How to create a simple graphic using Common Lisp?

Question

I would like to create a graphic, some points and lines, possibly with colours, out of lists of numbers. What would be the simplest and efficient solution?

I suppose that a possibility would be to use the library imago but I was not very sucessfull with it until now when trying simple examples from https://quickdocs.org/imago like:

;; Create 400x100 px red RGB image
(imago:make-rgb-image 400 100 (imago:make-color 255 0 0))

Symbol "MAKE-GRAYSCALE-IMAGE" not found in the IMAGO package.

How could this work? Do you have any working example I could take a look at?

Answer 1

I made a library called Vectometry for this, and I find it pretty useful. It's vector-based, not pixel-based, and it only outputs PNG files, so its suitability depends on what kind of output you want.

Here's an example:

* (ql:quickload "vectometry")
...

* (in-package :vectometry)
#<PACKAGE "VECTOMETRY">

* (defun red-box (output-file)
    (let ((canvas (box 0 0 400 100)))
      (with-box-canvas canvas
        (set-fill-color (rgb-color 1.0 0.0 0.0))
        (clear-canvas)
        (save-png output-file))))
RED-BOX

* (red-box "~/red.png")
#p"/path/to/home/directory/red.png"

It follows a postscript- or pdf-style imaging model, with move-to, line-to, curve-to, perspective transforms, etc., so if you are familiar with those operations, it should not be too tricky to use.

Answer 2

In order to use the new constructors , you have to use a more recent version of the library. You need to git clone the repository inside ~/quicklisp/local-projects/ , and if you already loaded the system:

(delete-package :imago)

Also it can be useful to clean your cache:

$ find ~/.cache/common-lisp -type d -name "imago"

and delete the content.

Then, if you reload the library, it should be the newer version:

(ql:quickload :imago :verbose t)

Alternatively, you can keep your version and make class instances explictly:

(make-instance 'imago:grayscale-image ...)

The rest should work as described in the documentation and examples.