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Screen Captures

In this exercise we are going to combine several things to add a useful link to your homepage: how to capture screen images to a PICT file, how to convert PICT format to GIF format (and rescale if necessary), and how to add a link to the resulting GIF image to your homepage.

The two pieces of software that we shall use are Flash-It, a screen capture shareware program for the Mac, and GifConverter, another Mac shareware program that is a valuable asset in converting and manipulating images.

Screen Capture with Flash-It

It is often important to be able to capture all or part of the computer display screen. For example, many of the illustrations in this tutorial started off as screen capture images. The standard Macintosh operating system incorporates a rudimentary screen capture function, but the shareware program Flash-It gives a richer set of possibilities.

Flash-It Capture Modes

Open the "Control Panels" in the System Folder and double-click on "Flash-It 3.0.2" to open it. The resulting display can be toggled between two screens: "Hotkeys" and "Options". The "Hotkeys" screen lists the ways in which a screen capture can be saved (see figure at right). All actions are initiated by simultaneously holding down the "Shift" and the "Apple" (the one with the cloverleaf symbol) keys and then hitting a third key. The possibilities are listed in the "Hotkeys" screen:

  1. "Shift + Apple + c" causes the capture to go to the clipboard.
  2. "Shift + Apple + 2" causes the capture to go to the scrapbook file.
  3. "Shift + Apple + 3" causes the capture to be stored in a file with name specified by user.
  4. "Shift + Apple + 4" sends the captured image to the printer.
  5. "Shift + Apple + 5" lets you decide "on the fly" what to do with the image.
  6. "Shift + Apple + 6" lets you send an image stored on the clipboard to a file or the printer.
  7. "Shift + Apple + 7" lets you reconfigure these keys.

The most useful option for our purposes will be "Shift + Apple + 3", which will allow us to capture all or part of the screen as a PICT image, and to store that image in a file.

Flash-It Options

If the Flash-It display is toggled to the "Options" page (figure at right), there are several choices to control how the screen is captured. We won't discuss them all (see the documentation that can be accessed through the "Help" button for more details). The most important for our discussion are

  1. The "Enable Flash-It" box, which should be checked.

  2. The box "Capture cursor" that determines whether the mouse cursor is captured in the image when the screen is captured.

  3. The "Capture tool": if "Marquee" is selected, you draw a rectangle around the portion of the screen to be captured with the mouse; if "Lasso" is selected a lasso tool appears that allows you to select the capture region by freehand drawing.

  4. The "When caps-lock is down, capture:" item, which allows you to select two special options by initiating a capture with the "Cap Locks" key down: (1) Automatic capture of the entire display, or (2) Automatic capture of the most recently selected window and its associated menu. For example, the screen images of windows shown on this page were captured using the second of these options.

For the examples we shall consider here, select the options shown in the preceding figure and close the Flash-It control panel.

Example: Capturing a Screen Image to a File

We are now going to perform an exercise in which we will add a short tutorial on the encoding program BinHex, complete with illustrative pictures, to our developing homepage. As a first step, let us capture two images of the main BinHex menu.

  1. Double-click on the BinHex 4.0 icon to open the program. Use the mouse to select the "File" pulldown menu, as illustrated in the adjacent image.

  2. While the mouse button is still held down, select from the keyboard with your other hand "caps lock", and then "Shift + Apple +3". This causes Flash-It to capture an image of the "File" pulldown menu.

  3. In the dialog box that pops up, select a name for the image file (we will assume a name "flashit.pict" for the discussion---unselect the "caps-lock" key to get lower case letters again), select "Desktop" for the location, and click "Save" (see figure below).

If you now look on the desktop, there should be a PICT image file called flashit.pict.

The preceding capture used the default (enabled by "caps lock") that captured an entire window and its associated menu. Let's now make another capture where we select explicitly the region to be captured. Repeat the above steps to capture the "File" menu of BinHex, except that this time

  1. Initiate the capture with the "caps lock" off ("Shift + Apple + 3").

  2. The preceding step leaves a "+" cursor displayed on the screen. Place the "+" cursor at one corner of the region you want to capture, hold the mouse button down, and drag a rectangle around the region to be captured. For this example, capture the region delimited by the red rectangle in the figure at the right from the "File" menu.

  3. Release the mouse button; in the dialog box that pops up, save the file as binhex2.pict on the Desktop. You can close BinHex now.

Converting Image Formats with GifConverter

We cannot use the images that you just captured directly "in-line" in a Web document because Web browsers do not generally display PICT format in-line. Thus, we must convert the images to either GIF or JPEG format, which are the standard formats that browsers can display in-line. We shall use the shareware program GifConverter to convert the PICT images to GIF format. In the process, we will also learn how to use GifConverter to resize and to crop images.



Open the file flashit.pict that you just created on the Desktop using GifConverter. Click on the image to select it (a banded box should appear around the image, indicating that it is selected). Pull down the "Image" window and select "Scale" (see figure at above left); this will pop up a dialog box like the one shown in the figure above right. In this figure you must specify the percentage of scaling in the vertical and horizontal direction. Select 90% for each and click "OK".

Now let's save our rescaled image in GIF format. Pull down the "File" menu and select "Save As" (left figure). This pops up the dialog box shown in the next image below. In this dialog box, select "GIF" for the format, select your homepage folder for the destination, give the file a name flashit.gif, and select "Save". This saves the image to the file GIF-format file flashit.gif in your homepage folder. You can throw away the original PICT image file flashit.pict on the Desktop by dragging it to the trash.

Now let's convert the other screenshot image that we took earlier. In the process, we shall see how to crop images with GifConverter. Open the file binhex2.pict created previously on the Desktop with GifConverter and click on the image to select it (see figure at left). Use the mouse button to select the cropping symbol (the "+" made from dashed lines that is circled in the adjacent image).

Hold the mouse button down to drag a rectangle around the part of the image that you wish to retain and release the mouse button (see figure at right). Then select "Crop" from the "Image" menu. This will crop the image, leaving only the part that was inside the cropping rectangle. Do a "Save As" like before, and save this as a GIF image in your homepage folder with the name binhex2.gif. At this point, you may throw away the Desktop file binhex2.pict.


A Simple Example: Making a BinHex Tutorial

Open your homepage file index.html in your home folder and insert the following HTML code at a convenient place: 

   <h2>Using BinHex</h2>
  
The encoding program
<tt>BinHex</tt> can be used to
encode binary files into ASCII.  Thus,
for example, a binary file can be sent
by email if it is first encoded with
<tt>BinHex</tt>, emailed, and
then decoded with
<tt>BinHex</tt> on the other
end.  <p>

<img src="binhex.gif" hspace="15"
vspace="5" align="left">
<tt>BinHex</tt> is easy to
use.  Open the program and select the
"File" pulldown menu (see figure at
left).  Then, if you wish to encode a
binary file, select "Application -->
Upload", and give the name of the file
in the resulting dialog box.  If you
wish to decode a file already encoded
with <tt>BinHex</tt>, select
"Download --> Application" and give
the name of the file in the resulting
dialog box.  <p>
For example, to encode a binary
sound file for emailing, you would
select <img src="binhex2.gif">
from the "File" menu and give the
name of the file in the resulting
dialog box.  The default name of the
encoded file is the original file
name with the extension ".hqx"
appended to it, and it is placed in
the same directory as the original
file.

Save the file index.html, point the browser at it, and reload. You should then have something like the following on your homepage:


Using BinHex

The encoding program BinHex can be used to encode binary files into ASCII. Thus, for example, a binary file can be sent by email if it is first encoded with BinHex, emailed, and then decoded with BinHex on the other end.

BinHex is easy to use. Open the program and select the "File" pulldown menu (see figure at left). Then, if you wish to encode a binary file, select "Application --> Upload", and give the name of the file in the resulting dialog box. If you wish to decode a file already encoded with BinHex, select "Download --> Application" and give the name of the file in the resulting dialog box.

For example, to encode a binary sound file for emailing, you would select from the "File" menu and give the name of the file in the resulting dialog box. The default name of the encoded file is the original file name with the extension ".hqx" appended to it, and it is placed in the same directory as the original file.


In this HTML example, the image tag 

<img src="binhex.gif" 
hspace="15" vspace="5" align="left">

places the image binhex.gif inline, aligned left (with text wrapping around it on the right), allowing 15 points of extra horizontal space and 5 points of extra vertical space around the figure (there are 72 points in an inch). The construction <tt> BinHex </tt> says to render the word "BinHex" in "teletype font" (a fixed-width font often used to signify the name of a computer program). The remaining HTML in this example should be familiar from previous exercises.

Assignment: Use the preceding as a guide; go back to the BinHex program, take screen shots of the dialog boxes that result when you choose "Download --> Application" or "Application --> Upload", and incorporate these images into the BinHex tutorial you have just placed on your homepage.

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