This post describes my struggle to create a bitmap file with the Magick package. My assumption is that I should be able to specify each bit of a bitmap file. After some experimenting I can now create a bitmap file with contents more or less (but not exactly) what I want. The following code is used:
make_plot <- function (window_width, line_width, start=1, res=72) {
m2 = window_width / 2 ; m3 = window_width
fig <- magick::image_graph(
width = m3, height = m3, res = res)
parold = par(mar = c(0, 0, 0, 0))
plot.new()
plot.window(c(1, m3), c(1, m3))
rect(start, m3, m3, start,
border = 'black', lty = 1, lwd = line_width)
points( c(1, m2, m3), c(m3, m2, 1),
lty = 1, pch = 15, cex = line_width, col = 'red')
d <- dev.off()
par(parold)
fig
}
window_width = 72
line_width = 1
fig72 = make_plot(window_width, line_width)
So I create a graphical Magick device with 72*72 pixels. I also specify a res (resolution) of 72 but I am not sure if that has any impact.
I create a plot window corresponding to these values (a pixel per unit?) and set the margins to zero to avoid an'Error in plot.new() : figure margins too large' message.
I draw a rectangle in the outer pixels of the plot and draw three point in the left-upper, right-bottom and in the middle of the plot.
Then I close the device.
If we view the characteristics of fig72 and view the figure on the screen everything looks fine
magick::image_info(fig72)
#> # A tibble: 1 x 7
#> format width height colorspace matte filesize density
#> <chr> <int> <int> <chr> <lgl> <int> <chr>
#> 1 PNG 72 72 sRGB TRUE 0 72x72
fig72
but if we write the figure to a bitmap file
magick::image_write(fig72,path='fig72.bmp',format = 'bmp')
and view the file in an enlarged format with the Microsoft tools Paint and Snipping Tool we see the following
Case with 400 pixels instead of 72
Maybe with a greater number of pixels this will work fine? Let us try 400 pixels:
window_width = 400
line_width = 1
fig400 = make_plot(window_width, line_width)
Again writing the plot to a file
magick::image_write(fig400,path='fig400.bmp',format = 'bmp')
and viewing the file in an enlarged format we again see that the points and lines take more than one pixel:
Case with 400 pixels instead of 72 and line_width 0.01
And if we try a smaller line_width as e.g. 0.01
window_width = 400
line_width = 0.01
fig400_2 = make_plot(window_width, line_width)
Again writing the plot to a file
magick::image_write(fig400_2,path='fig400_2.bmp',format = 'bmp')
and viewing the file in an enlarged format:
Case with 400 pixels instead of 72 and line_width 0.01 and start 0
and with start = 0
window_width = 400
line_width = 0.01
fig400_3 = make_plot(window_width, line_width, start=0)
Again writing the plot to a file
magick::image_write(fig400_3,path='fig400_3.bmp',format = 'bmp')
and viewing the file in an enlarged format:
Case with 400 pixels instead of 72 and line_width 0.01 and res 400
and with res = 400
window_width = 400
line_width = 0.01
fig400_4 = make_plot(window_width, line_width, res=400)
magick::image_info(fig400_4)
#> # A tibble: 1 x 7
#> format width height colorspace matte filesize density
#> <chr> <int> <int> <chr> <lgl> <int> <chr>
#> 1 PNG 400 400 sRGB TRUE 0 72x72
Again writing the plot to a file
magick::image_write(fig400_4,path='fig400_4.bmp',format = 'bmp')
and viewing the file in an enlarged format:
Testje
Het volgende plaatje toont dat rect de coordinaten van de plot aanneemt.
Blijkbaar doet plot.window ook iets met de coordinaten anders dan de pixel waarden overnemen.
png(file="../../static/post/2019-04-28-creating-bitmap-file-with-magick_files/testje1.png", bg="transparent")
plot(1:10)
rect(1, 5, 3, 7, col="white")
dev.off()
#> png
#> 2
Session Info
#> R version 3.6.0 (2019-04-26)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 18362)
#>
#> Matrix products: default
#>
#> locale:
#> [1] LC_COLLATE=English_United States.1252
#> [2] LC_CTYPE=English_United States.1252
#> [3] LC_MONETARY=English_United States.1252
#> [4] LC_NUMERIC=C
#> [5] LC_TIME=English_United States.1252
#>
#> attached base packages:
#> [1] stats graphics grDevices utils datasets methods base
#>
#> other attached packages:
#> [1] HOQCutil_0.1.10 jsonlite_1.6 glue_1.3.1 purrr_0.3.2
#> [5] xml2_1.2.2 ggspatial_1.0.3 ggplot2_3.2.1 sf_0.7-7
#> [9] dplyr_0.8.3 stringr_1.4.0 osmdata_0.1.1
#>
#> loaded via a namespace (and not attached):
#> [1] tidyselect_0.2.5 xfun_0.8 lattice_0.20-38
#> [4] vctrs_0.2.0 colorspace_1.4-1 htmltools_0.3.6
#> [7] utf8_1.1.4 rlang_0.4.0 e1071_1.7-0
#> [10] pillar_1.4.2 withr_2.1.2 DBI_1.0.0
#> [13] sp_1.3-1 readxl_1.3.1 lifecycle_0.1.0
#> [16] plyr_1.8.4 cellranger_1.1.0 munsell_0.5.0
#> [19] blogdown_0.15 gtable_0.3.0 rvest_0.3.4
#> [22] evaluate_0.14 knitr_1.24 prettymapr_0.2.2
#> [25] curl_4.0 class_7.3-15 fansi_0.4.0
#> [28] highr_0.8 Rcpp_1.0.2 KernSmooth_2.23-15
#> [31] backports_1.1.4 scales_1.0.0 classInt_0.3-3
#> [34] magick_2.2 captioner_2.2.3 fs_1.3.1
#> [37] png_0.1-7 digest_0.6.20 stringi_1.4.3
#> [40] rosm_0.2.5 grid_3.6.0 cli_1.1.0
#> [43] rgdal_1.4-4 tools_3.6.0 magrittr_1.5
#> [46] lazyeval_0.2.1 tibble_2.1.3 zeallot_0.1.0
#> [49] tidyr_1.0.0 crayon_1.3.4 pkgconfig_2.0.2
#> [52] lubridate_1.7.4 assertthat_0.2.1 rmarkdown_1.15
#> [55] httr_1.4.1 R6_2.4.0 units_0.6-2
#> [58] compiler_3.6.0