Digital Image Processing

Digital Image Processing

Copyright: © 2018 |Pages: 35
DOI: 10.4018/978-1-5225-3270-5.ch002


The first two sections of this chapter introduce the motivation and fundamental theoretical perceptions towards DIP and encoding formats. The RGB system color and the visual quality improvement (by increasing the contrast with histograms enhancement techniques) are emphasized in section “Digital Image Enhancement” and “Elementary Operations With Digital Images”, respectively. Spatial filtering and masks are analyzed in section “Filtering”, which some Java code has been included for illustrative purposes. The next section explains how to save a myGeoffice© generated image to your hard disk and provides examples of image processing. Section “JHLABS® Image Editor” and “LightBox® Image Editor” depicts JHLabs®, a Web editor built on Swing technology, and Lightbox® of myGeoffice©. Its filtering capabilities are presented in the last section.
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Concepts Of Digital Image Processing

Digital images can be obtained through scanners, digital cameras and remote sensors. A scanner is an optical reading device that converts images, photos, illustrations and texts into a digital format that can be manipulated by a computer. The most common scanner is the flatbed, which is similar to a photocopier. Other types are barcode readers and hand and drum scanners. In an operational context, all scanners are based on the principle of light reactance, which consists of positioning the image so that the intensive light (generated by fluorescent or cathode-cold type lamp) hits it. A sensitive sensor captures this reflected radiance thereby forming a digital image. Currently, the most commonly used sensors are as follows (Felgueiras & Negreiros, 2008):

  • Photo Multiplier Tube (PMT): The standard hardware for drum scanners in the current printing industry for high-quality prints. This scanning device is placed in a glass cylinder that rotates at high speed around the PMT sensor, dividing the reflected light into three beams (which passes through filters) and generating the scanned image.

  • Charge Coupled Device (CCD): Used in almost all domestic scanners (fax, digital cameras), it stands out for its good quality and low price. This type of sensor converts the reflected light into electrical signals that in turn are converted into bits by an analogue-to-digital converter (ADC) circuit.

  • Contact Image Sensor (CIS): Uses a series of red, blue and green LEDs to produce white light. This allows greater energy savings. However, the image quality is not as good as compared to CCDs.

The scanning process enables analog signals to be converted into quantized levels of digital information. Naturally, the higher the number of digital levels, the better the representation of the analog signal becomes. Yet, one need a larger number of bits to represent the image and, hereafter, more (virtual and real) RAM memory to store that image is required.

With regard to digital cameras resolution, Table 1 relates the standard sizes of a digital image (columns versus rows) to the quantity of megapixels incorporated in the conventional digital camera.

Table 1.
For reference, remote sensors are Earth mapping devices placed on airplanes and satellites that enable imaging over large distances using three types of technologies: Thematic mapping, infrared and CCD sensors
SizeMegapixelsRecommended Use
640x4800.3Only for Internet
1024x7680.78Printings up to 9x13
1289x9601.2Printings up to 10x15
1600x12002.0Printings up to 13x18
2048x15363.1Printings up to 20x30

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