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From Analog to Digital
What are Digital Images?
Electronic snapshots taken of a scene or scanned from documents
sapreted either as black or white
Effects of Threshold
threshold = 100
threshold = 60
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Bit Depth
Determined by the number of binary digits (bits) used to represent each pixel
1-bit
8-bit
24-bit
Bit Depth
increasing bit depth increases the level of gray or color information that can be represented and arithmetically increases file size
Bit depth, dynamic range, and color appearance
Utilizing Sufficient Bit-Depth
3-bit gray
8-bit gray
Utilizing Sufficient Bit Depth
8-bit color
24-bit color
Bit Depth vs. Dynamic Range
The range of tonal difference between lightest light and the darkest dark
Mapping Tones Correctly: Use of Histograms
Representing Color Appearance
Balanced Color
Color Shift Towards Red
Image Enhancement
Image editing to modify or improve an image
filters (brightness, contrast, sharpness, blur)
tone and color correction
Use raises concerns about fidelity and authenticity
Effects of Filters
no filters used
maximum enhancement
Image Editing
Compression
reduces file size for processing, storage, transmission, and display
image quality may be affected by the compression techniques used and the level of compression applied
Compression Variables
lossless versus lossy compression
proprietary vs. open schemes
level of industry support
bitonal vs. gray/color
see attributes of common compression techniques at: -
Effects of JPEG Compression
300 dpi, 8-bit grayscale
uncompressed TIFF
JPEG :1 compression
Compression /File Format Comparison
GIF (lossless)
File Size: 60 KB
JPEG (lossy)
File Size: 49 KB
images courtesy of Edison Papers
File Formats
Consist of both the bits that comprise image information and header information on how to read and interpret the file
Image q