1.0 File Interfaces

1. The user may select one of the images listed below the label Files: by clicking the left mouse button on the choice, and then clicking the OK button, or by simply double clicking the left mouse button on the choice.

2. The user may select an image from another directory by typing the directory specification into the box below the label File Filter: and pressing enter (or clicking on the Filter button). This displays a list of files from the directory specified. Directory navigation can also be done by clicking the left mouse button on a directory name in the the list below the Directories: label and then clicking on the Filter button (or by just double clicking on the directory name).

3. The user may also select an image (by clicking the left mouse button on the choice) and then enter a window and/or band specification. The image name selected appears in the text box below the label Selection:. The window and/or band specification may then be entered by clicking the left mouse button in the text box and entering the specification using standard LAS syntax (i.e., image_name(sl,ss,nl,ns:b1,b2,b3)). Finally, the user may type a LAS image name directly in the text box below the label Selection:.

Each band of the selected image is loaded into a separate memory plane and is subsampled, if necessary, to fit into the defined size of the memory plane. The layout function (found on the Setup menu) may be used to redefine the memory plane configuration and/or the viewport configuration. A scale and offset are also calculated and applied to the image data if the input data is not BYTE data.

XID has been designed to work with both 24-bit and 8-bit color displays. In order to display a 3-band color image on an 8-bit color display (PseudoColor visual), the 24 bits of image data must be compressed to 8 bits. The color compression algorithm used is a median cut color compression algorithm taken from code developed for NASA JPL by the California Institute of Technology in 1989. This algorithm produces an image with the specified number of colors along with a color map used to display the image. XID actually reduces the image to 200 colors (rather than 256) in order to reserve 56 colors for other operations. Single band black and white images are also reduced to 200 gray level values.

Display of images on 24-bit displays (DirectColor visual) requires less compression of the image data but still requires some compresssion in order to reserve a number of colors for other operations. Each band of a color image is essentially reduced to 7 bits resulting in a 21-bit (rather than 24-bit) image. As described for pseudocolor displays, a single band black and white image is reduced to 200 gray level values for output to a 24-bit display.

OK:

Accept the currently selected image and proceed with loading the image.

Filter:

Apply the currently selected filter.

Cancel:

Close the Load panel without loading an image.

1. The user may select one of the images listed below the label Files: by clicking the left mouse button on the choice, and then clicking the OK button, or by simply double clicking the left mouse button on the choice.

2. The user may select an image from another directory by typing the directory specification into the box below the label File Filter: and pressing enter (or clicking on the Filter button). This displays a list of files from the directory specified. Directory navigation can also be done by clicking the left mouse button on a directory name in the the list below the Directories: label and then clicking on the Filter button (or by just double clicking on the directory name).

3. The user may also select an image (by clicking the left mouse button on the choice) and then enter a window and/or band specification. The image name selected appears in the text box below the label Selection:. The window and/or band specification may then be entered by clicking the left mouse button in the text box and entering the specification using standard LAS syntax (i.e., image_name(sl,ss,nl,ns:b1,b2,b3)). Finally, the user may type an image name directly in the text box below the label Selection:.

For nonLAS images, the user is required to enter information describing the input image such as number of lines and number of samples (see below). After the appropriate information has been entered, each band of the selected image is loaded into a separate memory plane and is subsampled, if necessary, to fit into the defined size of the memory plane. The layout function (found on the Setup menu) may be used to redefine the memory plane configuration and/or the viewport configuration. A scale and offset are also calculated and applied to the image data if the input data is not BYTE data.

XID has been designed to work with both 24-bit and 8-bit color displays. In order to display a 3-band color image on an 8-bit color display (PseudoColor visual), the 24 bits of image data must be compressed to 8 bits. The color compression algorithm used is a median cut color compression algorithm taken from code developed for NASA JPL by the California Institute of Technology in 1989. This algorithm produces an image with the specified number of colors along with a color map used to display the image. XID actually reduces the image to 200 colors (rather than 256) in order to reserve 56 colors for other operations. Single band black and white images are also reduced to 200 gray level values.

Display of images on 24-bit displays (DirectColor visual) requires less compression of the image data but still requires some compresssion in order to reserve a number of colors for other operations. Each band of a color image is essentially reduced to 7 bits resulting in a 21-bit (rather than 24-bit) image. As described for pseudocolor displays, a single band black and white image is reduced to 200 gray level values for output to a 24-bit display.

OK:

Accept the currently selected image and pop up the Image File Information panel to obtain the information required to proceed with loading the image.

Filter:

Apply the currently selected filter.

Cancel:

Close the Load panel without loading an image.

# Header Bytes:

Enter the number of bytes to skip before image data is found. Pressing enter in this field automatically advances the cursor to the # Bands text field.

# Bands:

Enter the number of bands contained in the selected image. Pressing enter in this field automatically advances the cursor to the # Lines text field.

# Lines:

Enter the number of lines contained in each band of the selected image. Pressing enter in this field automatically advances the cursor to the # Samples text field.

# Samples:

Enter the number of samples contained in each line of the selected image. Pressing enter in this field automatically advances the cursor to the Apply button.

Byte:

The selected image contains pixel values of 8-bit unsigned integer (0 through 255).

Integer*2:

The selected image contains pixel values of 16-bit signed integer (-32768 through 32767).

Integer*4:

The selected image contains pixel values of 32-bit signed integer (-2147483648 through 2147483647).

Real*4:

The selected image contains pixel values of 32-bit signed real (system dependent).

BSQ:

Band sequential format.

BIL:

Band interleaved by line format.

Cancel:

Close the Image File Information panel without loading the selected image. The File Selection panel remains intact.

Apply:

Close both the Image File Information panel and the File Selection panel and proceed with loading the image. Note: If the Apply button is the currently active button (eg., this button becomes active when the user presses enter at the # Samples text field), the user may simply press enter to proceed with loading the image.