# 用R语言绘制属于你的《红黄蓝灰格子》

Contents

## 引

1922年的《红、蓝、黄、黑构图》，将蒙德里安推向了绘画生涯的第一次巅峰。这幅作品虽然没有采用常见的平衡构图方式，却体现了他在不规则中寻找平衡的艺术思想。有人说，“蒙德里安意味着现代主义，他就是现代主义起源时期的图腾。”有他的地方，就有前沿艺术，就有对世界本源的探索，也许这就是蒙德里安的意义所在。

## The Mondrianomies

``````library(gsubfn)
library(tidyverse)

# Number of symbols in rule
s <- sample(15:26, 1)
# Extract s symbols from c("F", "+", "-") randomly
v1 <- sample(c("F", "+", "-"), size = s, replace = TRUE, prob = c(10,12,12))
# Add 3 pairs of brackets
v2 <- sample("[]", 3, replace = TRUE) %>% str_extract_all("\\d*\\+|\\d*\\-|F|L|R|\\[|\\]|\\|") %>% unlist
# Where to insert brackets
v3 <- sample(1:(s+1), size = length(v2)) %>% sort
# Insert them correctly
for(i in 1:length(v3)){
c(v1[1:(v3[i] + i - 1)], v2[i], v1[(v3[i] + i - 1):length(v1)]) -> v1
}

axiom <- "F-F-F-F"

# Rule to substitute F, as generated previously
rules <- list("F"=paste(v1, collapse=""))

# Turning angle
angle <- 90

# Haw many times to apply the rule
depth <- sample(3:4,1)

# Longitude (factor) of the segments
ds <- jitter(1)

# Substitute axiom depth times
for (i in 1:depth) axiom <- gsubfn(".", rules, axiom)

# Actions that will gneerate the drawing
actions <- str_extract_all(axiom, "\\d*\\+|\\d*\\-|F|L|G|R|\\[|\\]|\\|") %>% unlist

# These vars store the current position, angle and longitude factor of the point
x_current <- 0
y_current <- 0
a_current <- 0
d_current <- 0

# To store point position, angle and longitude
status <- tibble(x = x_current,
y = y_current,
alfa = a_current,
depth = d_current)

# To store segments
lines <- data.frame(x = numeric(),
y = numeric(),
xend = numeric(),
yend = numeric())

# This loop reads actions and generates the drawing depending on the concrete action
# F -> draw forward
# + -> turn right
# - -> turn left
# [ -> save the current status of point
# ] -> restore the last current status of point and remove from stack
for (action in actions)
{
if (action=="F") {
lines <- lines %>% add_row(x = x_current,
y = y_current,
xend = x_current + (ds^d_current) * cos(a_current * pi / 180),
yend = y_current + (ds^d_current) * sin(a_current * pi / 180))
x_current <- x_current + (ds^d_current) * cos(a_current * pi / 180)
y_current <- y_current + (ds^d_current) * sin(a_current * pi / 180)
d_current <- d_current + 1
}

if (action=="+") {
a_current <- a_current - angle
}
if (action=="-") {
a_current <- a_current + angle
}

if (action=="[") {
status <- status %>% add_row(x = x_current,
y = y_current,
alfa = a_current,
depth = d_current)
}

if (action=="]") {
x_current <- tail(status, 1) %>% pull(x)
y_current <- tail(status, 1) %>% pull(y)
a_current <- tail(status, 1) %>% pull(alfa)
d_current <- tail(status, 1) %>% pull(depth)
}
}

lines %>%
mutate(x = round(x, 1),
y = round(y, 1),
xend = round(xend, 1),
yend = round(yend, 1)) %>%
distinct(x, y, xend, yend) -> lines
select(lines, x3 = x, y3 =y) %>%
bind_rows(select(lines, x3 = xend, y3 =yend)) %>%
distinct(x3, y3) -> points

# Let's find squares to fill inside the drawing
# Since this operation maybe hard to compute, I divide points into
# 10 pieces to process them separately

n <- 10
split(points, rep(1:ceiling(nrow(points)/n),
each = n,
length.out = nrow(points))) -> points_divided

# Squares1: add X3, y3 to current segments and filter to find
# right angles

lapply(points_divided, function(sub) {
sub %>%
crossing(lines) %>%
filter(x == x3 | y == y3 | xend == x3 | yend == y3) %>%
filter(x != x3 | y != y3 , xend != x3 | yend != y3) %>%
mutate(id = row_number())
}) %>% bind_rows() -> squares1

# Squares2: keep those squares where some of new sides exist in lines
bind_rows(
squares1 %>%
inner_join(lines, c("x" = "x",
"y" = "y",
"x3" = "xend",
"y3" = "yend")),
squares1 %>%
inner_join(lines, c("xend" = "x",
"yend" = "y",
"x3" = "xend",
"y3" = "yend")),
squares1 %>%
inner_join(lines, c("x3" = "x",
"y3" = "y",
"x" = "xend",
"y" = "yend")),
squares1 %>%
inner_join(lines, c("x3" = "x",
"y3" = "y",
"xend" = "xend",
"yend" = "yend"))) %>%
distinct(x, y, xend, yend, x3, y3, id) -> squares2

# Remove those whose sides form a straight line

squares2 %>%
anti_join(squares2 %>% filter(x == xend, xend == x3),
by = c("x", "y", "xend", "yend", "x3", "y3", "id")) -> squares2
squares2 %>%
anti_join(squares2 %>% filter(y == yend, yend == y3),
by = c("x", "y", "xend", "yend", "x3", "y3", "id")) -> squares2

# We leave squares2 prepared for geom_rect

squares2 %>%
mutate(xmax = pmax(x, xend, x3),
xmin = pmin(x, xend, x3),
ymax = pmax(y, yend, y3),
ymin = pmin(y, yend, y3)) %>%
mutate(A = (xmax - xmin) * (ymax - ymin) / 2) -> squares

# Piet mondrian's palette

colors <- c("#FEFFFA","#000002","#F60201","#FDED01", "#1F7FC9")

# To remove very small squares I calculate quantiles form its area

qnts <- quantile(squares\$A,
probs = seq(0, 1, 0.05),
na.rm = FALSE,
names = TRUE,
type = 7)

# Here comes the magic of ggplot

ggplot() +
geom_rect(aes(xmax = xmax,
xmin = xmin,
ymax = ymax,
ymin = ymin,
fill = id %% length(colors) %>% jitter(amount=.025)),
data = squares %>% filter(A >= qnts[1]), # remove small squares
lwd = 2,
color = "white") +
geom_segment(aes(x = x, y = y, xend = xend, yend = yend),
data = lines,
lwd = .65,
lineend = "square",
color = "#000002") +
theme_void() +
theme(legend.position = "none") +
coord_equal() -> plot

# Calculate dimensions of the picture for ggsave

width <- max(points\$x3) - min(points\$x3)
height <- max(points\$y3) - min(points\$y3)
whmax <- 8
if (width >= height) {
w <- whmax
h <- whmax * height / width
} else {
h <- whmax
w <- whmax * width / height
}

# Save the drawing with a random name

name <- paste(sample(letters,6), collapse = "")
ggsave(paste0("new/",name,".png"), plot, width = w, height = h)
``````