Showing papers on "Histogram equalization published in 1984"

The principles and methods of histogram modification adapted for visual perception

Abstract: Digital image histogram modification using a discrete raster and quantized gray levels is described. The histogram of an original picture is labeled pi and is first processed toward an aim histogram p′j. The gray level transformation and resulting histogram qk′ can be decided by Eqs. (2) and (3). The effect of histogram modification is explained by a theorem. In accordance with the visual character of the eyes, an appropriate aim histogram p′j is selected. If pi is constant, p′j may be represented by a beta distribution which can be varied by altering the parameters α and β. The optimum quantization gray levels for different visual models are determined. The histogram pi is changed by an order-preserving and layer-preserving gray level transform which has layers at the optimum quantization levels. This may be a simpler and more effective way of histogram modification. Finally, the concept of apparent entropy of an image is introduced and an approximation method of calculation of apparent entropy is suggested.

The Role Of An Image Processing Realtime Digital Disk In A PACS System

Abstract: This paper describes the application of a Realtime Digital Disk (RTDD) with processing capabilities and the increased functionality the RTDD brings to a PACS system. While the display and acquisition of images at 30 frames per second is the obvious advantage of the RTDD in PACS, the image processing and image enhancing functions make its use more effective. Realtime presentations include window and level of greater than 8 bit images, intensity transformation of 8 bit images, shape table and tiling presentation, and subsampling. Movie loop and three dimensional reconstruction sequences are viewed in realtime. Edge enhancement, smoothing, interpolated zoom, unsharp masking and other convolution filtering are near realtime presentations. Compression and decompression, histogram equalization and other transforms are performed in just a few frame times.

An Evaluation Of Digital Processing Capabilities For Improving Detection Of Low Contrast Round Objects In A Radiography By Contrast Detail Diagrams

Abstract: In this evaluation contrast-detail diagrams were used to measure the effects on observer performance of several image processing algorithms such as edge enhancement, smoothing and histogram equalization. The observer task was the detection of disk images in a uniform background. A new digital system, DigiRad System One, was used to digitize and postprocess images of a "Rose-Burger" contrast phantom. Results show that detectability of low contrast objects may increase for images taken with standard film/screen combinations. Anticipated changes on the System One may enhance its capabilities significantly.