The
large-scale waves and brightness difference is eliminated
by the low-pass filter and the structure of the sample is
eliminated by the high-pass filter. After back transformation,
the brightness of the picture is averaged
and converted into the wrinkle factor. This wrinkle
factor is written into the original image and the resulting
image is stored. The wrinkle factor for solid-color
textile samples was determined between 0 for completely
smooth surfaces and 128 for maximum wrinkling.
The optical wrinkle tester consisted of a flat plate,
two infrared light-emitting diode (LED) light bars
placed on the frame forming a 90 angle and a digital
camera. The working distance between the camera and
the flat plate (object) was 280 mm. Different sets of
LED lights illuminated the textile sample and highlighted
the wrinkles on the textile surface from different
states in stray light. Consistent illumination conditions
and background were maintained for the different tests.