At present much research is being done trying to develop an automatic (or semiautomatic)
system for the detection and classification of continuous weld defects examined by X-rays.2
However, it is pertinent to ask: What is the state of the art of research in this subject? The
present paper has as its main purpose to make a brief and objective description of the state-ofthe-art
in automatic inspection of weld seams by digital radiography based on the publications
that have appeared over the last decades, comparing the various techniques that are used and
pointing out the possible trends in the development of this research over the coming years.
The paper, divided into two parts (Part I: image processing, and Part II: pattern recognition),
follows the outline shown in Figures 1 and 2, consisting basically of three stages: image
acquisition (the fisrt stage); preprocessing, segmentation, feature extraction and detection of
defects (the second stage); and classification of the defects found (the third stage) . The first
and the second stages will be covered in Part I, while the third will be detailed in Part II. Each
stage will be taken up separately, and a table will be made showing the main technical aspects
and results obtained by each author. As will be seen in this paper, automatic detection of weld
defects is still an unresolved research field, since there is a large variety of situations in which
the defects can not yet be recognized by computational algorithms.