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Some image files can contain more than one image. We say that there are multiple “frames” in the image. At present, Emacs supports multiple frames for GIF, TIFF, and certain ImageMagick formats such as DJVM.
The frames can be used either to represent multiple pages (this is usually the case with multi-frame TIFF files, for example), or to create animation (usually the case with multi-frame GIF files).
A multi-frame image has a property :index, whose
value is an integer (counting from 0) that specifies which frame
is being displayed.
This function returns non-nil if
image contains more than one frame. The actual
return value is a cons (nimages .
delay), where nimages is the
number of frames and delay is the delay in seconds
between them, or nil if the image does not
specify a delay. Images that are intended to be animated
usually specify a frame delay, whereas ones that are intended
to be treated as multiple pages do not.
This function returns the index of the current frame number for image, counting from 0.
This function switches image to frame number
n. It replaces a frame number outside the valid
range with that of the end of the range, unless
nocheck is non-nil. If
image does not contain a frame with the specified
number, the image displays as a hollow box.
This function animates image. The optional
integer index specifies the frame from which to
start (default 0). The optional argument limit
controls the length of the animation. If omitted or
nil, the image animates once only; if
t it loops forever; if a number animation stops
after that many seconds.
Animation operates by means of a timer. Note that Emacs
imposes a minimum frame delay of 0.01
(image-minimum-frame-delay) seconds. If the image
itself does not specify a delay, Emacs uses
image-default-frame-delay.
This function returns the timer responsible for animating image, if there is one.
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