Digital Image

02-01 Digital Image

  • What is a Digital Image?
  • How to make an image a computable entity?
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Digital Image Formats

Raster image formats store a series of colored dots “pixels.”

Number of bits for each pixel represents the depth of color.

  • 1 bit-per-pixel: 2 colors (black or white, binary).
  • 4 bits-per-pixel: 16 colors
  • 8 bits-per-pixel: 256 different colors

Images can also be 16, 24, 32 bits-per-pixel:

  • 24 bits per pixel usually means 8 bits per color
  • At the two highest levels, the pixels themselves can carry up to 16, 777, 216 colors

Common Raster Image formats

  • GIF, JPG, PPM, TIF, BMP etc.
  • Will discuss camera RAW format.

Exercises

  • mathworks.com
  • opencv.org, python.org
  • processing.org

02-02 Point Processes

Image Processing and Filtering

  • Point Process Computations on an Image
  • How to combine intensities from 2 images.
  • Point-process computations
  • Add / Subtract Images
  • alpha-blending and it’s applications
  • Image histograms
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02-04 Smoothing

Image Processing and Filtering: Smoothing

  • Smooth an image over a neighborhood of pixels
  • Median Filtering as a special non-linear filtering and smoothing approach.
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Median Filtering

Median Filtering: Non Linear Operation often used in image processing.

  • Reduces noise, but
  • Preserves edges (Sharp Lines!)

Main Idea: Use median of all pixels in kernel area, instead of mean.

02-05 Convolution and Cross-Correlation

02-06 Gradients

02-07 Edges