Point-To-Point Caliper Module

The Point-To-Point Caliper module allows to take point to point measurements on the current image.

To get the distance between two points, provided the module was calibrated beforehand, the user simply do a click and drag (left mouse button) from a start point to and end point. The module will draw a line between the two points and the measured value will be shown. The measurement line will stay visible until it is redrawn by doing a new click-drag action or removed by clicking without dragging or by pressing the [Clear] button.

"Measure" tab

The "Draw Overlays" section is used to determine when the overlay burning is taking place.

When done "At grab level", the overlays will be written on the images as soon as they are received from the camera. "On displayed frames" will show the overlays on images received from the camera but after any saving process occured. It will also show overlays on images read from a sequence file. Finally, "On exported frames" will apply overlay to any images exported from a sequence, regardless of the destination format (seq, avi, bmp, jpg, etc).

Checking the "Lock Overlay" checkbox will make the module ignore mouse clicks and actions.

In the Units edit box, type the abreviation used for the measurements. It can be : pixels, mm, m, cm, km, %, or anything else.

In the precision box, type the number of digits to show after the point in measurements.

[Clear] will erase the current measurement line.

"Calibrate" tab

While the "Calibrate" tab is the active tab, the module is in calibration mode. Quit calibration mode by selecting any another tab. Calibration mode, to set reference values. The measurement line will use those reference values to compute its real length.

To calibrate, first select one of the 3 calibration methods available. Any measurements will be done using the currently selected calibration method. Here is how to proceed for each.

  • Inter-Pixel: The simplest method. This method assume the client knows the exact distance between each pixel of the image. To calibrate, type the distance in the "Calibrated length" and click on [Set]. The current calibrated length appears as an overlay at the bottom of the image.
  • Between 2 points: The standard method. This method require the user to click and drag a line on the image. Once the line is drawn, the user can enter the line's length in "Calibrated length" and click on [Set]. Be careful, if you redraw or remove the calibration line, you have to modify the "Calibrated length" accordingly.
  • Between 2 points (H & V) : The advanced method. This method is only used for cameras that don't have square pixels, i.e. the inter-cells distance on the CCD is not the same horizontally and vertically. The calibration procedure is the same as the previous method (between 2 points) except that the user has to make 2 calibration : a horizontal one and a vertical one. Both MUST be done for the measurements to work correctly. The horizontal calibration is done by drawing an horizontal line and entering its length. The vertical calibration is done with a vertical line.
  • When the calibration is completed, click on the "Measure" tab and do a couple of test measurement lines to see if everything is correctly calibrated. If not, return to the "Calibrate" tab and readjust the calibration.

"Overlay Settings" tab

This tab control how the various overlays are drawn.

  • Line: Affect the how the measurement lines are drawn. Select either a "simple line" or a "Flat ends line". Flat ends lines are the default.
  • InfoText: This text displays the length of the current measurement line. You can set its position to any corner of the image. You can also choose a suitable font and the font size. For best results, use fixed width fonts such as Terminal or Courier.
  • Colors : Here, you can change the color of the measurement line (default is pink). You can also change the color of the text overlays (default is white on black). If the text background color is the same as the text color, no background color will be used resulting in a transparent background.
  • Scale: Type the length of the scale (in current "Units"). You can also set the position of the scale and its orientation (horizontal or vertical). To hide the scale, select "None" from the "Position" drop-down list.