Lecture Notes

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• Painting
• Rubber stamping
• Interpolation in image resizing
• Nearest neighbor
• Bilinear
• Bicubic

• Bitmap file formats
• File compression
• Lossy vs Lossless compression
• Jpeg
• Gif
• Tiff

• Image re-sampling:
• By adjusting this feature, one can decide how the computer extrapolates new pixels (if the image size is increased) or how the computer removes pixels if the image is made smaller. This can be done through three different methods:
• Nearest neighbor-the new pixel to be added or subtracted gains its traits from an adjacent pixel currently in existence.
• Bilinear-the traits of pixels to be added or subtracted are determined on the basis of the average characteristics of the pixels on either side of where the new pixel is to be placed using a 2 x 2 matrix. This method samples four pixel values where the nearest neighbor method samples one
• Bicubic-the traits of pixels to be added or subtracted are determined on the basis of the average characteristics of the pixels on all four sides of the location of where the new pixel is to be placed using a 4 x 4 matrix. This method samples 16 pixel values where the nearest neighbor method samples one.
• File formats.
• Content versus format
• Example of a title: filename.doc
• Where filename is the name the user decides is appropriate
• The period is the delimiter
• Doc is the extension determined by the format in which the file is being saved, in this case a Microsoft Word document file.
• Full path name
• Example C:\directory\directory\filename.ext
• C: is the drive designator.
• The first "\" is the root directory.
• The remaining "\" are all delimiters
• .  is a delimiter
• ext is a filetype or file extension.
• Tiff, gif, and jpeg
• Tiff’s (.tif) and gif’s (.gif) are both lossless file formats (data is not lost).
• Jpeg’s (.jpg) is a lossy file format (data is lost).
• Compression
• Tiff-tagged information file format
• No compression - therefore this is the largest file format
• Used for images destined for printing or plotting.
• Gif  Stands for Graphics Interchange Format
• If one has an image represented by the following: 1110000001100111111
• Gif compresses the data into what we can think of as: 1’s x 3; 0’s x 6; 1’s x 2; 0’s x 2; 1’s x 6
• A lossless file format
• User has no control over the amount of compression. The amount of compression is determined by the amount of repetition in the image, when scanned horizontally.
• Used for text or line images destined for projection or display.
• Jpeg’s Stands for Joint Photographic Experts Group
• Uses sampling
• A lossy file format.
• The user controls the amount of compression.
• Results in pixels being removed from the image.
• Used for photographs with significant color or tonal range and where detail is not required to be maintained.