ScannersCapture Devices - Home Department of Computer scannerscapture设备计算机家系.ppt

ScannersCapture Devices - Home Department of Computer scannerscapture设备计算机家系
What are Digital Images?
Electronic snBit 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 quality affected by format support for:
Bit depth
Compression techniques
Color management
Hardware,software, and network support
See common file formats chart at:
-
Equipment used and its performance over time
scanners with same stated functionality can produce different results
Factors affecting image quality:
Optical, mechanical, and sensing components
Calibration
Age of equipment
Environment
300 dpi, scanner A
300 dpi, scanner B
Variations in Imag