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Guided By: Presented By: Prof. V. P. Sawalkar Rushikesh A. Welkar Alpha Compositing Computer Technology * Late Purushottam Hari (Ganesh) Patil Shikshan Sanstha’s Mauli Group of Institutions’, College of Engineering & Technology, Shegaon. 444002 Department of Computer Science & Engineering.

Alpha compositing computer technology

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Page 1: Alpha compositing computer technology

Guided By: Presented By:Prof. V. P. Sawalkar Rushikesh A. Welkar

Alpha Compositing Computer

Technology

*Late Purushottam Hari (Ganesh) Patil Shikshan Sanstha’s

Mauli Group of Institutions’,College of Engineering & Technology, Shegaon. 444002

Department of Computer Science & Engineering.

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ContentsIntroduction

Literature ReviewPropose System

What is alpha? What is alpha compositing? What is alpha Channel? TransparencyTechnical Aspect

Advantages & DisadvantagesConclusionReferences

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INTRODUCTION Alpha compositing is the process of combining an

image with a background to create the appearance of partial transparency.

In this techniques performs pixel by pixel blending of source and background color of images.

It's a way of mixing the colors of two images together to form a resultant image.

Pixels are the small elements of the images. In which each pixels data that is reserved transparency information of 32 bit.

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Literature Review In existing techniques i.e. Image stitching is techniques

in which Combine two or more overlapping images to make one larger image.

Example

Img1 img2 img3

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After overlapping 3 images

Resultant images

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What is alpha??

Alpha means transparency

The alpha idea been used to composite billions of pixels (if not more) to create images for print, video, film, and probably every other application of computer graphics.

The alpha values for an image are sometimes referred to collectively as the "alpha channel" of an image.

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What is alpha compositing?

Alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency of final image.

Compositing is the process by which graphical objects are combined.

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Working of alpha compositing

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Alpha channelThe alpha channel is a color component that

represents the degree of transparency or opacity of a color.

The alpha channel is typically represented by the letter α i.e.(alpha).

value of alpha

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Transparency The degree foreground color translucency may range

fromCompletely transparent to completely opaque. A value of 1 is completely solid and a value of 0 is

completely transparent.

The five rectangles have different alpha values of 0.1, 0.3, 0.5, 0.7 and 0.9 in order, from left to right as shown in fig.1.Fig1:

* Fig1: Five Green rectangles as foreground and common Red background

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According to above figure, we can see that when we give alpha value of 0.1 image is almost transparent and we cannot see foreground image (Green colour) and background (Red colour)

α*fgcolor+ (1- α) *bgcolor Where fgcoloris the colour of the rectangle and

bgcolor is the colour of the background. One can see that

0.1*green+(1-0.1) * red green(10%)+(90%red) if a=1, none of the background will be seen, and if

a=0 none of the rectangle will be visible.

Example

bgcolor= redfgcolor= green

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Technical AspectAlpha compositing is based on the idea of pre-

multiplication. If an alpha channel is used in an image, it is common to also multiply the color by the alpha value, to save on additional multiplications during compositing.

In pre-multiplication process, we store a color's components (typically red, green, and blue) already multiplied by alpha compositing.

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AdvantagesEasy to use

Easy to understandPre-multiplicationimage qualityTransparency

Disadvantages

Image limitationOverlapping of background imagesResize single image

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Conclusio

n Alpha compositing is technique in which we can combine two images and display it as a single image, in which we resize one image and pixels of that image will be overlapping pixels of our background image.

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References[1] http://home.comcast.net/~tom_forsyth/blog.wiki.html#Premultiplied alpha

[2] Compositing Digital Images Thomas Porter and Tom Duff, Computer Graphics Volume 18, Number 3, July 1984.

[3] Porter, T. Duff, SIGGRAPH '84, "Compositing Digital Images", Conference 3. [Blinn94] Blinn, James F,"Compositing, Part 1: Theory", IEEE Computer Graphics and Applications, September 1994.

[4] Porter, Thomas, and Duff, Tom, Compositing Digital Images, Computer Graphics, Vol 18, No 3, Jul 1984, 253-.SIGGRAPH’84.

[5] Smith, Alvy Ray, Color Gamut Transform Pairs, Computer Graphics, Vol 12, No 3, Jul 1984, 12-19.SIGGRAPH’78 Conference Proceedings

[6] Smith, Alvy Ray, Analysis of the Color-Difference Technique, Tech Memo 30, Computer Division, Lucasfilm Ltd.,Mar 1982.

[7] Smith, Alvy Ray, Math of Mattings, Tech Memo 32, Computer Division, Lucasfilm Ltd, Apr 1982. Reissue of techmemo of Dec 30, 1980.

[8] Vlahos, Petro, Composite Color Photography, US Patent 3,158,477, Nov 24, 1964. The classic color-difference bluescreen compositing technique.

[9] Principles of Color Technology 2nd Edition Billmeyer and Saltzman, John Wiley and Sons, 198

[10] Thomas Porter and Tom Duff, Compositing Digital Images, Computer Graphics

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Thank You !!!!!!