Showing papers on "Alpha compositing published in 1994"

Method and apparatus for extracting and treating digital images for seamless compositing

Abstract: An image processing system for extracting and treating a digitized color subject image for seamless compositing against an arbitrary background includes the generation of a final control image from the image of a subject in front of a screen consisting of a range of colors. A sample of the background screen is captured and analyzed using filter kernels to determine a range of red, green and blue values which are stored in separate histograms. A first control image is generated by comparing mean histogram data with the subject image. A final control image is generated by dividing the first control image into separate background, foreground and fringe regions. A treated subject image is generated by leaking color from the local background region into the fringe regions of the subject image using filter kernels. The treated image is suitable for compositing against an arbitrary background image. The composite image may be touched up by using a software brush which on each pass of the brush expands the background region by eliminating immediately adjacent fringe pixels, causes other nearby fringe pixels to increase in translucence, and allows the boundary of the fringe region to encroach on the foreground region. Simultaneously, the brush may also cause fringe pixels to absorb some of the color of neighboring foreground pixels.

Compositing. 1. Theory

Abstract: Associating a pixel's color with its opacity is the basis for a compositing function that is simple, elegant, and general. However, there are more reasons than mere prettiness to store pixels this way. One of the most important anti-aliening tools in computer graphics comes from a generalization of the simple act of storing a pixel into a frame buffer. Several people simultaneously discovered the usefulness of this operation, so it goes by several names: matting, image compositing, alpha blending, overlaying, or lerping. It was most completely codified in a previous paper by Porter and Duff (1984), where they call it the over operator. The author shows a new way to derive the over operator and describes some implementation details that he has found useful. >

Image composition method and apparatus for developing, storing and reproducing image data using absorption, reflection and transmission properties of images to be combined

Abstract: A method and apparatus for implementing a new imaging and image composition system based on the real world metaphor of surface absorption, reflection, and transmission where many layers of translucent and opaque objects are composed into a final image for output to a video display. The algorithms are a substitution for both "Painter's algorithm" (the image composition technique traditionally used in computer graphic systems) and the alpha blending algorithms presently used in the computer and television industries for video special effects such as cross-fades between images, transparency, and color keying. In contrast to the prior art "colored pixel" algorithms, this system is based on a light propagation metaphor that uses virtual light source illumination and the absorption, reflection, and transmission properties of the objects in the image to create the final screen image. Thus, instead of representing each picture element (pixel) by color components specified by a chosen color model (e.g., RGB, YUV, Lab, HSV, YIQ, HLS, CMY, CMYK, etc.), the pixels in the subject system are represented by six explicit transformation components (r 1 , r 2 , r 3 , t 1 , t 2 , t 3 ) and three implicit transformation components (a 1 , a 2 , a 3 ), wherein a, r and t refer to absorption, reflection and transmission, respectively, and the subscripts 1, 2 and 3 refer to the components of the chosen color model.

The Inventor Toolmaker: Extending Open Inventor, Release 2

Abstract: From the Publisher: for graphics programmers. OpenGL is a powerful software interface for graphics hardware that allows graphics programmers to produce high- quality color images of 3D objects. The functions in the OpenGL library enable programmers to build geometric models, view models interactively in 3D space, control color and lighting, manipulate pixels, and perform such tasks as alpha blending, anti-aliasing, creating atmospheric effects, and texture mapping. Open Inventor is an object-oriented 3D toolkit built on OpenGL that provides a 3D scene database, a built-in event model for user interaction, and the ability to print objects and exchange data with other graphics formats. The OpenGL Technical Library provides tutorial and reference books for OpenGL and Open Inventor. The library enables programmers to gain a practical understanding of these important software standards and shows how to unlock their full potential.

Context sensitive color quantization system and method

Abstract: A system and method usable in producing a display image limited to a lesser number of colors from an input image having a greater number of colors. The invention is particularly useful in a computer system utilizing a video monitor capable of simultaneously displaying a selected number of colors stored in a lookup table. The system and method receive data representative of respective colors at a multiplicity of individual pixels in the input image. This input image data is then temporarily stored in an input buffer. An appropriate processor receives the input image data and performs image quantization thereon. Specifically, the processor first determines the selected colors to be included in the display image. Next, the processor determines which of the selected colors respectively correspond to individual pixels of the display image. Unlike the prior art, image quantization algorithms of the present invention selectively account for perceptive blending of colors appearing in the input image in determining the optimum display image. In other words, if individual colors appear in the input image in such a manner that a viewer would perceive a blended color, the invention will tend to display the blended color rather than the individual colors.