/usr/include/dlib/image_transforms/ is in libdlib-dev 18.18-2build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/dlib/image_transforms/assign_image.h
/usr/include/dlib/image_transforms/assign_image_abstract.h
/usr/include/dlib/image_transforms/colormaps.h
/usr/include/dlib/image_transforms/colormaps_abstract.h
/usr/include/dlib/image_transforms/draw.h
/usr/include/dlib/image_transforms/draw_abstract.h
/usr/include/dlib/image_transforms/edge_detector.h
/usr/include/dlib/image_transforms/edge_detector_abstract.h
/usr/include/dlib/image_transforms/equalize_histogram.h
/usr/include/dlib/image_transforms/equalize_histogram_abstract.h
/usr/include/dlib/image_transforms/fhog.h
/usr/include/dlib/image_transforms/fhog_abstract.h
/usr/include/dlib/image_transforms/hough_transform.h
/usr/include/dlib/image_transforms/hough_transform_abstract.h
/usr/include/dlib/image_transforms/image_pyramid.h
/usr/include/dlib/image_transforms/image_pyramid_abstract.h
/usr/include/dlib/image_transforms/integral_image.h
/usr/include/dlib/image_transforms/integral_image_abstract.h
/usr/include/dlib/image_transforms/interpolation.h
/usr/include/dlib/image_transforms/interpolation_abstract.h
/usr/include/dlib/image_transforms/label_connected_blobs.h
/usr/include/dlib/image_transforms/label_connected_blobs_abstract.h
/usr/include/dlib/image_transforms/lbp.h
/usr/include/dlib/image_transforms/lbp_abstract.h
/usr/include/dlib/image_transforms/morphological_operations.h
/usr/include/dlib/image_transforms/morphological_operations_abstract.h
/usr/include/dlib/image_transforms/segment_image.h
/usr/include/dlib/image_transforms/segment_image_abstract.h
/usr/include/dlib/image_transforms/spatial_filtering.h
/usr/include/dlib/image_transforms/spatial_filtering_abstract.h
/usr/include/dlib/image_transforms/thresholding.h
/usr/include/dlib/image_transforms/thresholding_abstract.h