lec7 - 1 CSE152 Spring 2011 Intro Computer Vision...

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Unformatted text preview: 1 CSE152, Spring 2011 Intro Computer Vision Introduction to Computer Vision CSE 152 Lecture 7` CSE152, Spring 2011 Intro Computer Vision slide from T. Darrel CSE152, Spring 2011 Intro Computer Vision The principle of trichromacy • Experimental facts: – Three primaries will work for most people if we allow subtractive matching • Exceptional people can match with two or only one primary. • This could be caused by a variety of deficiencies. – Most people make the same matches. • There are some anomalous trichromats, who use three primaries but make different combinations to match. CSE152, Spring 2011 Intro Computer Vision Color Matching Functions CSE152, Spring 2011 Intro Computer Vision Color spaces • Linear color spaces describe colors as linear combinations of primaries • Choice of primaries=choice of color matching functions=choice of color space • Color matching functions, hence color descriptions, are all within linear transformations • RGB: primaries are monochromatic, energies are 645.2nm, 526.3nm, 444.4nm. Color matching functions have negative parts -> some colors can be matched only subtractively. • CIE XYZ: Color matching functions are positive everywhere, but primaries are imaginary. Usually draw x, y, where x=X/(X+Y+Z) y=Y/(X+Y+Z) CSE152, Spring 2011 Intro Computer Vision CIE xyY (Chromaticity Space) 2 CSE152, Spring 2011 Intro Computer Vision Binary System Summary 1. Acquire images and binarize (tresholding, color labels, etc.). 2. Possibly clean up image using morphological operators. 3. Determine regions (blobs) using connected component exploration 4. Compute position, area, and orientation of each blob using moments 5. Compute features that are rotation, scale, and translation invariant using Moments (e.g., Eigenvalues of normalized moments). CSE152, Spring 2011 Intro Computer Vision Histogram-based Segmentation • Select threshold • Create binary image: I(x,y) < T → O(x,y) = 0 I(x,y) ≥ T → O(x,y) = 1 [ From Octavia Camps] CSE152, Spring 2011...
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lec7 - 1 CSE152 Spring 2011 Intro Computer Vision...

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