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

Digital Library Leadership

Montgomery, AL ● April 20, 2004

A Scanning Primer

A Scanning Primer

Presented by: Beth Nicol & Todd Jennings



OverviewOverview• Resolution• Color Space• File Types• OCR• Compression• De-Screening/Moiré Removal• Image Touchup

• Resolution• Color Space• File Types• OCR• Compression• De-Screening/Moiré Removal• Image Touchup



Resolution (DPI/PPI)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

• 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



Resolution ExamplesResolution Examples



Bit Depth: TermsBit 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

• “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



Color SpaceColor 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

• 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



File TypesFile 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

• 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



File Types: Raster FormatFile 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

• 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



File Types: Raster Format (examples)File Types: Raster Format (examples)

5 kbGIF

14 kbJPG

23 kbTIF

42 kbPNG

http://www.auburntigers.com/fuseads/track/track.cfm?BannerID=101&PathInfo=/banners/promotions.cfm&catid=8



File Types: Raster Format (examples)File Types: Raster Format (examples)

32 kbGIF 111 kb

JPG 201 kbPNG 371 kb

TIF



File Types: Vector FormatFile Types: Vector Format• PDF – “Portable Document Format”PDF – “Portable Document Format”

– common format for distribution of documents common format for distribution of documents (especially magazines, journals, books, etc.)(especially magazines, journals, books, etc.)

– http://www.adobe.com/products/acrobat/main.html

• LizardTech MrSIDLizardTech MrSID– common format for distribution of maps and common format for distribution of maps and

other large image materialsother large image materials– http://www.lizardtech.com

http://www.adobe.com/products/acrobat/main.html

http://www.lizardtech.com/



File Types: Text FormatFile 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

• 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



File Types: Text FormatFile 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

• 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



CompressionCompression• Lossless• Lossy

• Lossless• Lossy



Compression: LosslessCompression: 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

• 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



Compression: LossyCompression: 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

• 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



Acceptable Loss? B/W ExamplesAcceptable Loss? B/W Examples

315 kbJPG

0% Compression

22 kb100%

Compression

44 kb75%

Compression

79 kb50%

Compression

154 kb25%

Compression



Acceptable Loss? Color ExamplesAcceptable Loss? Color Examples

256 kbJPG

0% compression

81 kb25% compression






De-Screening/Moiré RemovalDe-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...

• 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...



Original FileFile w/ Moiré Effect Removed

De-Screening/Moiré RemovalDe-Screening/Moiré Removal



Image TouchupImage Touchup• Brightness/Contrast• Negatives• Layers• Color Settings• Slicing• Feather/Masking

• Brightness/Contrast• Negatives• Layers• Color Settings• Slicing• Feather/Masking



Brightness/ContrastBrightness/Contrast

Original Image

Adjusted Image



NegativesNegatives

Original 35mm Negative

Inverted 35mm Negative



LayersLayers

Original File File w/ added layers



Color SettingsColor Settings

Original File

File w/ adjusted input level



SlicingSlicing



Feather/MaskingFeather/Masking



Any Questions?Any Questions?

Todd Jennings Beth Nicol(334) 844-1794 (334) [email protected] [email protected]

mailto:[email protected]

mailto:[email protected]

Documents

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