image_modify_rgb_v: Modify R, G, B Values according to V values
In plothelper: New Plots Based on 'ggplot2' and Functions to Create Regular Shapes

While the image_modify_rgb function modifies R, G, B with reference to the original values, image_modify_rgb_v also takes into account the brightness (V) values. It is similar to those apps which divide an image into a bright part and a dark part (and, for example, you can increase red in the bright part and decrease red in the dark part.

image_modify_rgb_v(
  x,
  fun_r = NULL,
  fun_g = NULL,
  fun_b = NULL,
  alpha = FALSE,
  rescale_v = NULL,
  result = "magick",
  res = 144
)

`x`	an image created by `magick::image_read` or other functions in package magick.
`fun_r, fun_g, fun_b`	a function or a list which designates an internal curve. See the Details part of `image_modify_hsv`.
`alpha`	whether to allow the output colors have transparency. Default is FALSE.
`rescale_v`	You can rescale the V values before modifying colors. A desired range of V values can be given, e. g., `rescale_v = c(0.2, 1)` which will make the smallest original value to be 0.2, and the largest, 1. Alternatively, it can be your own scaling function.
`result`	the default is "magick", the output is a magick picture. When it is "raster", a matrix is created which can be use as a raster for `ggplot2::annotation_raster`.
`res`	when the result is a magick picture, the `res` parameter used by `magick::image_graph`. Default is 144.

This function uses custom functions or internal curves to make modification. See the Details part of image_modify_hsv to know how to use them. Note: values will be coerced to be in the [0, 255] range with no warning. For example, the original value is 240 and it becomes 280 in the output, then it will be set to 255 automatically.

plothelper documentation built on July 2, 2020, 4:03 a.m.