NAME
AnimateImages
DESCRIPTION
This module is basically an animation builder and player for the Explorer
environment. It accepts images in byte lattices (usually snapped out of
the Render module) and buffers them into an internal image list. Images
can be interactively added and deleted from this list as necessary,
although there is no provision for image reordering.
Once images are accumulated in the list, the sequence can be played
back in a custom 24-bit (or 12-bit) window on the module's control
panel using various options. There are controls for single stepping,
going forwards and backwards, jumping to a particular image, adjusting
the animation delay, looping, buffering the images to memory or disk,
optimizing for speed or memory, etc. One of the most important options
is the ability to save single images (or all of them) in the list as SGI RGB
files (RLE-compressed, of course) for later compilation into a real
animation file.
The maximum playback speed of the animation is, of course, entirely
dependent on the host machine's CPU and graphics subsystem. Here
are some sample timings for all the combinations of options. They were
run using an 8-frame, 640x480 animation on a 200Mhz SGI Indigo2 with
an XZ graphics card (single-buffering = 24-bit and double-buffering =
12-bit):
Singlebuffering
to memory
optimized for speed
updating frame slider: 29.52 fps
not updating frame slider: 38.25 fps
optimized for memory
updating frame slider: 8.95 fps
not updating frame slider: 9.93 fps
to disk
optimized for speed
updating frame slider: 13.31 fps
not updating frame slider: 15.44 fps
optimized for memory
updating frame slider: 7.09 fps
not updating frame slider: 7.90 fps
Doublebuffering
to memory
optimized for speed
updating frame slider: 27.30 fps
not updating frame slider: 35.72 fps
optimized for memory
updating frame slider: 8.87 fps
not updating frame slider: 9.90 fps
to disk
optimized for speed
updating frame slider: 12.27 fps
not updating frame slider: 15.29 fps
optimized for memory
updating frame slider: 6.98 fps
not updating frame slider: 7.85 fps
INPUTS
Image -- Lattice (Opt.)
(2-D, 3..4-vector, byte, uniform).
This is an input image lattice.
WIDGETS
View Window? -- Option Menu
This determines whether the image window is visible or not. Most
functions on the control panel can still be used even if the window is
not visible. The notable exceptions being the "Refresh", "Prev",
"Play / Pause", and "Next" buttons.
Image Mode -- Option Menu
This sets the mode for adding new images to the image list. In "Add"
mode, whenever a new image lattice is received on the Image port it is
appended to the end of the image list. In "Freeze" mode, new lattices
are just ignored.
Image # -- Slider
This is the current image number. It can be used to go directly to any
particular image.
Play Mode -- Option Menu
This sets the direction for playing the images. They can be played
forwards, backwards, or in a forward and backward sequence (rocking).
Loop? -- Option Menu
This determines whether the images are played in a continuous looping
manner. In "Forward" mode, once the last image is reached it starts
over at the first image. In "Backward" mode, once the first image is
reached it starts over at the last image. In "Rock" mode, once the end
or the beginning of the image list is reached it switches playing
directions. The "Loop?" setting will also affect the behavior of the
"Prev" and "Next" buttons when reaching the bounds of the image list.
Step -- Slider
This is the increment to be applied to the current image number for
going forward or backward between images. It affects the functionality
of the "Prev", "Play / Pause", and "Next" buttons.
Delay (Sec.) -- Slider
This is the number of seconds to wait between playing images.
Save -- Text
This port is used in conjunction with the "Save Current Image"
selection in the "Options" menu; it probably should not be used
directly. The "Save Current Image" selection prompts for a name which
will be used to save the current image as an SGI RGB file (with RLE
compression).
Save All -- Text
This port is used in conjunction with the "Save All Images" selection in
the "Options" menu; it probably should not be used directly. The
"Save All Images" selection prompts for a name which will be used as
the basis to save all the images in the image list as SGI RGB files (with
RLE compression). For each image, the entered name is appended with
the image number (starting at 1) and a ".rgb" extension.
Background Color -- Text
This port is used in conjunction with the "Black Background" and
"White Background" selections in the "Options" menu. They set the
color of the background behind the images to black and white
respectively. A string parameter can be connected to this port
specifying three numbers (ranging from 0.0 to 1.0) for the red, green,
and blue components of the background color.
Center Images? -- Option Menu
This port is used in conjunction with the "Center Images" and
"Don't Center Images" selections in the "Options" menu. They
determine whether or not the images are centered within the entire
image window. The default is to place them in the lower left-hand
corner.
Update Frame Slider? -- Option Menu
This port is used in conjunction with the "Update Frame Slider" and
"Don't Update Frame Slider" (the default) selections in the "Misc."
menu. They determine whether the "Image #" slider (the current frame)
is updated as an animation is playing. Not updating this slider can
result in a significant speed increase with certain options.
Window Mode -- Option Menu
This port is used in conjunction with the "Single-buffered Window" (the
default) and the "Double-buffered Window" selections in the "Image"
menu. They determines how the images will be drawn in the image
window. Double-buffering mode will result in smoother animation, but
lower color resolution (12-bit). Single-buffering mode will result in
somewhat jerky playback, but full color resolution (24-bit). Also, the
speed using double-buffering mode will be somewhat less on graphics
hardware that doesn't do it in 24-bit, since the color resolution of the
original 24-bit images must be scaled down before they are displayed.
Buffer Storage -- Text
This port is used in conjunction with the "Buffer Images To Memory"
(the default) and "Buffer Images To Disk" selections in the "File" menu.
If disk buffering is selected then a file requester pops up asking for
a valid directory to store the image buffers. Changing from one
buffering mode to another automatically switches over all the buffered
images so that nothing gets lost.
Optimize -- Option Menu
This port is used in conjunction with the "Optimize For Speed" (the
default) and "Optimize For Memory" selections in the "Misc." menu.
When optimizing for speed, it tells AnimateImages to store each image
using four bytes per pixel. When optimizing for memory, it specifies
using only three bytes per pixel for each image. Using three bytes per
pixel is more memory/disk efficient (the fourth alpha component is not
really used anyway), but it slows down the playback speed since this
"compressed" format must be uncompressed before display. Speed
can improve significantly by using four bytes per pixel instead of three!
Note: Changing this setting doesn't affect the images already in the
image list, only new ones that are later added.
Timing -- Option Menu
This port is used in conjunction with the "Print Play Speed" and
"Don't Print Play Speed" (the default) selections in the "Misc." menu.
They determine whether timing information is printed to show playback
speed of an animation sequence. If selected then it prints the number
of frames displayed, the execution time, and the number of frames per
second achieved during a run.
Status -- Text
This string contains status information for AnimateImages. It shows
how many bytes have been allocated for the image list, the mode of the
image window (single/double-buffered), and how the images have been
buffered (memory/disk).
Button Window 1 -- Drawing Area
This is a custom drawing area containg the "Prev", "Play / Pause", and
"Next" buttons. The buttons perform the following tasks:
Prev - Go to the previous image considering the "Step" value. If
looping is enabled then stepping before the first image will cause a
wrap-around to the end of the image list.
Play / Pause - Play the images based on the "Play Mode" and the
"Step" value. Pressing this button again while the images are
playing will pause the sequence at the current image.
Next - Go to the next image considering the "Step" value. If looping
is enabled then stepping after the last image will cause a wrap-
around to the beginning of the image list.
Button Window 2 -- Drawing Area
This is a custom drawing area containg the "Add", "Delete", and
"Delete All" buttons. The buttons perform the following tasks:
Add - Forces the addition of an image lattice on the "Image" port to
the end of the image list regardless of the "Image Mode".
Delete - Deletes the current image from the image list.
Delete All - Deletes all the images in the image list.
NOTE: There is no undo capability so caution should be taken when
deleting images.
Button Window 3 -- Drawing Area
This is a custom drawing area containing the "Refresh" button.
Pressing it updates the contents of the image window. If the image
window is blocked by another window and then exposed, it will not be
automatically refreshed. Jumping to another image, playing the
animation, or deleting an image are the other ways that it will be
refreshed.
KNOWN PROBLEMS
The module may only work on SGI machines because it uses the Iris GL
library for displaying the images, the SGI image library for saving them,
and the SGI system call "sginap" to create the delay. When a window is
obscured then exposed, it will not be automatically refreshed. A future
version may alter this behavior, thus eliminating the need for a "Refresh"
button. Doublebuffering is hardcoded as being 12-bit for the XZ card.
This will change in the next version to take advantage of better graphics
hardware. There are no known bugs.
SEE ALSO
ExportImage, WriteImg, WriteMovie, WriteSGI
-
Hans Vahlenkamp (Hans.Vahlenkamp@noaa.gov)
Geophysical Fluid Dynamics Laboratory / NOAA
Princeton University Forrestal Campus
http://www.gfdl.noaa.gov
