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A Scanning Primer

A Scanning Primer. Presented by: Beth Nicol & Todd Jennings. Overview. Resolution Color Space File Types OCR Compression De-Screening/Moiré Removal Image Touchup. Resolution (DPI/PPI). DPI > “Dots Per Inch” PPI > “Pixels Per Inch”

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A Scanning Primer

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  1. A Scanning Primer Presented by: Beth Nicol & Todd Jennings Digital Library Leadership Montgomery, AL ● April 20, 2004

  2. Overview • Resolution • Color Space • File Types • OCR • Compression • De-Screening/Moiré Removal • Image Touchup Digital Library Leadership Montgomery, AL ● April 20, 2004

  3. Resolution (DPI/PPI) • DPI > “Dots Per Inch” • PPI > “Pixels Per Inch” • Image resolution is measured in the number of pixels (equally sized squares) can be laid down over an image. • “a picture element” • the smallest element that can be assigned one and only one color or shade value Digital Library Leadership Montgomery, AL ● April 20, 2004

  4. Resolution Examples Digital Library Leadership Montgomery, AL ● April 20, 2004

  5. Bit Depth: Terms • “BiTonal” > 1-bit • A one-digit string > 1 or 0 > black or white • “Grey Scale” > not more than 8-bit • an eight-digit string > 256 colors or shades • “True Color” > not less than 24-bit • a twenty-four digit string > 16,777,216 colors Digital Library Leadership Montgomery, AL ● April 20, 2004

  6. Color Space • sRGB • “standardized” Red / Green / Blue • optimized for screen viewing • CMYK • Cyan / Magenta / Yellow / Black • Optimized for printing Most library and image digitization is archived in the sRGB color space, i.e. for delivery on screen Digital Library Leadership Montgomery, AL ● April 20, 2004

  7. File Types • Raster Format • graphic created by using a grid • Vector Format • scalable, graphic created by mathematical equation • Text Format • used with OCR capture, recognizes characters/scripts & some symbols Digital Library Leadership Montgomery, AL ● April 20, 2004

  8. File Types: Raster Format • GIF – “Graphic Image File” • 256 colors; used for most web graphic design • owned by Unisys • JPEG – “Joint Photographic Engineers Group” • can be saved using true-color or grayscale • considered to be the standard for image web display • TIF – “Tagged Image File” • can save images as grayscale, color palette, or true-color images • usually used for master copies of an image • PNG – “Portable Network Graphic” • can be saved using true-color, palette, or grayscale • will supposedly replace GIFs Digital Library Leadership Montgomery, AL ● April 20, 2004

  9. 5 kbGIF 14 kbJPG 23 kbTIF 42 kbPNG File Types: Raster Format (examples) Digital Library Leadership Montgomery, AL ● April 20, 2004

  10. 32 kb GIF 111 kb JPG 201 kb PNG 371 kb TIF File Types: Raster Format (examples) Digital Library Leadership Montgomery, AL ● April 20, 2004

  11. File Types: Vector Format • PDF – “Portable Document Format” • common format for distribution of documents (especially magazines, journals, books, etc.) • http://www.adobe.com/products/acrobat/main.html • LizardTech MrSID • common format for distribution of maps and other large image materials • http://www.lizardtech.com Digital Library Leadership Montgomery, AL ● April 20, 2004

  12. File Types: Text Format • ASCII • Most Western characters/scripts and some symbols • 8-bit coding • UNICODE • All known world characters/scripts and almost all symbols • 16-bit coding ASCII will be standard, use UNICODE only as necessary to represent characters not in ASCII subset Digital Library Leadership Montgomery, AL ● April 20, 2004

  13. File Types: Text Format • OCR – “Optical Character Recognition” • process used to translate graphic images into character based format • the OCR process analyzes a document for light and dark areas in order to identify each alphabetic letter or numeric digit • some fonts or damaged copies may cause conversion errors when rendering text Digital Library Leadership Montgomery, AL ● April 20, 2004

  14. Compression • Lossless • Lossy Digital Library Leadership Montgomery, AL ● April 20, 2004

  15. Compression: Lossless • Retains all of the original image data • Ideal for image archiving (“off-line storage”) • fullest possible image capture • Ideal for viewing detail • Literally every bit of information is present • Ideal for high-quality printing • Again, every bit of image information is present Lossless file formats: PNG, TIF, GIF Digital Library Leadership Montgomery, AL ● April 20, 2004

  16. Compression: Lossy • Reduces file size by eliminating data • Ideal for “on-line storage” • the smaller the files, the more files one can store • Ideal for web delivery • the smaller the file, the quicker it is delivered from point A to point B • Acceptable for web viewing • the human eye is tolerant, it fills in the gaps • there are limits: not every lossy image can be tolerated Lossy file formats: JPEG Digital Library Leadership Montgomery, AL ● April 20, 2004

  17. 22 kb100% Compression 44 kb75% Compression 79 kb50% Compression 154 kb25% Compression Acceptable Loss? B/W Examples 315 kb JPG 0% Compression Digital Library Leadership Montgomery, AL ● April 20, 2004

  18. 81 kb25% compression 39 kb50% compression 23 kb75% compression 11 kb100% compression Acceptable Loss? Color Examples 256 kbJPG0% compression Digital Library Leadership Montgomery, AL ● April 20, 2004

  19. De-Screening/Moiré Removal • Moiré Effect (also called the Water Effect) • a visual perception that occurs when a set of lines or dots that is superimposed on another set of lines or dots, where the sets differ in relative size, angle, or spacing • in other words... Digital Library Leadership Montgomery, AL ● April 20, 2004

  20. Original File File w/ Moiré Effect Removed De-Screening/Moiré Removal Digital Library Leadership Montgomery, AL ● April 20, 2004

  21. Image Touchup • Brightness/Contrast • Negatives • Layers • Color Settings • Slicing • Feather/Masking Digital Library Leadership Montgomery, AL ● April 20, 2004

  22. Original Image Adjusted Image Brightness/Contrast Digital Library Leadership Montgomery, AL ● April 20, 2004

  23. Original 35mm Negative Inverted 35mm Negative Negatives Digital Library Leadership Montgomery, AL ● April 20, 2004

  24. File w/ added layers Layers Original File Digital Library Leadership Montgomery, AL ● April 20, 2004

  25. Original File File w/ adjusted input level Color Settings Digital Library Leadership Montgomery, AL ● April 20, 2004

  26. Slicing Digital Library Leadership Montgomery, AL ● April 20, 2004

  27. Feather/Masking Digital Library Leadership Montgomery, AL ● April 20, 2004

  28. Any Questions? Todd Jennings Beth Nicol (334) 844-1794 (334) 844-1731 jennito@auburn.edunicollb@auburn.edu Digital Library Leadership Montgomery, AL ● April 20, 2004

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