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Topic: Alpha compositing

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	Rendering model (SVG 1.2)
		Graphics elements are composited onto the elements already rendered on the canvas based on an extended Porter-Duff compositing model, in which the resulting color and opacity at any given pixel on the canvas depend on the 'comp-op' specified.
		For groups containing compositing operators, the operation used to composite the group onto the canvas is the comp-op property of the container element itself.
		In effect, the destination input to the compositing operations for the complex group's children is the original contents of the buffer, rather than the current buffer for the complex group.
	www.w3.org /TR/SVG12/rendering.html (5223 words)

	Image Compositing
		Compositing is the name given to the process of combining multiple images as overlapping layers producing a single output image.
		An early use of compositing was in the cartoon industry where each artist draws one aspect of the scene as a layer, the multiple layers from each artist are combined to form the current frame.
		With an alpha channel indicating opaque (1, white) or transparent (0, fl), layers can now be added together from the background to the foreground such that those parts of a layer that are transparent don't affect anything behind them and those parts that are opaque write over anything behind them.
	local.wasp.uwa.edu.au /~pbourke/colour/composite (748 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency.
		If an alpha channel is used in an image, it is common to also multiply the color by the alpha value, in order to save on additional multiplications during the compositing process.
		The alpha component may be used to blend to red, green and blue components equally, as in 32-bit RGBA, or, alternatively, there may be three alpha values specified corresponding to each of the primary colors for spectral color filtering.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Alpha_compositing (625 words)

	Beginning Java 2 - JDK 1.3 Version Part 6 - Alpha Compositing
		The alpha value is multiplied by each of the color components to modify the contribution of each color component to the visual appearance of the pixel.
		There are several alpha compositing rules as we shall see, but they each determine the fraction of the source image components and the fraction of the destination image components that contribute to the components of the result.
		Since an image with no alpha channel has an alpha component that is assumed to be 1.0, the alpha value that you specify in the call to getInstance() becomes the alpha value for all the pixels in the source.
	tutorials.beginners.co.uk /read/id/111/p/1 (1380 words)

	Digital compositing - Wikipedia, the free encyclopedia
		The basic operation used is known as 'alpha blending', where an opacity value, 'α' is used to control the proportions of two input pixel values that end up a single output pixel.
		A monochrome raster image where the pixel values are to be interpreted as alpha values is known as a matte.
		It is possible for a compositing artist to compensate for the effects of compositing in non-linear space.
	en.wikipedia.org /wiki/Digital_compositing (437 words)

	Alpha Compositing
		The alpha value is multiplied by each of the color components to modify the contribution of each color component to the visual appearance of the pixel.
		The alpha value for a pixel in an image can vary from a minimum of 0.0, meaning completely transparent and therefore invisible since all the color components will be 0, to a maximum of 1.0, meaning completely opaque.
		There are several alpha compositing rules as we shall see, but they each determine the fraction of the source image components and the fraction of the destination image components that contribute to the components of the result.
	www.javable.com /docs/books/wroxpress/beg_java2/sample/36681706.htm (2465 words)

	RMagick - Alpha Compositing - Part I
		In image processing, alpha compositing is the blending of two images into a single image by combining the pixel data from each image according to a mathematical formula.
		As I explained earlier, the src-over composite operation produces a composite image by replacing the pixels in the destination image with the corresponding pixels in the source image.
		The transparent pixels in the source are also composited onto the destination, but since the source pixels outside the penguin are transparent (that is, 0% opaque) 100% of the destination pixel shows through.
	rmagick.rubyforge.org /src_over.html (1288 words)

	Java 2D Graphics, The Composite Interface and Transparency
		After the Composite is set in the Graphics2D context, it combines a shape, text, or an image being rendered with the colors that have already been rendered according to pre-defined rules.
		The alpha resulting from the compositing operation is stored in the destination if the destination has an alpha channel.
		alpha - the constant alpha to be multiplied with the alpha of the source.
	www.developer.com /tech/print.php/626361 (3535 words)

	Alpha Channels \| premultiplied, straight and uncorrelated
		In this case, when you use the alpha channel to unnecessarily extract the foreground from its fl background, you pull in gray around the edge, creating a matte line.
		To use such an alpha channel, one must emulate the behavior of a film optical printer — one must run the fl core matte as a holdback for the background, and then add the foreground as a burn-in, or a "DX" (a double exposure).
		Invert (~) the alpha channel and multiply (*) it by the background.
	www.digitalartform.com /alphaChannel.htm (679 words)

	A New Rendering Model for X
		For 16 bit images sometimes the alpha channel is embedded as one of four 4-bit components and sometimes the alpha channel is in a separate 8-bit image.
		Alpha compositing is easy to describe in a TrueColor environment, but more problematic in PseudoColor where there is no linear relation between pixel and color.
		Given that this alpha blending technique is only approximate and that sophisticated techniques are likely to be a performance problem in the near term, only the simple coverage model is currently planned.
	www.keithp.com /~keithp/talks/usenix2000/render.html (3352 words)

	IM v6 Examples -- Compose (Site not responding. Last check: 2007-11-07)
		Alpha Compositing is the technique of combining images, (with or without transparency, or alpha channels) together in some way.
		Alpha Composition in IM Alpha Composition is the process of merging two (or more) images together in various ways.
		Alpha composition is used in a lot of different places in ImageMagick, either directly, or indirectly as part of an image operators internal processing.
	www.cit.gu.edu.au /~anthony/graphics/imagick6/compose (8613 words)

	compositing (Site not responding. Last check: 2007-11-07)
		In a compositing situation, anti-aliasing has one undesirable side effect: The edge pixels of objects become blended with the background color.
		Alpha channel includes the necessary information for blending the image over a new background, as the next tutorial shows.
		The Targa image sequence, which was processed in the previous tutorial, includes alpha channel information and is suitable for use in various composition systems.
	www.phnet.fi /public/realsoft/postproc/compositing.html (2514 words)

	[No title] (Site not responding. Last check: 2007-11-07)
		Alpha is set to 0, which means that where there is no shadow, the alpha value of those pixels will be 0
		If the alpha (or red, or green, or blue, etc depending of the channel specified) value of a pixel in the foreground matte is 0, the pixel at the same position in the foreground image will not be drawn over the background (the foreground was stop by the stencil, thus the bg will be seen)
		If the value of a pixel in the foreground matte is greater than 0, than the pixel at the same position in the foreground will be drawn on top of the background with an opacity corresponding to the value in the foreground matte (1 is totally opaque).
	www.cgl.uwaterloo.ca /~fine328d/notes/Compositing.html (2037 words)

	Design and Implementation of the X Rendering Extension
		The Porter-Duff compositing model unifies the usual notion of translucency, where a pixel is entirely covered with a non-opaque value, with the notion of partial coverage, where a portion of the pixel is covered while the remaining portion is uncovered.
		At the heart of the Render extension lies a single request: all other rendering is defined in terms of the Composite request which performs the basic composite rendering operation described in Section 2.2.
		The destination quadrilateral forms an implicit alpha mask which may be used to smooth the edges of the transformed image.
	keithp.com /~keithp/talks/usenix2001/xrender (6877 words)

	Understand Compositing and Color extensions in SVG 1.2 in 30 minutes!
		Simple alpha compositing, like that found by default in SVG 1.1 and in GDI+ and many other graphics engines, composites each object onto the background image using a simplistic formula that has the effect of overlaying the object over the background.
		The alpha channel is used to indicate the coverage of the color at that pixel.
		Compositing functionality in Java 2D is generally performed in the manner described by this attribute.
	www.svgopen.org /2005/papers/abstractsvgopen (4846 words)

	Compositing
		Unfortunely, one of the difficult parts of compositing is to create a format that is usable in a variety of editing environments.
		Lightwave's alpha channel is an exellent way to do this even if making a "perfect alpha" is quite tricky.
		The problem with alpha channels is that when an image is rendered using motion blur, DOF or even anti-alias, whatever background information was used during the render, the edges will contain color portions of that because of the way that render passes are mixed together.
	www.ethereal3d.com /Tutorials/Compositing/Compositing.html (1271 words)

	Java 2 Platform SE v1.3.1: Class AlphaComposite
		class implements the basic alpha compositing rules for combining source and destination pixels to achieve blending and transparency effects with graphics and images.
		object with the specified rule and the constant alpha to multiply with the alpha of the source.
		- the constant alpha to be multiplied with the alpha of the source.
	java.sun.com /j2se/1.3/docs/api/java/awt/AlphaComposite.html (869 words)

	Alpha channel
		Although the whole Alpha channel technique is generally credited to Thomas Porter and Tom Duff back in 1984 while they where working on composition techniques for the Star Trek film "The Wrath of Khan".
		Because when you fade your bitmap to white, you are actually already compositing your image with a white background and this white background component will show through when the image is composited over another background image later.
		This is important to do when you use Photoshop to produce alpha images intended to be used as decals in A:M because otherwise, A:M will think the image is not premultiplied as is indicated in the TGA files by Photoshop.
	www.ypoart.com /tutorials/Alpha-about.htm (1569 words)

	Alpha compositing - Wikipedia, the free encyclopedia
		In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency.
		It is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a process called compositing.
		To store this matte information, the concept of an alpha channel was introduced by A.R.Smith in the late 1970s, and fully developed in the 1984 paper Compositing Digital Images, by Thomas Porter and Tom Duff.
	en.wikipedia.org /wiki/Alpha_compositing (570 words)

	Clipping, Masking and Compositing
		A clipping path can be thought of as a mask wherein those pixels outside the clipping path are fl with an alpha value of zero and those pixels inside the clipping path are white with an alpha value of one (with the possible exception of antialiasing along the edge of the silhouette).
		For a four-channel RGBA graphics object that is used as a mask, both the color channels and the alpha channel of the mask contribute to the masking operation.
		The alpha mask that is used to composite the current object into the background represents the product of the luminance of the color channels (see previous paragraph) and the alpha channel from the mask.
	www.w3.org /TR/2001/PR-SVG-20010719/masking.html (3152 words)

	IM v6 Examples -- Compose Tables
		That are use as a basic summary of these important alpha compositing methods.
		Note that there are a number of methods which are not listed in the ImageMagick manuals, which I display in these table, on the otherhand I do not display all the compose operators either.
		As some of compositing operators will modify the whole background (destination) image, including outside the overlaid area, or even if the source is completely transparent.
	www.cit.gu.edu.au /~anthony/graphics/imagick6/compose/tables (288 words)

	... in Java by Richard G Baldwin
		Figure 7 simply renders the ellipse according to the paint and composite properties previously established.
		Figure 12 shows the invocation of the setComposite() methods for the red, green, and blue ellipses respectively in the lower-left quadrant.
		Figure 13 shows that the red ellipse is opaque (alpha equals 1.0f).
	www.dickbaldwin.com /java/Java320.htm (3342 words)

	pippin.gimp.org - painting from code (Site not responding. Last check: 2007-11-07)
		Using a backing buffer, and redrawing the current path, does not allow variable alpha, variable line width could be written on top of cairo.
		Uses X11 directly, no alpha nor, antialiasing but is fast enough to provide for interactive drawing.
		Another thing that is needed is calibration of both coordinates, and pressure, pressure is probably best calibrated with live tuning of strokes after they have been created,.
	pippin.gimp.org /sputnik/pressure/old.html (229 words)

	AlphaComposite (Java 2 Platform SE v1.4.2)
		The rules implemented by this class are the set of Porter-Duff rules described in T. Porter and T. Duff, "Compositing Digital Images", SIGGRAPH 84, 253-259.
		The part of the source lying inside of the destination is composited onto the destination.
		The part of the destination lying inside of the source is composited over the source and replaces the destination.
	java.sun.com /j2se/1.4.2/docs/api/java/awt/AlphaComposite.html (1122 words)

	Antialiasing, images, and alpha compositing in Java 2D - Java World
		Here I blend a transformed copy of the infamous column photo over our old friend the green-filled shape in a technique known as alpha compositing.
		Alpha compositing blends colors from the rasters of two or more graphics objects.
		Alpha blending an image over an arbitrary 2D shape.
	www.javaworld.com /javaworld/jw-08-1998/jw-08-media.html?page=4 (960 words)

	PNG Support in Mozilla [OLD!]
		Classic Mozilla didn't do any compositing on its own; it left that to various platform-dependent API calls in the front ends, which is why it was limited to binary transparency.
		On top of that, Simon Fraser did the same for Macintosh, and as of 20 April 2000, 8-bit alpha blending was enabled on all three main platforms.
		That is, even though I understand the PNG code pretty well, the limitations that stand in the way of implementing full alpha transparency and of fixing the interlace bug all live elsewhere, and I simply don't have the time to try to understand those parts of the code.
	www.libpng.org /pub/png/pngmoz.html (1955 words)

	Help. Compositing / Glow / Alpha Channel Question - NewTek Discussions
		I have composited this in After Effects with a background of a building, trees and landscape.
		I attempted to bring the footage of the spacecraft into After Effects to composite it together.
		I have tried rendering out a separte alpha channel for the glow and putting it in After Effects, but (i dont' know how firstly) it doesn't seem to work.
	www.newtek.com /forums/showthread.php?t=16524 (578 words)

	The Java Boutique: Java Books: Beginning Java 2- JDK 1.3 Version - Page 30
		This allows the transparency to vary over the image, so some parts of the image could be opaque — with an alpha component of 1.0, and other parts may be more or less transparent, with alpha components for the pixels less than 1.0.
		The color components for each pixel in the source image and the corresponding pixels in the destination image will be multiplied by their alpha component — often this will be done once and for all ahead of time for an image to avoid all those multiplications each time you draw an image.
		argument in order to set the alpha compositing rule to be used when you draw in the graphics context.
	javaboutique.internet.com /resources/books/beginjava2/java2-6_1.html (874 words)

	The interface between Ghostscript and device drivers (Site not responding. Last check: 2007-11-07)
		Note that the compositor may have a different color space, color representation, or bit depth from the device to which it is compositing.
		Specifies whether alpha channel information should be returned as the first component, the last component, or not at all.
		Note that for devices that have no alpha capability, the returned alpha values will be all 1s.
	www.delorie.com /gnu/docs/ghostscript/Drivers.htm (8571 words)

	kaourantin.net: Some word on blend modes in Flash Player 8
		The main source was the SVG 1.2 draft spec which presents the algorithms working with premultiplied alpha color values which Flash needs.
		In addition we would have had to implement a JIT for compositing functions just to make it fast enough and that was frankly out of the scope for this release.
		If you used Flash in the past, the alpha color transform would be applied separately to each image instead of being applied to the whole stack of images taken together.
	www.kaourantin.net /2005/09/some-word-on-blend-modes-in-flash.html (1213 words)

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