4-Image

4-Image - Feature Based Image Metamorphosis, Beier and...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Image Compositing and Morphing Jason Lawrence CS 4810: Graphics Feature Based Image Metamorphosis , Beier and Neely 1992 Acknowledgement: slides by Misha Kazhdan, Allison Klein, Tom Funkhouser, Adam Finkelstein and David Dobkin
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Outline • Image Compositing o Blue-screen mattes o Alpha channel o Porter-Duff compositing algebra • Image Morphing
Background image of page 2
Image Compositing Separate an image into “elements” o Render independently o Composite together Applications o Cel animation o Chroma-keying o Blue-screen matting Bill makes ends meet by going into flm
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Blue-Screen Matting Composite foreground and background images o Create background image o Create foreground image with blue background o Insert non-blue foreground pixels into background
Background image of page 4
Blue-Screen Matting Composite foreground and background images o Create background image o Create foreground image with blue background o Insert non-blue foreground pixels into background Problem: lack of partial coverage results in a haloing effect along the boundary!
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Encodes pixel coverage information o α = 0: no coverage (or transparent) o α = 1: full coverage (or opaque) o 0 < α < 1: partial coverage (or semi-transparent) Single Pixel Example: α = 0.3 Alpha Channel Partial Coverage Semi- Transparent or
Background image of page 6
Compositing with Alpha Controls the linear interpolation of foreground and background pixels when elements are composited. α = 1 0 < α < 1 α = 0 0 < α < 1
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Pixels with Alpha • Alpha channel convention: o (r, g, b, α ) represents a pixel that is α covered by the color C = (r* α , g* α , b* α ) »Color components are pre-multiplied by α »Can display (r,g,b) values directly • What is the meaning of the following? o (0, 1, 0, 1) = ? o (0, 1/2, 0, 1) = ? o (0, 1/2, 0, 1/2) = ? o (0, 1/2, 0, 0) = ?
Background image of page 8
Pixels with Alpha • Alpha channel convention: o (r, g, b, α ) represents a pixel that is α covered by the color C = (r* α , g* α , b* α ) »Color components are pre-multiplied by α »Can display (r,g,b) values directly • What is the meaning of the following? o (0, 1, 0, 1) = Full green, full coverage o (0, 1/2, 0, 1) = ?
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 48

4-Image - Feature Based Image Metamorphosis, Beier and...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online