Introduction
I made a simple package to encapsulate the dithering code from yesterday’s post.
The package is called dithr
and is available on github
The code expects a numeric matrix (all values in the range [0, 1]) as input and provides a matrix as output with only 0 and 1 values. It includes 10 pre-defined diffusion matrices in dithr::diffusion_matrix
.
At the moment it’s not really very user friendly, mostly because dealing with image data in R can be a bit of a pain.
There’s probably a great set of image packages out there I haven’t discovered yet! (let me know!)
Intallation
devtools::install_github('coolbutuseless/dithr')
Packages
To Do
- Serpentine error diffusion (i.e. alternating traversal direction every row)
Create a ggplot and save it as a PNG
p <- ggplot(iris) +
geom_histogram(aes(Sepal.Length, fill=Species), bins=10) +
scale_fill_brewer() +
theme_bw() +
theme(legend.position='none')
ggsave("hist.png", width=6, height=4, units = 'in', dpi = 100)
p
Load the image and convert to a matrix
im <- magick::image_read('hist.png') %>%
magick::image_convert(type='grayscale') %>%
magick::image_scale(geometry="75%")
m <- magick::as_EBImage(im)@.Data
dithr::plot_matrix(m)
Dither matrix using floyd steinberg.
dithered_matrix <- dithr::dither(m, edm = dithr::diffusion_matrix$floyd_steinberg)
dithr::plot_matrix(dithered_matrix)
Dithered pie chart (Atkinson dithering)
#-----------------------------------------------------------------------------
# Create and save pie chart
#-----------------------------------------------------------------------------
p <- ggplot(iris) +
geom_bar(aes(1, fill=Species)) +
coord_polar(theta='y') +
scale_fill_viridis_d() +
theme_bw() +
theme(legend.position='none')
ggsave("pie.png", width=6, height=4, units = 'in', dpi = 100)
#-----------------------------------------------------------------------------
# Load and prepare image
#-----------------------------------------------------------------------------
im <- magick::image_read('pie.png') %>%
magick::image_convert(type='grayscale')
#-----------------------------------------------------------------------------
# Extract matrix data
#-----------------------------------------------------------------------------
m <- magick::as_EBImage(im)@.Data
#-----------------------------------------------------------------------------
# Dither
#-----------------------------------------------------------------------------
dithered_matrix <- dithr::dither(m, edm = dithr::diffusion_matrix$atkinson)
dithr::plot_matrix(dithered_matrix)
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