fungraph.scmlibrary 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
In addition to the procedures described in the textbook, there are two additional ones:
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.
), i.e., the specified size is used as both the width and the height of the new 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
The images produced by
filled-triangle are of a size determined by the value of
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 separate windows, with numbered titles, like Img1, Img2. The title is also shown in the read-eval-print-loop's window, where the value normally would go. That way you can keep track of which image was generated by each evaluation.