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39.17.10 Multi-Frame Images

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.

function image-multi-frame-p image​

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.

function image-current-frame image​

This function returns the index of the current frame number for image, counting from 0.

function image-show-frame image n \&optional nocheck​

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.

function image-animate image \&optional index limit​

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.

function image-animate-timer image​

This function returns the timer responsible for animating image, if there is one.