Chapter 6 color shading
This presentation is the property of its rightful owner.
Sponsored Links
1 / 26

Chapter 6. Color & Shading PowerPoint PPT Presentation


  • 76 Views
  • Uploaded on
  • Presentation posted in: General

Chapter 6. Color & Shading. Perception of objects. Perception of objects. The spectrum (energy) of light source . The spectral reflectance of the object surface . The spectral sensitivity of the sensor. How do we see an object?. Light. Eyes. Object. Luminance  Lightness

Download Presentation

Chapter 6. Color & Shading

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Chapter 6 color shading

Chapter 6. Color & Shading


Perception of objects

Perception of objects


Perception of objects1

Perception of objects

  • The spectrum (energy) of light source.

  • The spectral reflectance of the object surface.

  • The spectral sensitivity of the sensor.


How do we see an object

How do we see an object?

Light

Eyes

Object

  • Luminance Lightness

  • Chrominance Color

Human eye is more sensitive to luminance than to chrominance


Light spectrum

Light Spectrum


Chromaticity diagram

Chromaticity Diagram


Rgb model

RGB Model


Rgb signals from a video camera

RGB signals from a video camera


Rgb colors

RGB Colors

  • Colors specify:

    • A mixture of red, green, and blue light

    • Values between 0.0 (none) and 1.0 (lots)

  • Color

  • Red Green Blue

  • White 1.0 1.0 1.0

  • Black 0.0 0.0 0.0

  • Yellow 1.0 1.0 0.0

  • Magenta 1.0 0.0 1.0

  • Cyan 1.0 1.0 0.0


Normalized rgb

Normalized RGB

r+g+b=1


Hsi model

HSI Model


Light vs pigment

Light vs. Pigment


Cmy model

CMY Model


Yiq model

YIQ Model

  • TV transmission  digital space YCBCR

  •  analog space YIQ (NTSC)

  •  YUV (PAL)


Yuv ycbcr model

YUV & YCBCR Model


Tv broadcast

TV Broadcast


Color histogram

Color Histogram

  • Color Histogram are relatively invariant to

    • Translation

    • Rotation

    • Scaling

  • Simple methods for color histogram construction

    • Concatenate the higher order two bits of each RGB color code.  64 bins

    • Compute three separate RGB histograms (4 bits each) and just concatenate them into one.  48 bins


Similarity measure for histogram matching

Similarity measure for histogram matching

  • It is common to smoothing the histogram before matching

  •  to adapt minor shifts of the reflectance spectrum.


Color segmentation

Color Segmentation

A plot of pixels (r,g) taken from different images containing faces.

(r,g) : normalized red and green values


Face detection

Face Detection

  • Face region classification. (R>G>B)

  • Connected Component Labeling.

  • Select the largest component as face object assuming there is only one face in the image.

  • Discard remaining components or merges them with the face object.

  • Computing the location of eyes and nose.


Shading

Shading


Three types of material reflection

Three types of Material Reflection

  • Diffuse Color of reflected light from diffuse reflection (light scattered randomly)

  • Ambient Amount of background light the surface reflects

  • Specular Color of reflected light from specular reflection (light reflected in a regular manner)


Diffuse reflection

Diffuse Reflection


Specular reflection

Specular Reflection


Darkening with distance

Darkening with Distance


Complications

Complications

  • The above models of illumination and reflection are simplified.

  • Some objects reflect light as well as emit light. For example: light bulbs.

  • In uncontrolled scenes, such as outdoor scenes, it is much more difficult to account for the different phenomena.


  • Login