Pointy: A tool for editing matched points on images

Pointy is somewhat limited, and it would be ideal to rewrite it in QT, or Java, or just about anything else besides TCL, but I never find the time. Despite its limitations it has proved pretty useful, and I hope you find it useful too. Please send bug reports, or ideally bug fixes, comments, etc to rupert at rupertbrooks dot ca.

Obtaining Pointy

License

• You may freely modify, use and distribute the software, but
• such modifications must be open sourced, and clearly identified.
• However, you may combine the software with other work, in which case only this software must be kept open source, but the other work can be licensed however you wish.
• There is no warranty.

Installation and Usage

1. Linux:
The shebang line at the top of the script should enable your shell to associate the Tcl/Tk interpreter (wish) with pointy. Then pointy.tcl should be placed in your path, and may be started at the command line by typing

      pointy.tcl

2. Windows:
If a system such as Active Tcl is installed, files with the .tcl extension may be associated with the TclTk interpreter, and may be made executable by adding .tcl to the PATHEXT environment variable. Then pointy.tcl may be placed in your path and started from the command line as above.
3. Cygwin and Active TCL:
Only try this approach if the previous two approaches don't work for you. On my own system, I have both cygwin and activeTCL installed, and I prefer to run pointy from the cygwin bash prompt with the activeTCL interpreter rather than the cygwin one. This can only be achieved by taking the cygwin paths OUT of the system path before starting pointy. I achieve this using a small bash script called pointy which contains the following.

      #!/bin/bash
      SCRIPTPATHWIN=$(cygpath -m "$(which pointy.tcl)" )
      export PATH=`stripout.pl PATH '^/usr' '^/bin'`
      #echo "$SCRIPTPATHWIN"
      wish "$SCRIPTPATHWIN" $*

stripout.pl is a perl script containing the following.

      #!perl
      $var=$ENV{$ARGV[0]};
      @vararray=split(/:/,$var);
      for($i=1;$i<=$#ARGV;$i++) {
          for($j=0;$j<$#vararray;$j++) {
             if($vararray[$j]=~/$ARGV[$i]/) {
                # drop this item from the list
                #print "Dropping $vararray[$j]\n";
                splice(@vararray,$j,1);
                #print "$j now $vararray[$j]\n";
                $j--;
             }
          }
      }
      print join(":",@vararray),"\n";

This type of approach may work for you if you have multiple installations of things that interfere with each other.

4. Last resort:
You can also always call the TclTk interpreter and pass the pointy script as an argument. For example

      wish [path/to/pointy/pointy.tcl] {arguments....}

      pointy leftimage rightimage

Starting pointy in this way brings up the interface with the left image on the left, and the right image on the right. Which brings us to...

Using Pointy

Overview

• Add a point. Left Click
• Move a point. Left Click and drag
• Change size and orientation of surround. Right Click and drag.
• Change eccentricity of ellipse. Center-click and drag.
• Delete a point. While mouse is over it, press "delete".

Examples

Example 1: Hong Kong: Adding simple point matches.

      C:\home\development\pointy\Examples>pointy hongkong/hk1a.png hongkong/hk2a.png

This should pop up the pointy window, with both images at least partly shown.

Example 2: Hong Kong: Adding simple point matches.

Once you have added more points to your satisfaction, on the file menu select "Save Plain matches" to save them to a text file.

Matched points frequently have more information on the matched region than just the center point. Pointy allows you to edit the oriented ellipse that surrounds each point. Right-clicking and dragging changes the size and orientation of the surrounding region. You can stretch the point into an ellipse using the middle button and dragging.. If you save the point as an affine point the ellipse information is kept. If you save it as a sift point, only the size and orientation (ie, an oriented circle) is kept. Finally if you save it as a plain point, only the centroid is kept.

Example 3: Hong Kong: Viewing a homography.

Example 4: Shed: Sift keypoints

      pointy shed\img_1596.pgm shed\img_1597.pgm

Now go to the file menu, select "Load Sift points" and navigate to the shed/img_1596_1597.sift file. You should see many points with circles of different sizes and different orientations. Move your mouse over a particular circle to highlight the matched pair in each image.

Example 5: Shed: Viewing epipolar lines

Known bugs and todo list

• Does not support magnification or scaling of the images. This is because the canvas widget does not (easily) support magification or scaling.
• Currently does not allow loading images from the menu. They must be specified on the command line.
• Currently saving affine points is not implemented