3.0 Image Analysis Tools

3.1 Cursor

The cursor function displays line/sample values in both image and file coordinates and displays a matrix of gray level values surrounding the point of interest. Optionally, the user may choose to display:

  1. Projection coordinates
  2. Latitude/longitude coordinates
  3. Unscaled gray level values
This information may be calculated for any displayed image window (e.g., main image window, full resolution image window, zoom image window, etc.) by using the mouse to move the cursor into the appropriate window. Single-stepping the cursor is also provided for precise movement through a keyboard interface. The "h", "j", "k", and "l" keys are used to move the cursor left, down, up, and right one pixel respectively, in addition to the four arrow keys. Using the shift key in combination with the special or arrow keys, moves the cursor in the corresponding direction ten pixels.

Gray Level Matrix:
A 3X3 matrix of gray level values (or pixel intensity values). The center value is the gray level value of the current cursor position and the remaining matrix values represent those values immediately surrounding the center pixel.

Line/Sample:
A text field which displays a one-relative coordinate calculated from the upper left corner of the displayed image. Therefore, the upper left coordinate will always be 1,1 and the lower right coordinate will be the size of the displayed image.

File Coordinate:
A text field which displays a one-relative line and sample coordinate calculated from the upper left corner of the orignal disk image. This coordinate may differ from the line/sample coordinate described above by the window loaded, the subsampling and/or the zoom factor applied.

Projection Coord:
A toggle button which when selected displays a coordinate respresenting the X/Y position of the cursor in the coordinate space defined by the map projection of the image. The corner coordinates, as well as the units these coordinates are specified in (e.g., meters), must be stored with the image for this option to function. An error message will be output to the user if the appropriate information is not available. Note: for LAS 5.0 images, this information is stored in the DDR of the image.

Lat/Long:
A toggle button which when selected displays a coordinate representing the latitude/longitude position of the cursor. XID uses the geometric transformation package GCTP to perform this calcula- tion. Therefore, the corner coordinates (in projection coordi- nates) of the image, as well as 15 projection parameters defining the projection, must be stored with the image for this option to function. An error message will be output to the user if the appropriate information is not available. Note: for LAS 5.0 images, this information is stored in the DDR of the image.

Unscaled:
A toggle button which when selected displays values representing an approximation of the original red, green, and blue gray level values of the current point. This option applies only if the original image data was two-byte integer, four-byte integer, or floating point data which requires the image data to be scaled at load time. These values are only approximations since the original values are not read from disk, but are calculated based on the scale and offset applied to the data when the image was loaded.
The original and mapped radio buttons allow the user to select how gray level values are displayed.

Original:
The gray level values are to be displayed as the original values as they are loaded into the image planes (i.e., for non-byte data, the unscaled values are not displayed).

Mapped:
The gray level values are to be displayed as gray level values with the current mapping applied (i.e., mapped gray level values indicate how the value looks to the user, rather than the actual value).
The X/Y and Z radio buttons allow the user to select the dimension to cursor in.
X/Y:
Gray level values are reported for the currently displayed image. If a color image is displayed, red, green, and blue gray level values are displayed. If a single band black and white image is displayed, only the gray level values for that band are displayed.

Z:
Gray level values are reported for a single band at a time. The manual option is automatically enabled when the Z dimension is selected. The user chooses which band the values are displayed for, with the slider in the lower right corner of the panel. As the user moves the slider, values are updated for the current band. The current band is indicated by the slider.
The automatic and manual radio buttons allow the user to select the update mode for the cursor information panel.

Automatic:
In automatic mode, the cursor panel information is updated each time the user moves the mouse within an image window.

Manual:
In manual mode, the cursor panel information is updated only when the user clicks the right mouse button in an image window.
Dismiss:
Close the cursor panel.