Math 217A - Spring 2002
Creating GIFs for Turn-in

Goals: Capture the output of OpenGL programs, create GIF files and thumbnail versions for previewing.

If you follow these instructions, especially watching out for the dimensions of the small thumbnail version, it will simplify Frank's job of creating the class web pages!

The instructions below are for PC's and Adobe Photoshop.   They should work on the APM basement lab computers at least.  If you use other systems, procedures will vary.

How to capture OpenGL output.  Make the output window the currently active window by clicking on it.  Press ALT-RIGHTSHIFT-PRINTSCREEN (three buttons).  Use the shift button on the right side of the keyboard to avoid an unwanted keyboard shortcut.  This copies the current window into the Cut/Paste buffer. 
    Then open a graphics program (Paint or Photoshop, say).  Create a new blank image that has the right size, and paste (Cntl-V) the graphics image into the window.  Save the file in whatever format is best for you.
    For Photoshop, to do the above, the default image size will match the contents of the cut/paste buffer.  So for Photoshop, you just create new image (File...New... or just Cntl-N) and accept the suggested image size.
    For best quality image, use as large an OpenGL window as will fit on your screen.  You might be able to increase the resolution of your screen if you want a larger image.

Saving GIF files from Photoshop.  The basement computers have Photoshop Version 5.0.  For these computers, save GIF files by choosing Export....GIF89a... from the File menu.  If you have Photoshop version 6.0, there is a Save for web... extry on the file menu that should be used instead.
   You may also save JPEG files.    These are generally larger than GIF files, but provide better quality pictures, including better quality colors.

Creating a thumbnail sketch.  To create the thumbnail sketch, we need you to resize the images exactly to the right size.  For this, do the following.

  1. Save your full resolution file.
  2. Choose the menu entry Image .... Image Size ... . Set the larger of the width and height to equal 200 pixels.  Keep the image proportions constrained.
  3. If your image is exactly square, it is now 200 x 200 pixels, and you can proceed to Step 3.  Otherwise, make it square as follows. 
    1. First, set the background color to black. You do this by swapping (if necessary) the black and white colors for the foreground and background near the bottom of the tall narrow window with icons for various tools.
    2. Second, choose the menu entry Image ... Canvas Size ... .  Set the other dimension up to 200 pixels also.  Keep the image centered (this is the default).
  4. You are now done.  Save out the low res file as Thumb.gif using the directions above. --- Be sure not to overwrite your high-res version!

Trimming off unwanted parts of your images:  You may optionally wish to remove unwanted borders from your image.  In Photoshop, it can be done using the Canvas Size... feature.