<html><title>Opening Viking Image Files</title><H1>Opening Viking Image Files</H1><BR><P><body><UL><B>Quick Steps: To Open a PDS (.img or .imq extensions) image</B><LI>Pull down <CITE>FILE </CITE> menu<LI>Select <CITE>Acquire - PDS</CITE><LI><CITE>Open</CITE> desired file</UL><BR><P><P>TIFF, PICT, PICS (for a stack of images) and a few other file formats are directly read and displayed using the <CITE>File - Open </CITE> command within NIH Image. Raw data (images without any encoding or header information) can also be read with the <CITE>File - Import </CITE> command. However, Viking Image Files are in the Planetary Data System (PDS) format (.img or .imq extensions) and can not be opened directly using the <CITE>File - Open </CITE> command. <B>You must use the PDS plug-in under the Acquire menu to read a Viking Image file</B> (.imq or .img extensions). Make sure the PDS plug-in is located in the Plug-ins folder and resides in the same folder as the application program. The PDS plug-in is already included in the "plug-ins" folder within Image1.60 folder. To access the PDS plug-in, simply pull down the File menu and select <CITE>ACQUIRE-PDS</CITE>. If you have enough memory on your computer (16 mb or more), you can run NIH-Image and load PDS images as you read this tutorial. <P><IMG SRC = "GIFPICS/OPEN/ACQUIRE.GIF"><P>Now you can choose the image file you want to open. These image files are located in the VOImages folder. <P><IMG SRC = "GIFPICS/OPEN/OPenPDSa.GIF"> <P>As you move the cursor over the image window, note that the coordinates and pixel values for the cursor position are displayed in the Info window. To set the coordinates so that the actual X and Y distances on the images are shown in kilometers, see the <A HREF="SetScale.htm">How to Measure Distances and Areas of Landforms on an Image </A> section of this tutorial. The LUT (Look-Up Table) window displays the current gray level or color look-up table. Move the cursor over the LUT window and observe that the pixel values are displayed in the Info window (255 or black at the bottom, and 0 or white at the top as the default, or 0 or black at the bottom and 255 or white at the top with the pixel values inverted - see above). <P>The Viking Images look "washed out" when opened. The next section shows you how to bring out details by adjusting the brightness and contrast levels of the images<BR><P> Use the balloon help once in NIH Image to see a description of the tools.<p>
