);
if (routeToX > x1) {
d = 4;
} else {
d = 8;
}
break;
case 0:
x2 = x1 + (int)Math.signum(routeToX - x1);
y2 = y1 + (int)Math.signum(routeToY - y1);
if (routeToX > x1) {
if (routeToY > y1) {
d = 5;
} else {
d = 3;
}
} else {
if (routeToY > y1) {
d = 7;
} else {
d = 1;
}
}
break;
case -1:
y2 = y1 + (int)Math.signum(routeToY - y1);
if (routeToY > y1) {
d = 6;
} else {
d = 2;
}
break;
}
// Update the lowerSum and fpMaxBetween values
if (!(x2 == routeToX & y2 == routeToY)) {
z2 = CorrectedElevation(x2, y2);
if (z2 != noData) {
lowerSum = lowerSum + gridRes * fpLowerFactor + z2 - z;
if (z2 - z > fpMaxBetween) {
fpMaxBetween = z2 - z;
}
} else {
lowerSum = lowerSum + dem.getMaximumValue();
fpMaxBetween = z2 - z;
}
}
directPath = directPath + d;
x1 = x2;
y1 = y2;
}
// Get the elevation of the last cell of the flowPath
finalElevation = CorrectedElevation(routeToX, routeToY);
// Only if the direct path is going through a cell with an elevation difference of at least 0.5
if (fpMaxBetween > 0.5) {
fpStartElevation = z;
fpStartX = col;
fpStartY = row;
fpStartTime = new Date();
fpLength = directPath.length();
flowPath = FindFlowPath(col, row, 0, 0, 0, lowerSum);
if (flowPath == null) {
flowPath = new FlowPath(directPath, lowerSum, finalElevation, routeToX, routeToY);
}
} else {
flowPath = new FlowPath(directPath, lowerSum, finalElevation, routeToX, routeToY);
}
} else {
// Unable to remove sink
return;
}
// Loop through the flowpath and apply the modification to the elevmodified grid
xn = col;
yn = row;
flowDistance = flowPath.GetPath().length();
elevationDifference = z - flowPath.GetFinalElevation();
for (int f = 1; f <= flowDistance; f++) {
direction = Integer.parseInt(flowPath.GetPath().substring(f - 1, f));
xn = XNeighbour(xn, direction);
yn = YNeighbour(yn, direction);
deltaElevation = -(z - f * elevationDifference / flowDistance - dem.getValue(yn, xn));
if (deltaElevation > elevationModified.getValue(yn, xn)) {
elevationModified.setValue(yn, xn, deltaElevation);
} else {
break;
}
}
// Call this function for the last cell of the flowpath found so far
CheckFlowPath(flowPath.GetFinalX(), flowPath.GetFinalY());
}
}
} catch (Exception e) {
showFeedback(e.getMessage());
}
}
private FlowPath FindFlowPath(int x, int y, int directionBefore, int steps, double lowerSum, double lowerSumMin) {
double z;
double z2;
int h1;
int h2;
int xn;
int yn;
int i;
FlowPath flowpath = null;
FlowPath tmpFlowPath;
int direction;
double gradient;
List<Neighbour> neighbours;
String path;
double finalElevation;
try {
z = CorrectedElevation(x, y);
// If a larger volume needs to be digged then for the best route found so far, stop investigating the current path
if (lowerSum > lowerSumMin) {
return null;
}
if (steps > 1) {
// If the path deviates 'too much// from a straight line, then stop investigating the current path
if (steps / 2.5 > Math.max(Math.abs(fpStartX - x), Math.abs(fpStartY - y))) {
return null;
}
// If the computation takes 'too long', then stop investigating the current path
Date currentTime = new Date();
if (currentTime.getTime() - fpStartTime.getTime() > fpMaxTime) {
return null;
}
}
// Get the lower and upper directions between which a path should be searched for
if (directionBefore == 0) {
h1 = 1;
h2 = 8;
} else if (directionBefore % 2 == 0) {
h1 = directionBefore - 1;
h2 = directionBefore + 1;
} else {
h1 = directionBefore - 2;
h2 = directionBefore + 2;
}
// Initialize
neighbours = new ArrayList<>();
// For each direction between the lower and upper direction values
for (int ii = h1; ii <= h2; ii++) {
i = ii;
if (i > 8) {
i = i - 8;
}
if (i < 1) {
i = i + 8;
}
// Get the coordinates of the neighboor cell in direction i
xn = XNeighbour(x, i);
yn = YNeighbour(y, i);
z2 = CorrectedElevation(xn, yn);
// If the elevation value != noData
if (z2 != noData) {
// Increase the number of potential directions with 1 and store the corresponding direction and gradient
direction = i;
gradient = -(z - z2) / (gridRes * Math.sqrt(1 + (i % 2)));
neighbours.add(new Neighbour(direction, gradient));
}
}
if (neighbours.size() > 0) {
// Sort based on the gradient
neighbours = OrderNeighbours(neighbours);
// Get direction, x and y for the smallest gradient
i = neighbours.get(0).GetDirection();
xn = XNeighbour(x, i);
yn = YNeighbour(y, i);
z2 = CorrectedElevation(xn, yn);
// In case the elevation minus the modified elevation is smaller than the start elevation...
if (z2 < fpStartElevation) {
// ...we're finished!
path = Integer.toString(i);
finalElevation = z2;
flowpath = new FlowPath(path, lowerSum, finalElevation, xn, yn);
} else {
// For each of the directions
for (int ii = 0; ii < neighbours.size(); ii++) {
// Get the corresponding direction, x and y
i = neighbours.get(ii).GetDirection();
xn = XNeighbour(x, i);
yn = YNeighbour(y, i);
z2 = CorrectedElevation(xn, yn);
// In case the route is going via a higher point than the best route so far, then stop investigating the current path.
// (NOTE: All other directions will pass an even higher point, since values have been sorted based on the gradient)
if (z2 - fpStartElevation > fpMaxBetween) {
break;
}
// Call the currect method for the neighbor cell
tmpFlowPath = FindFlowPath(xn, yn, i, steps + 1, lowerSum + gridRes * fpLowerFactor + z2 - fpStartElevation, lowerSumMin);
// In case a flowpath has been found...
if (tmpFlowPath != null) {
if (tmpFlowPath.GetLowerSum() < lowerSumMin) {
lowerSumMin = tmpFlowPath.GetLowerSum();
flowpath = new FlowPath(i + tmpFlowPath.GetPath(), tmpFlowPath.GetLowerSum(), tmpFlowPath.GetFinalElevation(), 0, 0);
}
}
}
}
}
} catch (Exception e) {
showFeedback(e.getMessage());
}
return flowpath;
}
public List<Neighbour> OrderNeighbours(List<Neighbour> neighbours) {
Collections.sort(neighbours);
return neighbours;
}
public List<StreamHead> OrderStreamHeads(List<StreamHead> streamHeadList) {
Collections.sort(streamHeadList, Collections.reverseOrder());
return streamHeadList;
}
private int XNeighbour(int x, int direction) {
int d = -1;
try {
switch (direction) {
case 1: case 7: case 8:
d = x - 1;
break;
case 2: case 6:
d = x;
break;
case 3: case 4: case 5:
d = x + 1;
break;
}
if (d > numCols - 1 | d < 0) {
d = -1;
}
} catch (Exception e) {
showFeedback(e.getMessage());
}
return d;
}
private int YNeighbour(int y, int direction) {
int d = -1;
try {
switch (direction) {
case 1: case 2: case 3:
d = y - 1;
break;
case 4: case 8:
d = y;
break;
case 5: case 6: case 7:
d = y + 1;
break;
}
if (d > numRows - 1 | d < 0) {
d = -1;
}
} catch (Exception e) {
showFeedback(e.getMessage());
}
return d;
}
private double AverageAlongLine(int x1, int y1, int x2, int y2) {
double z2;
double baseLevel;
int xCurrent;
int yCurrent;
double zCurrent = 0;
int xNext;
double xCurrentValue;
double xNextValue;
double lineSlope;
double lineSum = 0;
int h;
int n = 0;
boolean down = false;
boolean first;
try {
baseLevel = CorrectedElevation(x1, y1);
// Switch points in case x1 > x2
if (x1 > x2) {
h = x1;
x1 = x2;
x2 = h;
h = y1;
y1 = y2;
y2 = h;
}
// If the line from (x1,y1) to (x2,y2) doesn't have an infinite slope
if (x1 != x2) {
// Initialize
lineSum = 0;
n = 0;
first = true;
lineSlope = (y1 - y2) / (double) (x1 - x2);
xCurrent = x1;
yCurrent = y1;
xCurrentValue = x1 + 0.5;
do {
// Get the x-coordinate of the next cell on the line
if (first) {
first = false;
if (lineSlope != 0) { // i.e. if not y1 = y2
xNextValue = Math.min(xCurrentValue + (0.5 / Math.abs(lineSlope)), numCols);
} else {
// Since the distance between two adjacent gridcells on the line is exactly 1, the computation to the endpoint x2 can be done in one iteration
xNextValue = x2;
}
} else {
xNextValue = Math.min(xCurrentValue + (1 / Math.abs(lineSlope)), numCols);
}
// Make sure the endpoint of the line will not be passed
xNext = Math.min(x2, (int)(xNextValue));
// Correction needed in case the slope is exactly 1
if (Math.abs(lineSlope) == 1) {
xNext = xNext - 1;
}
// Move in the x-direction from xCurrent to xNext
for (int i = xCurrent; i <= xNext; i++) {
z2 = CorrectedElevation(i, yCurrent);
if (z2 != noData) {
// Get the maximum of the elevation of cell (x1, y1) and (i, yCurrent)
zCurrent = Math.max(baseLevel, z2);
}
// If the elevation of the current cell is equal or higher then the elevation of the starting point of the line...
if (zCurrent >= baseLevel) {
// ...add the difference to the lineSum
lineSum = lineSum + zCurrent - baseLevel;
n = n + 1;
} else if (! ((x1 == i & y1 == yCurrent) | (x2 == i & y2 == yCurrent))) { // If the current cell is not the start or end point of the line
down = true;
}
}
if (lineSlope > 0) { // i.e. if y1 < y2
yCurrent = yCurrent + 1;
if (yCurrent > numRows - 1) {
yCurrent = numRows - 1;
}
} else if (lineSlope < 0) {
yCurrent = yCurrent - 1;
if (yCurrent < 0) {
yCurrent = 0;
}
}
// Correction needed in case the slope is exactly 1
if (Math.abs(lineSlope) == 1) {
xNext = xNext + 1;
}
// Update xCurrent and xCurrentValue
xCurrent = xNext;
xCurrentValue = xNextValue;
} while (!(xCurrent >= x2 & (lineSlope == 0 | (lineSlope > 0 & yCurrent >= y2) | (lineSlope < 0 & yCurrent <= y2)))); // Loop until the end of the line is passed
} else {
// Loop from one to the other endpoint of the line
for (int j = Math.min(y1, y2); j <= Math.max(y1, y2); j++) {
z2 = CorrectedElevation(x1, j); // NOTE: since x1 = x2, they can be used interchangeably
if (z2 != noData) {
zCurrent = z2;
}
// If the elevation of the current cell is equal or higher then the elevation of the starting point of the line...
if (zCurrent >= baseLevel) {
// ...add the difference to the lineSum
lineSum = lineSum + zCurrent - baseLevel;
n = n + 1;
} else if (! ((x1 == x2 & y1 == j) | (x2 == x1 & y2 == j))) { // Remark: partly redundant, since x1 = x2...!?!
down = true;
}
}
}
} catch (Exception e) {
showFeedback(e.getMessage());
}
// If the line between (x1,y1) and (x2,y2) is passing at least one cell with a higher elevation then the starting point AND there are no cells with a lower elevation
if (n > 0 & ! down) {
return lineSum / n;
} else {
return -1;
}
}
}