Showing papers on "Histogram equalization published in 1980"

Rapid Texture Identification

Abstract: A method is presented for classifying each pixel of a textured image, and thus for segmenting the scene. The "texture energy" approach requires only a few convolutions with small (typically 5x5) integer coefficient masks, followed by a moving-window absolute average operation. Normalization by the local mean and standard deviation eliminates the need for histogram equalization. Rotation-invariance can also be achieved by using averages of the texture energy features. The convolution masks are separable, and can be implemented with 1-dimensional (vertical and horizontal) or multipass 3x3 convolutions. Special techniques permit rapid processing on general-purpose digital computers.

Real time histogram modification system

Abstract: An iterative real time histogram modification system for use in image processing, such as image contrast enhancement of for example scenes, radiograms and thermograms. In the described system input analogue video signals to be modified are digitized and applied to an encoding module including a code RAM which compresses the input grey levels into a lesser number of output grey levels in accordance with a recoding strategy applied to the code RAM. The recoding strategy is determined iteratively using a predetermined scene adaptive operator. This is done by forming a histogram of the pixels in the respective output grey levels. Thereafter the count in each grey level is compared with a predetermined population figure for that grey level and if the difference between the count and population figure is outside an acceptable range, termed a window, then the recoding strategy to be used during the next frame of the input signals is altered so that the number of input grey levels compressed into the particular output grey level is adjusted appropriately. The recoding strategy may be applied to a local area of the frame, which area is selected at will, or to the entire frame in which case the histogram is formed from a subset of all the pixels. The scene adaptive operators include histogram equalization, Gaussian distribution, hyperbolic and exponential. By using a suitably programmed microprocessor different scene adaptive operators may be selected at will and a "zoom" facility may be provided in which the size of the local area is varied and corresponding changes are made to the window and set of population figures.

Forward Looking Infrared (FLIR) Image Enhancement For The Automatic Target Cuer System

Abstract: The goal of FLIR image enhancement is to obtain a good quality display by compressing the global scene dynamic range while enhancing the local area contrast. This paper presents the investigation and the implementation of six candidates for FLIR image enhancement and shows some experimental results. The six enhancement candidates are: (1) variable threshold zonal filtering, (2) statistical differencing operator, (3) unsharp masking, (4) prototype automatic target screener technique, (5) constant variance, and (6) histogram equalization. All the enhancement techniques make use of the local nonstationary mean, the local variance, or both, to achieve edge enhancement or contrast stretching in local regions. The local nonstationary mean and the local variance, in each case, are computed by a two-dimension rolling window averaging processor. Finally, an experiment based on subjective criteria to judge the enhanced image quality was conducted. The results showed that the variable threshold zonal filter, prototype automatic target screener, and unsharp masking methods were the superior techniques.

Polychromatic processing technique for color image transparencies.

Abstract: A technique of spatial encoding color photographic image in a black and white tran-sparency for coherent polychromatic processing is presented The applications of this technique to color image signal detection, restoration of color blurred images, and color image addition and subtraction are provided We note that this polychromatic processing technique is capable of processing color images similar to monochromatic coherent pro-cessing technique Although there is a disadvantage of this technique, it requires an en-coding step for image processing, however this technique may open a new dimension in color image processing We also note that the application of this technique is not res-tricted only to color images, it may apply to some problems in gray level transparencies

TV‐rate histogram equalization processor for the electron microscope

Abstract: A fast (NTSC TV‐rate), low cost, simple histogram equalization processor is described. In this apparatus, the histogram equalization processing is carried out by the table look‐up method at TV‐rate. The characteristics of the processor, and its applications to the real time and on‐line processing of weak contrast images from the Ultra‐High Voltage Electron Microscope (Osaka University) are described. With this apparatus, equilevel processing, level compression, and level slicing may also be easily carried out.