The space which black and white or color images require to be stored introduces one of the biggest problems in the field of Graphic Arts. A solution to this problem is offered through the use of software programs that compress the data of a scanned image. Compressing images without any consideration can create other problems. These problems arise because each image has a different structure . It is possible to classify images into three main categories using as a criterion the frequencies the images contain. The first category includes images that contain high frequencies -a lot of detail and very small uniform areas. The second category includes images with fewer frequencies - less detail and larger uniform areas. The third includes images with low frequencies - just a few (or no) details and large uniform areas. The main goal of this study was to set compression ratio standards according to the structure of the images. A software program that does data compression was used. Three 35 mm slides were used as well. The slides have been chosen carefully so that the main topics were composed of frequencies in distinct ranges. All of the images were scanned at 300 pixels per inch. Then all of the images were compressed at three specific compression ratios ( 5:1 , 8:1 , and 14:1) and then printed. Output size was 5x7 inches, the resolution was 256 dpi, and halftones were 150 lines per inch (LPI). A group of forty people (twenty professionals and twenty novices) compared the control image ( non compressed image) with each of the compressed images. The Chi square test was used to analyze the data. The results indicate that it is acceptable to compress images with low detail (like the image Shaving Material) and medium detail (like the image Three Amigos) up to fourteen to one (14:1), because any loss of data is apparently not detectable by the human eye. On the other hand, images which contain a lot of detail (like the image Doll), can not be compressed using the above (14:1) compression ratio without any loss of information being detected. However these images can be compressed up to 8:1 , and any loss of detail up to this compression ratio will not be detected.
Library of Congress Subject Headings
Data compression (Computer science); Color computer graphics; Image processing
Department, Program, or Center
School of Print Media (CIAS)
Koutsogiannis, Vassilis, "A Study of color image data compression" (1992). Thesis. Rochester Institute of Technology. Accessed from
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