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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.


Papers
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Proceedings ArticleDOI
01 Jan 2009
TL;DR: This article proposes a computationally efficient method of scene compositing using edge-prese rving filters such as bilateral filters and considers the High Dynamic Range Imaging (HDRI) problem.
Abstract: Compositing a scene from multiple images is of considerableinterest to graphics professionals. Typical compositing techniques involve estimation or explicit prepar ation of matte by an artist. In this article, we address the problem of automatic compositing of a scene from images o btained through variable exposure photography. We consider the High Dynamic Range Imaging (HDRI) problem an d review some of the existing approaches for directly generating a Low Dynamic Range (LDR) image from mul ti-exposure images. We propose a computationally efficient method of scene compositing using edge-prese rving filters such as bilateral filters. The key challenge is to composite the multi-exposure images in such a way so as t o preserve details in both brightly and poorly illuminated regions of the scene within the limited dynamicrange.

162 citations

Proceedings ArticleDOI
Aseem Agarwala1
29 Jul 2007
TL;DR: This paper shows how to perform gradient-domain compositing approximately by solving an O(p) linear system, where p is the total length of the seams between image regions in the composite; for typical cases, p is O(√n).
Abstract: We describe a hierarchical approach to improving the efficiency of gradient-domain compositing, a technique that constructs seamless composites by combining the gradients of images into a vector field that is then integrated to form a composite. While gradient-domain compositing is powerful and widely used, it suffers from poor scalability. Computing an n pixel composite requires solving a linear system with n variables; solving such a large system quickly overwhelms the main memory of a standard computer when performed for multi-megapixel composites, which are common in practice. In this paper we show how to perform gradient-domain compositing approximately by solving an O(p) linear system, where p is the total length of the seams between image regions in the composite; for typical cases, p is O(√n). We achieve this reduction by transforming the problem into a space where much of the solution is smooth, and then utilize the pattern of this smoothness to adaptively subdivide the problem domain using quadtrees. We demonstrate the merits of our approach by performing panoramic stitching and image region copy-and-paste in significantly reduced time and memory while achieving visually identical results.

144 citations

Patent
15 Feb 1991
TL;DR: In this article, the alpha channel comprises either a sub-pixel mask associated with each pixel which indicates the amount and subpixel regions of coverage or a single value indicative of the percentage of coverage of a pixel.
Abstract: A scan conversion process is performed on a polygon using a single pass technique. The pixels which comprise the edges and vertices of the polygon are first determined from the vertices which define the polygon. The alpha channel comprises either a sub-pixel mask associated with each pixel which indicates the amount and sub-pixel regions of coverage or a single value indicative of the percentage of coverage of a pixel. Furthermore, a z value indicative of the depth of each pixel is maintained. The pixels between the edge pixels of the polygon are then turned on, thereby filling the polygon. The pixels which comprise the polygon are then composited with the background pixels on a per pixel basis. The depth value of each pixel of the polygon (the z value) is used to determine the compositing equations to be used to composite each pixel of the polygon to the background. The compositing equations update the color of the pixel, the z buffer value of the background pixel and the sub-pixel mask to reflect the addition of information from the compositing of the pixel of the polygon into the background pixel. Through this method high quality anti-aliased polygons may be rendered without performing the time consuming process of sorting the polygons in depth order prior to compositing.

140 citations

Patent
27 Apr 1995
TL;DR: In this paper, a frame buffer dynamic random access memory (FBRAM) is proposed that enables accelerated rendering of Z-buffered graphics primitives by converting read-modify-write transactions such as buffer compare and RBG alpha blending into a write only operation.
Abstract: A frame buffer dynamic random access memory (FBRAM) is disclosed that enables accelerated rendering of Z-buffered graphics primitives. The FBRAM converts read-modify-write transactions such as Z-buffer compare and RBG alpha blending into a write only operation. The FBRAM also implements two levels of internal pixel caches, and a four-way interleaved frame buffer.

130 citations

Patent
Kevin John Moore1
20 Feb 2004
TL;DR: In this paper, the authors proposed a pixel compositing algorithm for rendering an object-based image one pixel at a time in scanline order, where the first pixel is generated by a set of compositing messages between adjacent edges of one or two objects.
Abstract: Apparatus 20 is disclosed for rendering an object-based image one pixel at a time in scanline order. The apparatus 20 comprises an optimisation module 550 for generating a set of compositing messages during a first pixel in a run of pixels between adjacent edges of one or two objects, and for generating a reduced set of compositing messages from the set during subsequent pixels in the run of pixels. The apparatus 20 further comprises a pixel compositing module 700 which in addition to compositing the first pixel in the run of pixels also stores a result or partial result of the compositing of the first pixel. The pixel compositing module 700 utilises the reduced set of compositing messages and the stored result or partial result to composite pixels in the run subsequent to the first pixel.

124 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
20219
20208
201913
201821
201723