5 GIF and Animated GIF Writing
Writes the given bitmap
as a GIF image,
is either an instance of bitmap%
thunk (to be called just once) that generates such an object. If the
bitmap uses more than 256 colors, it is automatically quantized using
a simple algorithm; see quantize
. If the bitmap has a mask
bitmap via get-loaded-mask
, it is used to determine
transparent pixels in the generated GIF image.
Writes the bitmaps in bitmaps
animated GIF. The bitmaps
list can contain a mixture of
objects and thunks (each called just once) that
objects. The delay-csec
the amount of time in 1/100s of a second to wait between transitions.
is a true value, then the GIF is marked as a looping
If one-at-a-time? is #f, then the content of all
images is collected and quantized at once, to produce a single
colortable; a drawback to this approach is that it uses more memory,
and it allows less color variation among animation frames. Even when
one-at-a-time? is #f, the result of each thunk in
bitmaps is converted to a byte-string one at a time.
If one-at-a-time? is true, then the bitmaps are quantized and
written to the file one at a time; that is, for each thunk in
bitmaps, its result is written and discarded before another
thunk is called. A drawback to this approach is that a separate
colortable is written for each frame in the animation, which can make
the resulting file large.
If last-frame-delay is not false, a delay of
last-frame-delay (in 1/100s of a second) is added to the last
frame. This extra delay is useful when loop? is true.