Image Processing with Matlab, Part 2

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• Misc
  • First hour exam
    • Friday, Oct. 10
    • Material since beginning of semester (e.g., basic expressions, vectors, matrices, plotting, scripts)
    • 3 - 5 short-answer questions
    • Whole class period
    • Open book, notes, computer; closed person
• Questions?
• Chroma Key Effects in Matlab
  • Examples
    • Backgrounds
      • “Easy” pictures, e.g., 1 - 2 colors
      • e.g., black-and-white (but this is really many shades of gray)
      • Make small images by hand
    • Subjects
      • Self in front of screen as subject
      • Hand-made images
      • Single-color objects
  • Algorithm ideas
    • Version 1
      

      chromakey( S, B )
          Subtract background color from S
          …

  • Creating and working with a 2-by-2 image by hand
    

    >> S = zeros( 2, 2, 3 )
    S(:,:,1) =
         0     0
         0     0
    S(:,:,2) =
         0     0
         0     0
    S(:,:,3) =
         0     0
         0     0
    >> S(:,:,1) = [128 128; 128 128]
    S(:,:,1) =
       128   128
       128   128
    S(:,:,2) =
         0     0
         0     0
    S(:,:,3) =
         0     0
         0     0
    >> S(:,:,2) = [255 255; 255 255]
    S(:,:,1) =
       128   128
       128   128
    S(:,:,2) =
       255   255
       255   255
    S(:,:,3) =
         0     0
         0     0
    >> S(:,:,3) = [255 255;255 255]
    S(:,:,1) =
       128   128
       128   128
    S(:,:,2) =
       255   255
       255   255
    S(:,:,3) =
       255   255
       255   255
    >> S( 1, 2, : ) = [0 0 0]
    S(:,:,1) =
       128     0
       128   128
    S(:,:,2) =
       255     0
       255   255
    S(:,:,3) =
       255     0
       255   255
    >> S2 = uint8( S );
    >> image( S2 )

• Next
  • Nail down algorithm

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