||Your Skills: Viewing Digital Images
Loading and Saving an Image First, download the image Cydonia.1. If you have an Macintosh computer, the file will be saved to the Downloads Directory designated in your web browser. If you have a PC, you will be asked where to save the file. Save the file to an appropriate location. If your browser is so configured, the image will be saved and then opened in your designated image viewer. In either case, make sure you know where the saved version of the image is located.
Note: It is very important to have a saved version of the image you want to work on because in this activity you will learn how to mangle it beyond all hope of repair. However, if you have saved the image onto your hard drive or a floppy disk, you will be able to replace a mangled version with the original and start over. If, while working on an image you have made an irreparable mistake and wish to restore the original, you have two options in NIH Image: select File/Revert to Saved, or close the image by clicking in the small square in the upper left of the image or by selecting File/Close, and then reloading the image. If you choose to close the image, you must be careful to select No in the "Save changes to... " dialog box that will appear. If by accident you select Yes, you will replace the original saved version with the mangled version, and you will have to download the image all over again!
If NIH Image is not already open as a result of the download, find it on your Desk Top, Launcher, or hard drive and start it. Select File/Open and use the dialog box to relocate Cydonia.1. Click twice on the image file to open it. Now wait a few seconds for the image to appear.
Note: If you get the message "This xxxK image is larger than the xxxK Undo buffer. Many operations may fail or be undoable," then carry out the following procedure. If you do not get such a message, skip the procedure.
1. Write down the size of the image listed in the message.
Humm! Not much to look at, is it? Lots of black and white dots scattered over a grayish background. If you look closely, you can see a few faint features, but they certainly don't stand out. Don't be discouraged, though, there is a gold mine of information there that you can find just by using a few simple tools.
Viewing part or all of the image Unless you have a huge monitor, the image is larger than the screen and you can see only part of it. To see the whole image, click on the little Scale-to-Fit box in the upper right corner. Doing so shrinks the whole image to fit your screen. Click it again to get the image back to full size. To see any part of the image at full size, select the Scroll icon from the Tools box at upper left by clicking once on the icon. Your cursor now turns into a small hand. Move the cursor onto the image, and click-and-drag in any direction you want. The image will move in the direction you drag it (until you come to an edge of the image), bringing different parts of the image into view. When you see the area you want, just release. This operation may be repeated as often as you wish. Try it a few times until you get the feel for how it works.
Just for fun, click the Scale-to-Fit box, choose an area of the image that looks interesting, click to full size again, and try to find your chosen area using the Scroll tool.
Zooming on part of the image To enlarge a small section of the image, select the Zoom icon from the Tools box. Your cursor will turn into a small magnifying glass. If you look closely at the cursor, you will see a plus sign in the small circle of the magnifying glass. The plus sign means "zoom in." Move the cursor to any spot on the image and click once- the image enlarges. Click again, and the image enlarges again. To unzoom, hold down the Option key on the key board while you click. Look closely at the magnifying glass while you hold the Option key, and you will see a small minus sign. The minus sign means "zoom out."
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