fungraph.ss library, which is also included as part
of the concabs.ss library, provides the procedures for
producing graphical images described in Concrete Abstractions.
Because these procedures operate like mathematical functions, we refer
to them as functional graphics, hence the name fungraph.
In addition to the procedures described in the textbook, there are three additional ones:
(write-image-as-epsf image filename)
(mirror-image image)
quarter-turn-right or invert, this
takes an image and makes another, related image. In the case of
mirror-image, the new image is the same size as the
original, and is formed by flipping the original image around a
vertical axis, as though it were viewed in a mirror.
(resize-image image width height)
(resize-image image size)
(resize-image image size size),
i.e., the specified size is used as both the width and the height
of the new image.
(resize-image image)
(resize-image image default-image-size default-image-size),
i.e., the width and height are both taken as the value of
default-image-size. As described below, this is the same
name that controls the size of the images created by line
and filled-triangle.
The images produced by line and
filled-triangle are of a size determined by the value of
the name default-image-size. Initially this name is
defined as 100. This is a compromise size, a bit small for the
fractals in chapter 4 and rather large for each basic block of the
quilts in chapters 1-3. You can redefine it to another value (which
must be an exact, positive integer) to suit your own needs. Or, you
can use the resize-image procedure described above. For
example, when defining the basic blocks for quilting, it may make
sense to do so as in the following example:
(define test-bb (resize-image (filled-triangle 0 1 0 -1 1 -1) 25))
The images produced by the procedures in this library show up in the
interaction window, the same way any other value would. On some
systems, it is possible to copy and paste them within DrScheme. Where
this is possible, you can then directly use them as input in other
expressions. However, you can't use images from other sources in this
way; for example, images inserted into DrScheme using the
Edit menu's Insert Image... option are
not usable as arguments to the procedures in the functional
graphics library.
As mentioned above, the images can only be copied and pasted within DrScheme on some systems. Further, they can't be saved out to files and loaded back in on any system. Both of these are symptoms of the same basic bug. We have an alternative implementation of the functional graphics package that works around this problem, but has some disadvantages of its own, described in its own web page.