Digital image processing techniques are typically classified into three categories. These categories include image generation, enhancement, and restoration. Generation techniques help project and recognize a scanned image, while the process of enhancing an image involves improving contrast, brightness and hue. Restoration techniques help eliminate and correct errors that do not accurately reflect the original picture.
Many scanners that transmit images into computer programs use optical character recognition (OCR) technology. This converts the original image into text that the computer program will recognize. One of the main problems with any type of image processing technology is that some degree of editing is needed. Simple programs allow users to manipulate the image by cropping off unneeded space, changing the tint, brightness, and layout orientation.
Image generation is one of the digital image processing techniques that involves converting an image into some sort of ordered layout. For example, a scanner may pick up an image by creating a reflection. Digitization takes that reflection and attempts to arrange it into a series of pixels. Some forms of digitization make this arrangement by looking for variations in the amount of light recorded from the original image.
Enhancement is a broad category of digital image processing techniques that manipulate a digitized image. Computer programs may allow users to duplicate and change scanned images. For example, a color photograph can be converted to black and white. Likewise, parts of an image can be sliced and transposed into another.
Common techniques related to image enhancement include changing an image's tint. Some of the more common tint enhancements are related to primary colors, such as red, green, blue and yellow. A dull or faded image can be made brighter, which may eliminate some image or background imperfections. Contrast may be increased or decreased according to the amount of detail that needs to be shown.
Digital image processing techniques can also include restoration. Some scanned images may pick up tears or lines. Noise, which may show up as random dots or streaks, can be eliminated through replacement techniques. Replicas of the average recorded scan line replace defective or missing pixels.
Restoration may also involve the use of digital filtering. This is one of the digital image processing techniques that are used to eliminate dots or image spots. Any pixel that falls outside of an average range of values is typically eliminated when filtering is used. Pixels that fall outside the average range will usually show up as dark or lighter spots on the image.