Conversion from 16-bits to Standard 8-bits format



next up previous contents
Next: Reconstruction software Up: No Title Previous: Radial grey level

Conversion from 16-bits to Standard 8-bits format

 

In addition to our own software for controlling the CCD camera, two others were available. Photometrics delivered their own software together with the camera. Most of the image analysis was made with a version of IP Lab from Signal Analytics Corporation[29]. IP Lab supported the Photometrics Series 200 Camera System and had many useful image processing possibilities. Both softwares have their own special 16-bits storage format. Together with Finn Boger conversion programs for Apollo and Hewlett Packard work stations were written. The conversion programs made it possible to convert from all three formats to the 8-bits standard format used at the Cooperative Phenomena.

In all the storage formats the size of the picture is saved in the heading. By using this information and finding the maximum and minimum values in the picture, the 12-bits values were normalized to 8-bits resolution using the formula V_new & = & 255 V_old-V_minV_max-V_min \;.   Here and are respectively the maximum and minimum pixel values in the original picture. Each pixel value in the original picture, is mapped to a new value, , between 0 and 255. As an option, the maximum-, , and the minimum-, , values could be specified by the user. The original values larger than the were normalized to 255 in the new picture. Similarly the values smaller than were normalized to 0. The intermediate values were normalized according to equation gif. This made it possible to enhance the contrast in the original picture.



Thomas Walmann
Fri Apr 7 16:34:05 METDST 1995