Lecture1/2: Canvas class

• Canvas: 2 Dimensional Pixel Array
  

• Safe version of pixel()

      RGB& pixel(int row, int col)               { return *(rgbs + row * hReso + col); }
  

  pixel() does not check the given row and column arguments. Using throw statement, try write another public member function, which checks both underflow and overflow.

      RGB& Pixel(int row, int col);
  

• Generate some images
  • A checkerboard

    void checkerboard(Canvas& canvas)
    {
      for(int row = 0; row < canvas.vReso; row++)
        for(int col = 0; col < canvas.hReso; col++)
        {
          canvas.Pixel(row, col) = (col/32 + row/32) % 2 ? White : Black;
        }
    }
    

  • Image Processing

    Try to download any image file, convert it to ppm format using IrfanView. Then read in the ppm image, and try to do any change you want to the image. After done, write back as another ppm file. Now again use IrfanView to enjoy your own work.

    Here are some ideas you may want to try.

    • flip the color
    • convert to gray level image
    • blur the image
    You should also take a look at photoshop or the like, to get some inspiration for what kind of image filtering you can possibly do with your Canvas class.

  • Any other patterns or shapes

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