Deskewing a scanned image

Skew is an artifact that might appear during document scanning process and it consists of getting the document’s text/images be rotated at a slight angle. It can have various causes but the most common are paper getting misplaced during a scan. Therefore, deskew is the process of detecting and fixing this issue on scanned files (ie, bitmap) so deskewed images will have the text/images correctly and horizontally aligned.

Deskewing an image can help a lot, if you want to improve the readability of scanned images. For example, think of a camera that automatically takes photos of goods with a barcode. If the skew angle is too high, the barcode can not be detected. After deskewing, the barcode can be read.

String dataDir = "DataDir/";

String fileName = "skewed.png";
String output = "skewed.out.png";
String inputFileName = dataDir + fileName;

// Get rid of the skewed scan with default parameters
try (RasterImage image = (RasterImage)Image.load(inputFileName))
{
	image.normalizeAngle(false /*do not resize*/, Color.getLightGray() /*background color*/);
	image.save(dataDir + output);
}

Below is an example of skewed scanned text and deskewed output.

Skewed image	Deskewed image