Alpha compositing

About: Alpha compositing is a research topic. Over the lifetime, 482 publications have been published within this topic receiving 11035 citations. The topic is also known as: alpha blend & alpha channel.

Compositing 3-D rendered images

Abstract: The complexity of anti-aliased 3-D rendering systems can be controlled by using a tool-building approach like that of the UNIX™ text-processing tools. Such an approach requires a simple picture representation amenable to anti-aliasing that all rendering programs can produce, a compositing algorithm for that representation and a command language to piece together scenes. This paper advocates a representation that combines Porter and Duff's compositing algebra with a Z-buffer to provide simple anti-aliased 3-D compositing.

Multiblending: displaying overlapping windows simultaneously without the drawbacks of alpha blending

Abstract: Alpha blending allows the simultaneous display of overlapping windows-such as palette windows in visual workspaces. Although alpha blending has been used in some applications, such as games, it has not been widely adopted. One reason for the limited acceptance is that in many scenarios, alpha blending compromises the readability of content. We introduce a new blending mechanism called multiblending that uses a vector of blending weights, one for each class of features, rather than a single transparency value. Multiblending can in most cases be automatically optimized to preserve the most relevant features of both the palette and the background window. We present the results of a user study in which multiblended palettes provided higher recognizability of both the background and the palette than the best participating version of alpha blending.

SLIC: scheduled linear image compositing for parallel volume rendering

Abstract: Parallel volume rendering offers a feasible solution to the large data visualization problem by distributing both the data and rendering calculations among multiple computers connected by a network. In sort-last parallel volume rendering, each processor generates an image of its assigned subvolume, which is blended together with other images to derive the final image. Improving the efficiency of this compositing step, which requires interprocesssor communication, is the key to scalable, interactive rendering. The recent trend of using hardware-accelerated volume rendering demands further acceleration of the image compositing step. We present a new optimized parallel image compositing algorithm and its performance on a PC cluster. Our test results show that this new algorithm offers significant savings over previous algorithms in both communication and compositing costs. On a 64-node PC cluster with a 100BaseT network interconnect, we can achieve interactive rendering rates for images at resolutions up to 1024x1024 pixels at several frames per second.

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.

Alpha channel estimation in high resolution images and image sequences

Abstract: For motion picture special effects, it is often necessary to take a source image of an actor, segment the actor from the unwanted background, and then composite over a new background. The standard approach requires the unwanted background to be a blue screen. While this technique is capable of handling areas where the foreground blends into the background, the physical requirements present many practical problems. This paper presents an algorithm that requires minimal human interaction to segment motion picture resolution images and image sequences. We show that it can be used not only to segment badly lit or noisy blue screen images, but also to segment actors where the background is more varied.