# Kernel density demonstration animation
# Michael Minn
# 26 March 2022

# https://unix.stackexchange.com/questions/415430/h-264-mpeg-4-from-png-frames-how-to-and-how-to-tune-compression

# ffmpeg -r 24 -f image2 -s 600x400 -start_number 0 -i temp/frame%03d.png -vcodec libx264 -crf 15 -pix_fmt yuv420p output.mp4


width=15
height=10
kernel.size = 1

set.seed(0)
points.x = c(rnorm(4, 2, 2), rnorm(4, 11, 2), rnorm(4, 5, 3))
points.y = c(rnorm(4, 7, 2), rnorm(4, 6, 2), rnorm(4, 2, 2))

for (cell in 0:((width*height) - 1)) {
	png(sprintf("temp/frame%03d.png", cell), width=600, height=400)

	par(mar=c(0,0,0,0)) 

	plot(0, 0, col="white", xlim = c(0, width), ylim=c(0,height))

	for (z in 0:cell) {
		xleft = z %% width
		ybottom = floor(z / width)
		xright = xleft + 1
		ytop = ybottom + 1

		k.left = xleft - 1
		k.right = xleft + 2
		k.bottom = ybottom - 1
		k.top = ybottom + 2

		point.count = sum((points.x >= k.left) &
			(points.x <= k.right) &
			(points.y >= k.bottom) &
			(points.y <= k.top))

		col = rgb(colorRamp(c("white","navy"))(point.count/4)/255)	

		rect(xleft, ybottom, xright, ytop, col=col, border="lightgray")
	}

	points(points.x, points.y, pch=16, col="red", cex=2)

	kernel.x = cell %% width
	kernel.y = floor(cell / width)

	rect(kernel.x - 1, kernel.y - 1, kernel.x + 2, kernel.y + 2,
		lwd=3, border="navy")

	dev.off()
	# Sys.sleep(0.5)
}