image_crop_click {plothelper}

Cut out a Subregion of an Image by Mouse Click

Description

This function is a wrapper of magick::image_crop. While the latter asks you to set a geometry parameter, this function enables you to set the four sides of a subregion only by click the mouse. You must click at least 2 times (that is, click on 2 different points to define a rectangle). After clicking, please press Esc on your keyboard. You can also designate an irregular polygon by mouse with at least 3 clicks. If it is irregular, you MUST click on positions in order (something like that, when you draw a polygon in R, you must input the positions of points in order).

Usage

image_crop_click(x, only_value = FALSE, rectangle = TRUE, trim = FALSE)

Arguments

x

an image read into R by magick::image_read or an image modified by functions in the magick package.

only_value

the default is FALSE, which will return the subregion. If you set it to TRUE, the result is only four values with the order: left, right, top, bottom.

rectangle

whether the cropped area is a rectangle (default is TRUE). If it is FALSE, the subregion can be irregular.

trim

this is only used when rectangle is FALSE. It decides whether the irregular subregion is to be trimmed. If it is FALSE (default), no trimming will be done. If it is a 0 to 100 value, magick::image_trim will be used, whose fuzz argument is equal to trim. If it is TRUE (not 1), trimming will be done according to the mouse click you have made.