39.17.9 Showing Images

You can use an image descriptor by setting up the display property yourself, but it is easier to use the functions in this section.

function insert-image image \&optional string area slice

This function inserts image in the current buffer at point. The value image should be an image descriptor; it could be a value returned by create-image, or the value of a symbol defined with defimage. The argument string specifies the text to put in the buffer to hold the image. If it is omitted or nil, insert-image uses " " by default.

The argument area specifies whether to put the image in a margin. If it is left-margin, the image appears in the left margin; right-margin specifies the right margin. If area is nil or omitted, the image is displayed at point within the buffer’s text.

The argument slice specifies a slice of the image to insert. If slice is nil or omitted the whole image is inserted. Otherwise, slice is a list (x y width height) which specifies the x and y positions and width and height of the image area to insert. Integer values are in units of pixels. A floating-point number in the range 0.0–1.0 stands for that fraction of the width or height of the entire image.

Internally, this function inserts string in the buffer, and gives it a display property which specifies image. See Display Property.

function insert-sliced-image image \&optional string area rows cols

This function inserts image in the current buffer at point, like insert-image, but splits the image into rowsxcols equally sized slices.

Emacs displays each slice as a separate image, and allows more intuitive scrolling up/down, instead of jumping up/down the entire image when paging through a buffer that displays (large) images.

function put-image image pos \&optional string area

This function puts image image in front of pos in the current buffer. The argument pos should be an integer or a marker. It specifies the buffer position where the image should appear. The argument string specifies the text that should hold the image as an alternative to the default.

The argument image must be an image descriptor, perhaps returned by create-image or stored by defimage.

The argument area specifies whether to put the image in a margin. If it is left-margin, the image appears in the left margin; right-margin specifies the right margin. If area is nil or omitted, the image is displayed at point within the buffer’s text.

Internally, this function creates an overlay, and gives it a before-string property containing text that has a display property whose value is the image. (Whew!)

function remove-images start end \&optional buffer

This function removes images in buffer between positions start and end. If buffer is omitted or nil, images are removed from the current buffer.

This removes only images that were put into buffer the way put-image does it, not images that were inserted with insert-image or in other ways.

function image-size spec \&optional pixels frame

This function returns the size of an image as a pair (width . height). spec is an image specification. pixels non-nil means return sizes measured in pixels, otherwise return sizes measured in the default character size of frame (see Frame Font). frame is the frame on which the image will be displayed. frame nil or omitted means use the selected frame (see Input Focus).

variable max-image-size

This variable is used to define the maximum size of image that Emacs will load. Emacs will refuse to load (and display) any image that is larger than this limit.

If the value is an integer, it directly specifies the maximum image height and width, measured in pixels. If it is floating point, it specifies the maximum image height and width as a ratio to the frame height and width. If the value is non-numeric, there is no explicit limit on the size of images.

The purpose of this variable is to prevent unreasonably large images from accidentally being loaded into Emacs. It only takes effect the first time an image is loaded. Once an image is placed in the image cache, it can always be displayed, even if the value of max-image-size is subsequently changed (see Image Cache).

Images inserted with the insertion functions above also get a local keymap installed in the text properties (or overlays) that span the displayed image. This keymap defines the following commands:

+

Increase the image size (image-increase-size). A prefix value of ‘4’ means to increase the size by 40%. The default is 20%.

-

Decrease the image size (image-increase-size). A prefix value of ‘4’ means to decrease the size by 40%. The default is 20%.

r

Rotate the image by 90 degrees clockwise (image-rotate). A prefix means to rotate by 90 degrees counter-clockwise instead.

o

Save the image to a file (image-save).