3.2 Contrast Optimization in Radiographic Images
Radiogrphic films normally have deficient contrast after the test due to various problems like
nonuniform radiation caused by the inspection technique, variation in the thickness of the
inspected part, inadequate film exposure, and inadequate film processing control, among
others [7].
The digitization process of radiographs can also be responsible for the low contrast of the
digital image, mainly systems that do not have good gray level dynamics. Problems such as
out-of-focus, reflection and distortion must be controlled effectively. The electronic circuit of
the digitizing plate must prevent the decrease of the distribution of gray levels when digitizing
the images [8].
The objective of the contrast improvement stage in radiographs is to enhance the regions in
which there are defects, without affecting the other regions of the image, thereby guaranteeing
that the subsequent segmentation techniques can come out well. [21]. It should be noted thatthe radiographic contrast improvement stage comes after noise elimination, so that the noise is
not enhanced together with the contrast.