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5-1-3 Still Image Processing

Still image processing is the process of handling images that do not move. The basic mechanisms of image representation include the color representation method and image quality.

• • Color representation method
  This method uses the three primary colors of light (RGB) and the three primary colors of color (CMY). Generally, RGB is used in the color representation of the display, and CMY is used in the color representation of the printer. However, it is common to use the four colors of CMYK by adding black (Key) to the three primary colors of color.
• • Image quality
  This is represented by resolution and gradation. Resolution represents the density of the pixels (i.e., dots) configuring an image in the number (dpi (dots per inch)) of pixels (i.e., dots). Gradation represents the stage of the color that can be represented in each pixel. · 1 question

The typical formats (i.e., standards) of a still image file are as follows:

• • BMP (Bit MaP)
  It is a format that represents the characters and images as a set of dots. A flaw that exists is that the amount of information generally increases more than in other formats.
  • • TIFF (Tagged Image File Format)
    It is a format that enables handling of bit map images of various formats through the addition of tags (i.e., identifiers).
• • JPEG (Joint Photographic Experts Group)
  

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It is an international standard that supports full color and is defined by JPEG, an institution of ISO. It is a still image compression and decompression format that enables adjustment of the image quality and data amount by regulating the amount of compression. Because of an extremely high compression rate, it is used more frequently than other still image file formats. The compression formats of JPEG include lossless compression in which the original data is completely recovered and lossy compression in which the original data is not completely recovered. However, the lossy compression format is generally used. · 1 question

• • GIF (Graphic Interchange Format)
  It is a still image compression and decompression format that supports 256 colors. Although it is a lossless compression format, the amount of data is comparatively less, and it is also used in image processing on the WWW.
• • PNG (Portable Network Graphics)
  It is a still image compression and decompression format that supports full color and is an expansion of GIF. It is a lossless compression format, and the amount of data is more than JPEG.
• • Exif (Exchangeable Image File Format)
  It is a format that additional information (i.e., meta data), such as the photography time, is attached and saved in the image data taken by a digital camera.