Triangle Mozaic

This is a way of creating a mozaic of triangles (instead of the usual squares) from a given image.

The right image is the result of processing the left image with the code below.

rem
rem This is an example of image manipulation software written in Basic
rem using the freeware Macintosh METAL basic interpreter.
rem 
rem This program creates a mozaic from a given image.  Instead of identical
rem squares of fixed color, this program uses triangles (just those traditional
rem squares sliced diagonally).  Very simple, but nice result.
rem
rem Metal seems to have a problem with very large images, so try this on
rem relatively small ones, say 600 x 500 or smaller.
rem
rem Matthew M. Conroy, 2001.  
rem Do whatever you want to with this code, especially improve it.
rem

file$ = open preview dialog$
get quicktime pict size file$,picW,picH

resize console 20,50,picW+20,picH+50
 load quicktime pict file$

virtu = init screen (0,0,picW+0,picH+0)
set screen to virtu
cls
copyrect 0,0,picW,picH,0,0,picW,picH,0,0,virtu

set screen to console
cls

squareSize=10

xLim = int(picW/squareSize)
yLim = int(picH/squareSize)

for i=0 to xLim-1
for j=0 to yLim-1

redSum=0: greenSum=0: blueSum=0
redSum2 = 0: greenSum2 = 0: blueSum2 =0 

set screen to virtu

rem *****  do upper triangles

for x = i*squareSize+1 to (i+1)*squareSize
for y = j*squareSize+1 to j*squareSize+1+x-i*squareSize-1
get pixel x,y,red,green,blue
redSum= redSum+red
greenSum = greenSum + green
blueSum =blueSum + blue
next y
next x

meanRed = 2*redSum/((squareSize+1)*(squareSize+1))
meanGreen = 2*greenSum/((squareSize+1)*(squareSize+1))
meanBlue = 2*blueSum/((squareSize+1)*(squareSize+1))

for x = i*squareSize+1 to (i+1)*squareSize
for y = j*squareSize+1 to j*squareSize+1+x-i*squareSize-1
set screen to console
forecolor meanRed, meanGreen, meanBlue
plot x,y
next y
next x

rem **** do lower triangles

redSum=0: greenSum=0: blueSum=0

for x = i*squareSize+1 to (i+1)*squareSize
for y = j*squareSize+1+((x-i*squareSize-1)) to (j+1)*squareSize

set screen to virtu
get pixel x,y,red,green,blue

redSum= redSum+red
greenSum = greenSum + green
blueSum =blueSum + blue

next y
next x

meanRed = 2*redSum/((squareSize+1)*(squareSize+1))
meanGreen = 2*greenSum/((squareSize+1)*(squareSize+1))
meanBlue = 2*blueSum/((squareSize+1)*(squareSize+1))

for x = i*squareSize+1 to (i+1)*squareSize
for y = j*squareSize+1+((x-i*squareSize-1)) to (j+1)*squareSize
 
set screen to console

forecolor meanRed, meanGreen, meanBlue
plot x,y

next y
next x
next j
next i