thin - should not request key press for each image process

[charles1997]

copying file: /mnt/l/summer2021/dst/dst_00075.JPG -> /mnt/l/summer2021/dst_thinned_20210603_113254)/dst_00075.JPG
src_dir='/mnt/l/summer2021/dst', src_name='dst_00078.JPG'
ccc

key press is requested