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 Overview 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

Digital Library Leadership Montgomery, AL ● April 20, 2004 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

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

Digital Library Leadership Montgomery, AL ● April 20, 2004 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 “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 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 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 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 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 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 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 File Types: Raster Format (examples) 5 kb GIF 14 kb JPG 23 kb TIF 42 kb PNG

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

Digital Library Leadership Montgomery, AL ● April 20, 2004 File Types: Vector Format PDF – “Portable Document Format”PDF – “Portable Document Format” –common format for distribution of documents (especially magazines, journals, books, etc.) – LizardTech MrSIDLizardTech MrSID –common format for distribution of maps and other large image materials – PDF – “Portable Document Format”PDF – “Portable Document Format” –common format for distribution of documents (especially magazines, journals, books, etc.) – LizardTech MrSIDLizardTech MrSID –common format for distribution of maps and other large image materials –

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

Digital Library Leadership Montgomery, AL ● April 20, 2004 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 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 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 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 Acceptable Loss? B/W Examples 315 kb JPG 0% Compression 22 kb 100% Compression 44 kb 75% Compression 79 kb 50% Compression 154 kb 25% Compression

Digital Library Leadership Montgomery, AL ● April 20, 2004 Acceptable Loss? Color Examples 256 kb JPG 0% compression 81 kb 25% compression 23 kb 75% compression 39 kb 50% compression 11 kb 100% compression

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

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

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

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

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

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

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

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

Digital Library Leadership Montgomery, AL ● April 20, 2004 Any Questions? Todd JenningsBeth Nicol (334) (334) Todd JenningsBeth Nicol (334) (334)