Running examples in 'baRulho-Ex.R' failed
The error most likely occurred in:

> ### Name: master_sound_file
> ### Title: Create a master sound file
> ### Aliases: master_sound_file
> 
> ### ** Examples
> 
> {
+ # load example data from warbleR
+ data(list = c("Phae.long1", "Phae.long2", "Phae.long3", "Phae.long4", 
+ "lbh_selec_table"))
+ 
+ # save sound files to temporary folder
+ writeWave(Phae.long1, file.path(tempdir(), "Phae.long1.wav"))
+ writeWave(Phae.long2, file.path(tempdir(), "Phae.long2.wav"))
+ writeWave(Phae.long3, file.path(tempdir(), "Phae.long3.wav"))
+ writeWave(Phae.long4, file.path(tempdir(), "Phae.long4.wav"))
+ 
+ # make an extended selection table
+ est <- selection_table(X = lbh_selec_table, extended = TRUE, confirm.extended = FALSE, 
+ path = tempdir())
+ 
+ # create master sound file
+ master.sel.tab <- master_sound_file(X = est, file.name = "example_master", 
+ dest.path = tempdir(), gap.duration = 0.3)
+ 
+ # the following code exports the selection table to Raven using Rraven package
+ # Rraven::exp_raven(master.sel.tab, path = tempdir(), file.name = "example_master_selection_table")
+ }
checking selections (step 1 of 2):

  |                                                  | 0 % ~calculating  
  |+++++++++++++                                     | 25% ~00s          
  |+++++++++++++++++++++++++                         | 50% ~00s          
  |++++++++++++++++++++++++++++++++++++++            | 75% ~00s          
  |++++++++++++++++++++++++++++++++++++++++++++++++++| 100% elapsed=00s  
all selections are OK 
saving wave objects into extended selection table (step 2 of 2):

  |                                                  | 0 % ~calculating  
  |+++++                                             | 9 % ~00s          
  |++++++++++                                        | 18% ~00s          
  |++++++++++++++                                    | 27% ~00s          
  |+++++++++++++++++++                               | 36% ~00s          
  |+++++++++++++++++++++++                           | 45% ~00s          
  |++++++++++++++++++++++++++++                      | 55% ~00s          
  |++++++++++++++++++++++++++++++++                  | 64% ~00s          
  |+++++++++++++++++++++++++++++++++++++             | 73% ~00s          
  |+++++++++++++++++++++++++++++++++++++++++         | 82% ~00s          
  |++++++++++++++++++++++++++++++++++++++++++++++    | 91% ~00s          
  |++++++++++++++++++++++++++++++++++++++++++++++++++| 100% elapsed=00s  
Error in warbleR::image_to_wave(file = file.path(tempdir(), "strt_mrkr-img.png"),  : 
  must install 'png' to use this function
Calls: master_sound_file -> <Anonymous>
Execution halted