image_modify_rgb_v {plothelper}

Modify R, G, B Values according to V values

Description

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.

Usage

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

Arguments

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.

Details

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.