Image Skew Detection and Correction in Regular Images and Document Images

Abstract

During any Document scanning and processing of regular images in our daily life activities image skew is a very important part that should be kept in mind before processing the images. Skew is generally referred to the degree of rotation of an image in comparison with its actual position. So before proceeding to any further activity with the images we need to assure the skew of an image is correct or not. So detection of skew of an image would be the first thing to be applied to regular images some times and specially scanned documents when transforming them to appropriate format. There are different algorithms for detection of skew of an image that have been implemented in different kind of works. The basic and very commonly used one is Scan line based skew detection. In this technique several lines are passed through the image from left to right, right to left, top to bottom and bottom to top and then the number of black pixels encountered in different projection of line are counted. The projection with maximum black pixels encountered is to be taken to consider the skew of the image. There is another approaches like Hough transform, Base-point method etc. In Hough transform method the pixel value is calculated for each value of θ. The angle producing maximum variance is considered to be the skew angle of the image. These two algorithms have been implemented and the results have been represented to compare the accuracy