ANIMATE takes a series of animation “frames” and
strings them
together as with celluloid film to make a “movie”. This may be an
animated real-life photograph or a flashing poster-colour sign.
The basis for these animations is GIF - the GRAPHICS INTERCHANGE FORMAT. This alone will support animation. It is true that there is the official MPEG system of digital TV, but few browsers support it.
GIF gives an automatic three-fold compression by limiting the choice of colours to 256, that is to say, one byte per colour rather than the three bytes in 16-megacolour BMP files. The subtlety of a photo can be lost, so always work with BMP files until the photo has been cut down to the smallest size. Converting to GIF at the last minute ensures that the palette (see right) contains colours that are actually used.
To obtain the three-fold compression, the palette -
also called the colour look-up-table - has to be sent with the file. This
costs 768 bytes for 256 colours.
Once the main picture (left) has been made, a series
of animations can be made from it (right). Note that unlike celluloid
film, GIF allows small parts of a frame to be animated. Be sure to
make the animations from the GIF file of the main picture so that the
same palette is used. IF THE PALETTES MATCH, Wehner`s ANIMATE.COM will
use the original table as “global”,
saving 768 bytes each time.
If you want a transparent colour, such as for the area around the main picture, it is best to standardise on colour zero - and to ensure that this never appears in the photograph itself. The clear colour MUST be specified to the program that makes the main image. The clear colour for each of the animations can be selected when using Wehner`s ANIMATE.COM.
For poster images it is good to use a
two-colour palette which takes up only six
bytes in the file.
The palette of the next frame
may also be six bytes. If different, it cannot
refer back to the global table, but codes so efficiently that it
saves more than six bytes. Wehner`s ANIMATE will detect the palette difference
and put the palette into the file as a “local” palette.
If the background colour was transparent, the result
for the second frame is as shown on the left.
As a consequence, a new colour has been laid upon
the old, so that multi-coloured images can be made from simple
two-colour palettes. Such files can be extremely small - and download
fast - yet fill the screen with colour and action.
Put all your components on one disk together with a copy of Wehner`s ANIMATE.COM, for ease of handling.
The next stage after the creation of the animation
frames is to go to the DOS prompt by whatever means you are accustomed
to.
You can now use the DOS prompt to go to the floppy
drive, with the command “A:”.
Then you can type ANIMATE NEWFILE,
where NEWFILE becomes the name of NEWFILE.GIF.
Now you can type the name of the main picture. You
have no control of the transparent colour, which should have been
prepared in advance, nor of any other parameter. The main image is
copied up as it is.
A series of questions is now asked. For example, the
eyes E1.GIF were 71 dots to the right and 86 dots down. You will have to
repeat the same answers if you are animating on the spot, or vary
them if you are animating different parts. Often, as with flashing
images, the answer will be zero in each case.
The timing figure is in 100ths of a second, and you can enter numbers up to 65535, giving 655 seconds - more than ten minutes. This could be used for a practical joke, when the image changes to something surprising if displayed for a very long time.
After a number such as 198 has been entered, giving 1.98 seconds, the computer asks whether the background should return. This can be handy for blinking eyes. The eyelids alone need be specified by the graphic, and the original eyes return afterwards.
Unfortunately, the computer has to allocate memory with MALLOC, and then unpick the bytes from the screen area and save them to that memory. It is processor intensive. Sometimes, the cursor can be seen to blink in step with the eyes, suggesting overload.
It is better to refuse, and after the fiftieth of a second blink (timing 2), put the eyes back in the next frame. After all, on those early browsers that do not support background replacement, the eyes would not blink but remain shut until overwritten. Avoiding background replacement therefore guarantees compatability, but at the expense of larger files.
The final question enables you to select the transparent colour for each overlay. It is hard to remember what the colours were, so it is best to standardise on colour zero for transparent. However, in some cases the file has already been made and cannot be altered, so the program gives you the option of entering any number from zero to 255.
Entering a non-numerical symbol, such as a letter of the alphabet - or entering nothing, which puts a CARRIAGE-RETURN in the buffer - will make the program compile the frame into the file with NO transparent.
The program announces NEXT FRAME, and it is at this point that you can enter nothing at all. If this is done, ANIMATE.COM will complete the NEWFILE and close. Otherwise, the system will cycle to build up the animation.
Note that all filenames must be DOS names. Thus, PROLIXITY.GIF will have to be entered under its eight-symbol DOS name PROLIX~1.GIF or similar, or it will not be found by the program.
The NEWFILE.GIF can be inserted into HTML documents exactly as if it were a still picture. Animation is intrinsic in the coding of the file, so no special treatment is needed.
The timing of the first frame should be long. This is
to allow the browser time to generate paper copy. If the rendering
occurs in mid-animation, the hard copy will be spoilt.
The animation will proceed in a continuous loop
against the background of the main picture. Virtually all internet
images are required to work this way. If you want the animation to
stop at the last frame, set the timing of that frame to NIL.
This gives infinite time.