Multimedia Programming 2005

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Multimedia Programming2005

• Class 2
• Computer Images

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Course Notes
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Remember to hand in your assignment before 1700
  TODAY!
• Assignments will be graded in the next week
• Results will be send over email
• I saw a Visual C CDROM lying around this place.

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Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment
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Contents
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Introduction
• Human eye
• Computer representation
• Image types
• Computer challenges
• Image programming
• Assignment

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Introduction
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Computer images are everywhere
• Holiday pictures
• Internet pages
• Computer documents
• Icons, buttons, windows, etc.
• Different types
• GIF, PNG, BMP, JPEG, TIFF, etc..
• What are computer images?

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Human Eye
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment
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Human eye vs. CCD
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• CCD charge coupled device
• Eye 150.000 elts/mm2
• CCD 4 Megapixel ?
• 4.000.000 elts/5mm2
• 160.000 elts/mm2
• Well within the realm of eye ability
• Intelligence in vision

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About color
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Humans discern thousands of colors
• The color spectrum contains roughly 6 colors
  (violet, blue green, yellow, orange, red)
• Cones are divided in categories
• Red (65), Green (33), blue (2)

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About color
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• All the colors of light are described in
  combinations of RGB
• Primary colors of light
• Secondary colors of light
• Colors of colorants or pigments

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Computer representation
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Divide picture in grid
• Take average color per cell
• Cells are called pixels

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Computer representation
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• RGB color space
• Give every pixel a RGB code (or index number)
• This color in RGB 255,128, 64
• This color in binary
• 00000000 010000000 10000000 11111111
• This color in hexadecimal
• 0x00 40 80 FF

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Computer representation
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• type .
• .
• Width.
• pixel1,pixel2,pixel3,pixel4, etc

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Computer terminology
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Dimensions of image in pixels
• WRONG resolution
• RIGHT size
• Determine resolution on output-time
• Color depth
• Number of colors available per pixel
• Monochrome, grayscale, 256 colors, true colors

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Image types
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• BMP (Bitmap)
• Varies from 2 to 16 million colors
• Uncompressed
• 4 bytes per pixel. (so large file)
• GIF (Compuserve GIF)
• 256 colors (of choice)
• Compressed (LZW, patented)
• 1 byte per pixel (colors in header)

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Image Types
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• JPEG (Joint Photographic Experts Group)
• Transformed color space (brightness, color).
• Encoding () in high frequency region (human eye
  can see badly)
• Downsampling per 8x8 pixels.
• Vector images

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Challenges object recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment
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Challenges object recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Not that different
• Main color red
• Surrounding color mostly green

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Challenges Human recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment
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Challenges Human recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Not that different
• Face
• Long black hair on both sides

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Challenges texture recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment
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Challenges texture recognition
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Not that different
• Main color white(ish)
• Texture shaded parts

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Visual programming
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Message loop
• while (!quit)
• readmessage()
• execute task(message)
• (Re)Paint the window is also a message!

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Image programming
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Simple image programming (no directX yet)
• Buffering is important!
• Disk is slow, memory is fast.
• On initialization load all images in memory to
  prevent shocks
• Display when needed.

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Image programming
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• All images are being displayed as uncompressed
  pixels (bitmap).
• Basic program flow
• Get window handle
• Create device handle
• Connect device handle to window handle
• Load image in device

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Image programming
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Start painting
• Draw bitmap
• End painting
• Invalidate window
• No worries skeleton code will be provided!

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Image programming example
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• //buffering
• hDC GetDC( hWnd )
• hdcImage CreateCompatibleDC(hDC )
• Bmp (HBITMAP)LoadImage(
• NULL,
• "..\\Images\\image01.bmp",
• IMAGE_BITMAP, NULL, NULL, LR_LOADFROMFILE )
• SelectObject( hdcImage, bmp )
• //displaying
• hDC BeginPaint( hWnd, ps )
• BitBlt( hDC, 0, 0, IMAGE_WIDTH, IMAGE_HEIGHT,
• hdcImage, 0, 0, SRCCOPY )
• EndPaint( hWnd, ps )
• InvalidateRect( hWnd, NULL, FALSE )

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Image programming example 2
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• // one time
• TransparentBlt(hdc, xStart, yStart, ptSize.x,
  ptSize.y,hdcTemp, 0, 0, ptSize.x,
• ptSize.y, cTransparentColor)
• //draw transparent picture
• myDrawTransparentBitmap(hdcSave,bmp_transparent
  ,250, 0, 0x0000ff00)

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Assignment
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• Ex. Windows message loop and images.
• Click a button to change image
• Move and place partially transparent images
• Automatically cycle through images to create
  (simulate video).

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Last assignment
Contents Introduction Human eye and image
physics Computer representation Image
Types Computer Challenges Image
Programming Assignment

• No correction yet.
• No chocolate bar award either.
• Any questions?