Just Lisping around

[fuccaro]

Many years ago I tried to draw stereograms (like this: https://en.wikipedia.org/wiki/Autostereogram ). I used to use Lisp for drawing on AutoCAD’s screen, then I saved the resulted image. I remember at that time I was wondering if I could leave-out AutoCAD, to make AutoLisp to write the data directly into a bitmap file. It didn’t work, Lisp can’t write binary. But these days I returned to that (to writing files, not to stereograms). Lisp can’t write binary, but it can write ordinary text files. So after getting the file right, the rest is just a question of conversion.

I downloaded a free hex editor (https://mh-nexus.de/en/hxd/).

Now: I use Lisp from inside AutoCAD to write the text file. I open it with Notepad, copy/paste the data in the hex editor and from there I save the file with BMP extension. Here are two samples -converted to GIF with Irfanview (https://www.irfanview.com/) just for uploading in the Forum.

   

And here is a Lisp:

(defun c:bmp()
  (setq file (open "C:\\Users\\miklos.fuccaro\\Desktop\\MyBitmap.tXt" "W"))
  (setq null4 "00 00 00 00")

  
  ;		file header:
  (write-line "42 4d" file)		;Magic Bytes
  (write-line null4 file) 		;File size
  (write-line null4 file)		;Reserved 1+2	
  (write-line "36 00 00 00" file)	;Data offset	!

  ;		Image header:
  (write-line "28 00 00 00" file)	;Heder size
  (write-line "ff 00 00 00" file)	;image width	!
  (write-line "ff 00 00 00" file)	;image height	!
  (write-line "01 00" file)		;Color Planes
  (write-line "10 00" file)		;Bits / Pixel	!
  (write-line null4 file)		;No compressions
  (write-line null4 file)		;Image size
  (write-line null4 file)		;X pix per m
  (write-line null4 file)		;Y pix / m
  (write-line null4 file)		;Colors
  (write-line null4 file)		;Important colors
    
  ;		Pixel data:


  ;|
;		saturn
  (setq col1 "08 08" col2 "1d 00" col3 "ff 1c" cx 115 cy 100 rDisc 50 rX 97 rY 14 i 0)  
  (repeat 256
    (setq i (1+ i) j 0)
    (repeat 256
      (setq j (1+ j))
      (setq dx (- cx j) dy (- cy i) dx (* dx dx) dy (* dy dy))
      (setq onDisc (if (< (+ dx dy) (* rDisc rDisc)) 1 nil))
      (setq ell (+ (/ (* (- i cy) (- i cy)) (* rY rY 1.0)) (/ (* (- j cX) (- j cX)) (* rX rX 1.0))))
      (setq onEllipse (if (equal ell 1 0.4) 1 nil))
      (setq str (if onDisc col2 col1))
      (cond
	((and onEllipse (= str col1)) (setq str col3))
	((and onEllipse (= str col2) (< i cy)) (setq str col3))
	) 
      (write-line str file)
      )   
    )
|;

  ; tree
 (setq col1 "ff 2d" col2 "e0 03" col3 "00 1c" col4 "c0 09"r1 0.03 r2 0.65 i 256)  
  (repeat 256
    (setq i (1- i) j 0)
    (repeat 256
      (setq str (if (< i 200) col1 col4))
      (setq j (1+ j))
      (setq str (if (< (abs (- j 90)) (* (rem i (+ 45 (/ i 7))) r2)) col2 str))
      (setq str (if (< (abs (- j 90)) (* i r1)) col3 str))
      (write-line str file)
      )   
    )

  
  (close file)
  (princ "OK")
  (princ)
  )

 

[BIGAL]

I am sure have seen read byte , in lisp. The attached may give you some ideas, its just something I had, not sure if it even works. There should be a write byte somewhere.

 

USERBLOCK.LSP:                                        ; Convert the byte(at "po" position and has "len" length") to sty [a decimal number-num, or list, or stream or string-str)
USERBLOCK.LSP:                                        ; po: the position of the byte
USERBLOCK.LSP:                                        ; len: the length of the reading byte
USERBLOCK.LSP:                                        ;the 14th~17th record position + 30 byte record the image position
USERBLOCK.LSP:             )                          ;the byte length of the image
USERBLOCK.LSP:                             )          ;the pointer position, every 4 byte record a RGB color

USERBLOCK.LSP

Edited May 11, 2023 by BIGAL

[fuccaro]

Thanks for that! There is a pretty long code to decipher, it will keep me busy for next few days (or weeks?)

Have a nice day!