| defines {magick} | R Documentation |
Set encoder defines
Description
So called 'defines' are properties that are passed along to external filters and libraries. Usually defines are used in image_read or image_write to control the image encoder/decoder, but you can also set these manually on the image object.
Usage
image_set_defines(image, defines)
Arguments
image |
magick image object returned by |
defines |
a named character vector with extra options to control reading.
These are the |
Details
The defines values must be a character string, where the names contain
the defines keys. Each name must be of the format "enc:key" where the
first part is the encoder or filter to which the key is passed. For
example "png:...." defines can control the encoding and decoding of
png images.
The image_set_defines function does not make a copy of the image, so the defined values remain in the image object until they are overwritten or unset.
See Also
Other image:
_index_,
analysis,
animation,
attributes(),
color,
composite,
device,
edges,
editing,
effects(),
fx,
geometry,
morphology,
ocr,
options(),
painting,
segmentation,
transform(),
video
Examples
# Write an image
x <- image_read("https://jeroen.github.io/images/frink.png")
image_write(x, "frink.png")
# Pass some properties to PNG encoder
defines <- c("png:compression-filter" = "1", "png:compression-level" = "0")
image_set_defines(x, defines)
image_write(x, "frink-uncompressed.png")
# Unset properties
defines[1:2] = NA
image_set_defines(x, defines)
image_write(x, "frink-final.png")
# Compare size and cleanup
file.info(c("frink.png", "frink-uncompressed.png", "frink-final.png"))
unlink(c("frink.png", "frink-uncompressed.png", "frink-final.png"))