Michael Thomas Flanagan's Java Scientific Library: Digitizing graph points

Michael Thomas Flanagan's Java Scientific Library

DigiGraph Class: Digitizing Points on a Graph

Last update: 3 December 2008 Main Page of Michael Thomas Flanagan's Java Scientific Library

This class contains the methods for digitizing points on a graph. The graph must be presented in one of the following graphical formats:

GIF	[Graphical Interchange Format]	(.gif, .GIF)
JPEG	[Joint Photographic Experts Group]	(.jpg, .JPG, .jpeg, .JPEG, .jpe, .JPE, .jfif, JFIF)
PNG	[Portable Network Graphics]	(.png, .PNG)

Summary table of constructor and methods
Details of constructor and methods
A simple application calling DigiGraph
Listing of the source code, DigiGraph.java (Last update: 3 December 2008)
Other classes, in this library, used by this class
Main Page of Michael Thomas Flanagan Java Scientific Library

SUMMARY OF CONSTRUCTOR AND METHODS

Constructors	public DigiGraph() public DigiGraph(String windowPath)
Digitize points on the graph	public void digitize() public void digitise()
Reset window height	public void setWindowHeight(int height)
Reset window width	public void setWindowWidth(int width)
Reset window closing option	public void setCloseChoice(int option)
Reset axes rotation tolerance	public void setRotationTolerance(double tol)
Block digitised data plot	public void noPlot()
Retain identical points	public void keepIdenticalPoints()
End the program	public static final synchronized void.endProgram()
End the program	System.exit(0)

CONSTRUCTORS AND METHODS

CONSTRUCTORS
public DigiGraph()
public DigiGraph(String windowPath)
Usage: DigiGraph dg = new DigiGraph();
Creates a new instance of DigiGraph. A file selection window will appear, if this constructor is used, allowing the user to select the GIF, JPEG or PNG file containing the graph to be digitized. The window will open on your system's default initial directory.

On selecting the required GIF, JPEG or PNG file a dialog box will appear requesting the path\name of the output .txt file. The default path for the output file is to the directory in which the selected image file is stored and the default name is the name of the selected file with"_digitized" added. The path name must conform to the convention of the operating system, e.g. if a Microsoft System is being used, an example would be "C:\\Digitization\\Image_Files\\imageOne_digitized.txt". The output file will be stored in the same directory as the calling program if a name is entered without a directory path, e.g."imageOne_digitized.txt".

On entering an output file name a new dialog box will open requesting the number of decimal places required in the digitised values in the output file. The default option is 16.

On entering the required number of decimal places the selected image will be displayed in a new window. It may open as a minimized icon bar in the top left hand corner of the screen

If so click on the maximize icon (square icon second from the right) to restore a full window displaying the selected image.
The digitization of points on the image require the method digitize() to be called (see below).

Usage: DigiGraph dg = new DigiGraph(windowPath);
Creates a new instance of DigiGraph. A file selection window will appear, if this constructor is used, allowing the user to select the GIF, JPEG or PNG file containing the graph to be digitized. The window will open in the directory provided by the argument windowPath. The path name must conform to the convention of the operating system, e.g. if a Microsoft System is being used, an example would be "C:\\Digitization\\Image_Files"
On selecting the required GIF, JPEG or PNG file a dialog box will appear requesting the path\name of the output .txt file. The default path for the output file is to the directory in which the selected image file is stored and the default name is the name of the selected file with"_digitized" added. The path name must conform to the convention of the operating system, e.g. if a Microsoft System is being used, an example would be "C:\\Digitization\\Image_Files\\imageOne_digitized.txt". The output file will be stored in the same directory as the calling program if a name is entered without a directory path, e.g."imageOne_digitized.txt".

On entering an output file name a new dialog box will open requesting the number of decimal places required in the digitised values in the output file. The default option is 16.

On entering the required number of decimal places the selected image will be displayed in a new window. It may open as a minimized icon bar in the top left hand corner of the screen

DIGITIZE
public void digitize()
public void digitise()
The methods digitize and digitise are identical.
Usage: dg.digitize();
This method allows the points on a graph to be digitised. The GIF, JPEG or PNG file, containing the graph, supplied via the constructor initiated select window or constructor argument, is displayed in a window. Throghout the digitization the current digitization instruction is displayed above the selected image. To digitize points:

Click on four calibration points [calibration point required is indicated at the top left of the window]:
- Place cursor pointer on a known low value on the y-axis (ordinate axis, vertical axis) [typically the origin if value known]
- click RIGHT mouse or touch pad button [cross wire symbol will appear on successful click, will disappear on clicking on next point]
- A dialog box will appear requesting the value of the chosen lower y-axis (ordinate axis) calibration point
- Enter value and click on OK [moves program on to next calibration point]
- Place cursor pointer on a known high value on the y-axis (ordinate axis) [typically the highest ticked known value]
- click RIGHT mouse or touch pad button [cross wire symbol will appear on successful click, will disappear on clicking on next point]
- A dialog box will appear requesting the value of the chosen higher y-axis (ordinate axis) calibration point
- Enter value and click on OK [moves program on to next calibration point]
- Place cursor pointer on a known low value on the x-axis (abscissa axis, horizontal axis) [typically the origin if value known]
- click RIGHT mouse or touch pad button [cross wire symbol will appear on successful click, will disappear on clicking on next point]
- A dialog box will appear requesting the value of the chosen lower x-axis (abscissa axis) calibration point
- Enter value and click on OK [moves program on to next calibration point]
- Place cursor pointer on a known high value on the x-axis (abscissa axis) [typically the highest ticked known value]
- click RIGHT mouse or touch pad button [cross wire symbol will appear on successful click, will disappear on clicking on next point]
- A dialog box will appear requesting the value of the chosen higher x-axis (abscissa axis) calibration point
- Enter value and click on OK [moves program on to data point digitization]
Click on the data points to be digitized:
- Place cursor pointer on first data point to be digitized
- click LEFT mouse or touch pad button [cross wire symbol will appear on successful click, will disappear on clicking on next point]
- REPEAT for all data points to be digitized
- click RIGHT mouse or touch pad button when ALL data points have been digitized [moves program on to interpolation option request]
Choose to add a cubic spline interpolation:
- A dialog box will appear asking whether you wish, additionally, to perform a cubic spline interpolation on the digitized data
- Click on YES or NO [press return for the default option which is NO]
- If you requested the interpolation [YES answer above]
  - A dialog box will appear requesting the number of interpolation points required [default value is 200]
  - Enter the value and click on OK [simply click on OK for the default value]
OUTPUT FILE - the output file is a .txt file with tabulation so that it may also be read usefully, e.g. by Microsoft Excel. The file lists:
- The program title
- The output file name and the time and date of the file's creation
- The name of the image file used
- The location of the image file used
- The clockwise angle by which the y-axis (ordinate axis) deviates from the vertical
- The clockwise angle by which the x-axis (abscissa axis) deviates from the horizontal
- The mean of the above two angles
- A statement as to whether the data was rotated to give normal coordinate axes [see Rotation angle tolerance below]
- The number of digitized points
- A tabulated table of the pairs of digitized x values (abscissa values) and y values (ordinate values)
- If the interpolation option was chosen:
  - The number of interpolation points
  - A tabulated table of the pairs of interpolated x values (abscissa values) and y values (ordinate values)
The destination of the output file is entered in the response to the request for the output file name. See Constructors for details

Usage: dg.digitise();
The methods digitise and digitize (see immediately above) are identical.

SELECT WINDOW DIRECTORY PATH
Reset the path to the initially displayed directory
public void setPath(String path)
Usage: dg.setPath(path);
This method allows the path to the directory displayed in the select file box to be reset. The format of the path String must conform to the convention of the operating system, e.g. if a Microsoft System is being used, an example of path would be "C:\\Java_Programming\\Digitization\\Image_Files".

RESET THE HEIGHT OF THE GRAPH WINDOW
public void setWindowHeight(int height)
Usage: dg.setWindowHeight(height);
Resets the height, in pixels, of the graph window. Overwrites the preset value which is your computer's screen height - 40 pixels.

RESET THE WIDTH OF THE GRAPH WINDOW
public void setWindowWidth(int width)
Usage: dg.setWindowWidth(width);
Resets the width, in pixels, of the graph window. Overwrites the preset value which is your computer's screen width - 30 pixels.

RESET THE WINDOW CLOSING OPTION
public void setCloseChoice(int closeChoice)
Usage: pg.setCloseChoice(closechoice);
Resets the window closing option:

If closeChoice = 1 clicking on the graph window close icon (x cross box in the top right hand corner) closes the window and the program is exited. This is the default option if this method is not called.
If closeChoice = 2 clicking on the graph window close icon closes the window but leaves the program running. Overwrites the preset value of 1.

RESET THE AXES ROTATION ANGLE TOLERANCE
public void setRotationTolerance(double tolerance)
Usage: dg.setRotationTolerance(tolerance);
If the ordinate (y) and abscissa (x) axes are not coincident with the vertical and horizontal both the axes and the data are rotated to bring the axes in line with the vertical and horizontal. This rotation is applied if the mean angle of divergence of the x and y axis from the horizontal and vertical respectively is greater than a set tolerance. The preset value of the tolerance is zero degrees, i.e. the axes are rotated if the axes are not coincident with vertical and horizontal. This method allows this preset tolerance to be replaced by the user's value, in degrees, through this method's argument tolerance.

BLOCK THE DIGITIZED DATA AND THE INTERPOLATED DATA PLOTS
public void noPlot()
Usage: dg.noPlot();
A plot of the digitized data is automatically displayed and, if the interpolation option (see digitize above) has been chosen, this plot will also display the interpolated data. Calling this method, noPlot(), blocks this plot from being displayed.

RETAIN ALL IDENTICAL POINTS
public void keepIdenticalPoints()
Usage: dg.keepIdenticalPoints();
The default option of this class is to search for identical digitized points and remove all but one instance of each set of identical points as these usually arise from accidently clicking the mouse more than once while sat on a point. Calling this method causes this check to be skipped and all identical points are retained..

ENDING AN APPLICATION THAT USES DigiGraph
public void endProgram()
Usage:
dg.endProgram();
This method displays a dialogue box that asks if you want to end the program. Answering yes ends the program. Answering no displays a message telling you how you may now end the program. Ending the program also closes the graph window.

Any application that you write that displays a graphical user interface, as the digitize method in this class, DigiGraph, does, must be terminated:

with the line System.exit(0);
or by calling a method that contains that statement, e.g. by calling endProgram()
or, in the special case of DigiGraph, by closing the graph window if window closing option (see setCloseChoice above) is set at 1, i.e. at the default option.

Options 2 or 3 are recommended in the case of applications using DigiGraph.

EXAMPLE APPLICATION

RunDigiGraph is a simple application calling DigiGraph. Users must provide their own image files

Listing of the source code, RunDigiGraph.java

OTHER CLASSES USED BY THIS CLASS

This class uses the following classes in this library:

This page was prepared by Dr Michael Thomas Flanagan