make-image-from-port

make-image-from-port Function

Summary

Makes an image out of a specified rectangle of a graphics port's contents.

Package

graphics-ports

Signature

make-image-from-port port &optional x y width height => image

Arguments

`port`⇩	A graphics port.
`x`⇩	An integer.
`y`⇩	An integer.
`width`⇩	An integer.
`height`⇩	An integer.

Values

image

An image.

Description

The function make-image-from-port makes an image out of the specified rectangle of the port's contents. The default is the whole port, but a region can be specified by supplying x, y, width, and height. The default values of x and y is 0.

Normally the image is freed automatically, when port is destroyed. However there are circumstances where you need to explicitly free an image, for example when you want it to go away before the port. If the image is not freed, a memory leak occurs.

Notes

On macOS, port must be a pixmap-port (an error is signaled if port is an output-pane). This is also recommended for other platforms as well, because it might be impossible to get the correct pixel information from an output-pane.