Preservation and Archiving of Digital Assets. Still images

Transcription

1 1 Preservation and Archiving of Digital Assets Module about Still images Created for a training workshop in the framework of UNESCO-IOC-IODE OceanTeacher Academy at UNESCO-IOC-IODE in Oostende / Ostend, Belgium March 2010 by Paul.Nieuwenhuysen@vub.ac.be

2 2 These slides should be available from the WWW site (note: BIBLIO and not biblio) and from UNESCO-IOC-IODE

3 Background of the author/presenter: 1979 Doctorate = PhD, in Physics 1983 Post-doctoral degree in Science 1985 Full-time Member of Faculty, Vrije Universiteit Brussel, Belgium 1986 Master in Documentation and Library Science Guest Professor (Information and Library Science), University of Antwerp, Belgium 3

4 Activities of the author/presenter: 1. Advising the director of the university central library and information service 2. Link between University Library and the faculties of science and engineering 3. Teaching in information science 4. Organising international training programs on information services 5. Research in information science 6. Projects related to scientific information services 4

5 2 sessions of 90 minutes: 5 - contents -summary -structure - overview of this contribution 1. Images are important 2. Vector graphics versus bitmap graphics 3. Bitmap graphics: Software Picture file formats Compression of files (and relation with memory requirements) Resolution of images (and relation with memory requirements)

6 6 Pictures on computers Pictures are important

7 7 Why learn the basics of pictures? Scanning a document yields a picture, not a text. (OCR can then exploit the picture to yield a text in some cases.) Pictures in a collection must be managed:»storing»making backups»ordering / sorting pictures in a browsable structure» This can be needed at a personal or institutional level.

8 8 Why learn the basics of pictures? Documents are more and more made available through the Internet. Therefore it is important to make the file sizes small, while preserving an appropriate image/picture quality.

9 9 Pictures on computers Raster graphics versus vector graphics

10 10?? Question?? Explain the differences between raster (= (= bitmap) graphics and vector graphics.

11 11!! Task - Assignment!! Create a small circle with a paint program for bitmap/raster graphics and save this as as a file. Create a small circle with a draw program for vector graphics and save this as as a file. Open each of of both files again applying the same program that you used to to create it it and ENLARGE the circle.

12 12!! Task - Assignment!! What is is the difference between the resulting drawings (on screen as as well as as printed)? Consider the difference in in size between the file with raster graphics and the file with vector graphics.

13 13 Graphics formats: bitmaps and vector graphics Bitmap/raster graphics used in programs for painting Vector-based graphics used in programs for drawing

14 14 Graphics formats: bitmaps compared with vector graphics Property Suited for painting and retouching Resolution adapted to output medium Size of files Bitmap/Raster + - large Vector graphics - + small

15 15?? Question?? In In which procedures are vector-based graphics converted to to bitmap/raster graphics?

16 16?? Question?? Why can bitmap/raster graphics not be be as as easily converted to to vector graphics, as as vector graphics can be be converted to to bitmap/raster graphics?

17 17?? Question?? What is is easier: Converting bitmap/raster graphics to to vector graphics or or the other way? Explain.

18 Examples 18 Graphics formats for bitmaps only File name extension.bmp.gif.jpg.pcx,.pcc.png (PNG8, PNG24).RLE.TIF... Origin Microsoft bitmap CompuServe / Unisys JPEG Z-Soft Paintbrush W3C Microsoft compressed bitmap Aldus PageMaker...

19 Examples 19 Graphics formats for vector graphics (+ bitmaps) File name extension CDR CGM EPS IMG PPT or PPS SVG WPG... Name / Origin Corel Draw! Graphics Metafile Encapsulated PostScript GEM Microsoft PowerPoint Scalable Vector Graphics WordPerfect Graphics...

20 20 Graphics formats: the problem of exchange The differences in all the graphics file formats cause the requirement of filter / conversion programs, when a graphics file must be inserted in a document which is managed by an application program which works primarily with another graphics file format.

21 21!! Task - Assignment!! Incorporate a picture, stored in in a graphics file, in in a document created by by your program for word processing. Which procedures do do you know to to accomplish this?

22 22 Pictures on computers Bitmap pictures

23 23 How to obtain computer files with images/pictures? from the collection of clip art delivered with the software to create presentations from printed material from the WWW or an intranet by making photographs yourself (by scanning) (by saving to disk)

24 24 How to create digital photographs for use on computers? To obtain digitized photos to insert in your presentation file, you can»use a classical, chemical camera and digitize the results, by scanning the printed photo, using a page scanner by using a specialized scanner to scan the photo film by using the Kodak PhotoCD service through a good photo shop»use directly a digital camera!

25 25 Software to work with image files: categories Several types of computer programs can be used to work with pictures on computer: 1. To view individual picture files full screen and as a slideshow 2. To view/manage/organize picture files on a computer 3. To edit/improve pictures Of course these categories of software are overlapping. Ideally 1 software package offers all features.

26 Examples 26 Software suitable to view image files: examples The program to view pictures that comes with your operating system. Available without extra costs. Irfanview Freeware. Offers also some editing functions.

27 Examples 27 Software suitable to edit image files, produced by Microsoft: examples (1) Microsoft Paint The drawing module that is available to all application programs in the suite Microsoft Office 97, 2000 The drawing module that is available to all application programs in the suite Microsoft Office XP=2002, 2003 simple NOT suitable to create appropriately compressed files saving in PowerPoint with Tools Compress pictures allows some compression

28 Examples 28 Software suitable to edit image files, produced by Microsoft: examples (2) Microsoft PhotoEditor (part of Microsoft Office 97) Microsoft PhotoDraw 2000 Microsoft Digital Image Pro, Microsoft Photo Standard, Digital Image Suite suitable to create JPG files, but an obsolete program suitable to create JPG files; easy to use program

29 Examples 29 Software suitable to edit image files, produced by Microsoft: examples (3) Microsoft Office 2003 Picture manager Comes with Microsoft Office Replaces Photo Editor that came with earlier versions of Office, although it offers fewer editing features.

30 Examples 30 Software suitable to edit image files, independent of Microsoft: examples Irfanview OpenOffice Picasa The GIMP Serif Photoplus, older versions Serif Photoplus, newer versions Ulead Photoimpact Paint Shop Pro, by JASC, before 2004 Paint Shop Pro, by Corel, since 2004 Freeware Commercial software

31 Examples 31 Software suitable to edit image files, independent of Microsoft: examples Corel PhotoPaint suitable to create JPG files; commercial software Adobe PhotoShop 4, 5, 6, 7, CS, CS2, CS3, CS4 Adobe PhotoShop Elements 1, 2, 3, 4, 5, 6, 7 suitable to create JPG files; powerful, expensive, and complicated program suitable to create JPG files; powerful program, much cheaper than the full PhotoShop

32 32?? Question?? Which program will YOU use to to improve your digital photos and other pictures?

33 33 Creating and improving pictures on computer (1) Workflow: Scanning or PhotoCD or digital photography Archive = make backup on an external hard disk (consider using a RAID disk system for security) or DVD-R or DVD+R or DVD-RW or DVD+RW (or on CD-R or CD-RW)

34 34?? Question?? Which computer hardware system do do YOU use to to store and retrieve your computer files? Do Do you consider switching to to a better system?

35 35 Creating and improving pictures on computer (2) Use a graphics program and» Save (lossless) as a (big) master file, for instance in TIFF format, using lossless compression such as LZW during the saving (or not)» Rotate (if required)» Crop (if required)

36 36 Creating and improving pictures on computer (3)» Convert from colours to grayscale (if required)» Increase the overall tonal range (which also increases contrast) AND decrease or increase overall brightness (if required) (can be accomplished in 1 action)» Increase or decrease the overall contrast (if still required even after increasing the tonal range)

37 37 Creating and improving pictures on computer (4)» Improve/change overall colors; for instance increase or decrease saturation (if required)» Dodge or burn = increase or decrease the brightness of particular areas manually» Apply one or several filters or effects (if required)» (Do NOT resize)» Check the resulting picture file in a full screen viewer and improve further if required

38 38 Creating pictures on computer for printing (1) Sharpen (if appropriate) (always as last step), using a sharpen/unsharp filter/effect: 1. Choose a suitable magnification on the display monitor to preview the sharpening. (In most cases so that the size of the picture on the display is close to the size that will be printed.) 2. Sharpen a maximum amount, only for the preview of the following steps.

39 39 Creating pictures on computer for printing (2) 3. In this preview mode, choose an appropriate range/radius for the sharpening. 4. Choose an appropriate value for the sharpening threshold, to avoid sharpening of unwanted noise. 5. Decrease the amount of sharpening to an appropriate level

40 40 Creating pictures on computer for printing (3) Save (lossless) (for instance in TIFF format) Archive = make backup of the improved, edited files, on an external hard disk or on DVD-R or DVD+R or DVD-RW or DVD+RW (or CD-R or CD-RW) Use a different disk than the one that holds your original master files; then in case that a disk is lost you still have the other file available. Load the improved file in your program for printing and print.

41 41 Colour ranges supported by video displays and printers Range of colours supported by various processes = gamut Visible colour gamut Saturated red Video display gamut Inkjet colour photo printer gamut Saturated green Saturated cyan Saturated yellow

42 42?? Question?? Indicate on on the gamut scheme the range of of colors that cannot be be printed.

43 43?? Question?? Indicate on on the gamut scheme the range of of colors that can be be seen on on the video monitor, but cannot be be printed.

44 44?? Question?? Why can some colors be be seen on on the monitor, while a typical printer can NOT print them.

45 45?? Question?? Why can some colors NOT be be seen on on the monitor, while a typical printer can print them.

46 46!! Assignment!! Learn Learn about about color color working spaces spaces from from Use Use your your computer to to read read this this document; do do not not print print it, it, because because the the colors colors and and links links are are important.

47 47!! Read!! Rodney, Andrew The Role of of Working Spaces in in Adobe Applications [online] Available free of of charge from: [cited 2009]

48 48!! Task - Assignment - Exercise!! Find or or create a relevant picture // photograph for printing Crop it it (and perhaps further edit it) it) to to make it it suitable for printing Make a print-out that covers about half the surface of of an an A4 A4 page in in the center of of that page.

49 49!! Task - Assignment - Exercise!! Inspect a picture that you have printed: Is Is the quality suitable for your kind of of work? Do the printed colours correspond well enough to to what you see on on the computer display?

50 50

51 51 Creating pictures on computer for a presentation or web (0) The following recommends a workflow from a digital picture file to a file for , web or presentation with digital projection. In some programs parts of this workflow are automated. For any intermediate save, save lossless, for instance in a TIFF format with lossless compression for instance with the name originalfilename-smaller.

52 52 Creating pictures on computer for a presentation or web (1) Open the starting picture file with your program. (In most cases you proceed with the file prepared as explained above.) If the file contains several layers and if you want to sharpen the picture, then flatten (= concentrate all information together) (because sharpening an image that contains layers may not work). Resize / resample (to make the file smaller)! Sharpen (if appropriate) (always as last step)

53 53 Creating pictures on computer for a presentation or web (2) In some advanced applications / workflows, the picture file may have a colour space profile such as the standard AdobeRGB profile, which is suitable for a colour space with a gamut that is bigger than the gamut of a computer display, then convert the profile to the standard srgb colour space profile as destination space profile that is more suitable for displays and projectors. In most workflows the starting picture file will already have the srgb profile attached or no profile at all.

54 54 Creating pictures on computer for a presentation or web (3) Save as JPEG file at an appropriate level of quality (or as a GIF file, if the number of colours < 256)

55 55 Creating pictures on computer for a presentation or web (4) Archive = make backup on an external hard disk or on DVD-R or DVD+R or DVD-RW or DVD+RW or on CD-R or CD-RW. Use a different disk than the one that holds your original master files; then in case that a disk is lost you still have the other file available. Insert in a slide or in a web page or use in .

56 56 Creating pictures on computer for a presentation or web (5) The considerations on compressing pictures are not only applicable to a pure, individual picture file, but also to a file that contains a document including 1 or several pictures. Examples: file saved by a program»for word processing»to create a presentation with slides»to produce a portable PDF file

57 57?? Question?? How and when comes compressing pictures into the action of of saving a file that contains a picture, using your program to to create a PDF file?

58 58?? Question?? What is is an an important difference between creating pictures on on computer for printing for a presentation or or for a web

59 59 Developing web documents: guidelines related to graphics File formats used mostly on a web are GIF, JPG, PNG, because the common browsers include viewers for the file formats. For each image/picture, use an appropriate graphics file format. Graphics/images/pictures take long to download. To speed things up, compress JPG (or PNG) files to make them as small as possible, while preserving an appropriate quality.

60 60?? Question?? For which applications is is the GIF file format appropriate? For which applications is is the JPEG/JPG file format appropriate?

61 61 Graphics file formats for bitmap pictures: a comparison BMP RLE GIF JPG PNG24 TIF (recent versions) Maximum number» of colours in one image of bits per pixel Compression of file size without loss of quality Maximum no. of pixels per image 256*256*256 = RLE x LZW + (but colours can be lost) x *256*256 = JPEG x more more 256*256*256 = more Multiple images in 1 file Animation is possible Can include layers

62 62!! Task - Assignment - Exercise!! Use Use a picture picture // photograph as as obtained with with a camera camera and and improved with with a suitable suitable program, to to include include it it in in a presentation or or a web. web Make Make it it smaller, so so that that the the resulting number of of picture picture elements is is suitable to to cover cover a typical typical projection screen screen as as far far as as possible Then Then save save it it as as a JPG JPG file file (not (not as as a component of of a presentation file file or or in in another another document file). file). (See (See the the example that that follows.)

63 63

64 64!! Task - Assignment - Exercise!! Select Select or or create create an an appropriate appropriate photograph photograph bitmap bitmap file. file. Save Save this this file file as as a a JPEG JPEGfile file under under a a different different name. name. Repeat Repeat this this at at about about 33 very very different different levels levels of of compression compression and and thus thus of of image image quality quality (always (always starting starting from from the the appropriate appropriate original original photo photo file, file, because because JPEG JPEG is is a a final final storage storage format). format). Load Load all all the the resulting resulting photo photo files files in in a a program program to to edit edit such such files; files; zoom zoom in in to to 400% 400% for for instance; instance; use use tiling tiling to to display display the the photo photo files files simultaneously simultaneously on on the the screen; screen; compare compare their their quality. quality. Determine Determine also also the the file file size size of of each each photo photo file. file. Decide Decide finally finally which which compression compression level level is is appropriate appropriate or or your your aims. aims.

65 65?? Question?? For which type of of image is is GIF appropriate?

66 66?? Question?? On the WWW, GIF and JPG are mainly used, but nevertheless TIF is is also important. Why?

67 67?? Question?? Which programs do do you know and which program do do you use to to save images as as JPEG/JPG files?

68 68?? Question?? Assume that you have a normal digital colour photo and that you want to to save it it with a particular number of of pixels in in a file that is is as as small as as possible. Which file format allows the smallest file size: GIF or or JPG?

69 69?? Question?? Why can we we say that JPG is is a file format for presentation only?

70 70?? Question?? When a photo is is made and saved as as a JPG file in in a digital camera, then information/quality is is lost. Camera producers know this. Why is is JPG used anyway?

71 71 Maximum number of colours displayed by computers: introduction The number of colours (including shades of a colour also) that can be displayed simultaneously on a computer screen/display is limited. This limitation is primarily caused by the limitations of the video/graphics card used by your computer.

72 72?? Question?? How many bits are needed to to store a black-or-white picture element on on computer?

73 73 Maximum number of colours displayed by computers: examples Examples of maximum number of colours on a computer display:»8-bit 2**8 = 256 : typical for older systems»16-bit 2**16 = = thousands of colors = High Color»24-bit 2**24 = (2**8)*(2**8)*(2**8) = 256*256*256 = True Color»32-bit 2**32: overkill for most applications

74 74?? Question?? What is is the maximum number of of colours that your computer can display simultaneously with the appropriate settings of of the software? (If (If you do do not know, then check it it with the software for the display settings.)

75 75 Maximum number of colours displayed by computers: consequences The computer system that is asked to display a graphics file with more colours than can be displayed simultaneously by the system will»dither the image to display it with less colours»shift colours to nearby colours that the system can display The result will depend on»the type of computer, and on»the particular application software that is used to display the file.

76 76 Developing documents for computers: guidelines related to colours Take into account / realize the limitations of computers and the variations in client computer hardware and software used to view your documents:»do not expect that all users will view the documents that you create and publish in the same way.»see that your colours are not essential for your message.

77 77!! Task - Assignment!! Estimate the typical size of of a computer file that contains a bitmap image in in black or or white only (no grey values), that has been obtained by by using a typical scanner at at 300 dpi, scanning a printed page of of A4-size, when no no data compression is is applied.

78 78!! Task - Assignment!! Estimate the typical size of of a computer file that contains a bitmap image in in colours (with 256 levels for each of of the primary colours), that has been obtained by by using a typical scanner at at 300 dpi, scanning a printed page of of A4-size, when no no data compression is is applied.

79 79!! Task - Assignment!! Estimate the typical size of of a computer file that contains a bitmap image in in colours (with 256 levels for each of of the primary colours), that has been obtained by by using a typical scanner at at 600 dpi, scanning a printed page of of A4-size, when no no data compression is is applied.

80 80?? Question?? Compare digitizing a common paper document using a typical, contemporary, common flatbed scanner digital camera More concretely, compare the resulting a. a. number of of picture elements b. b. color depth/resolution

81 81!! Read!! Read Johnson, Bob Color management: color models, color spaces and color profiles. [online] Available from:

82 82!! Read!! Read Relph-Knight, Terry Colour management: Colour perfect. Personal Computer World UK, August 2006, pp

83 83!! Read!! Read Color management.

84 84?? Question?? The common, popular file formats for pictures use bits or or less to to store each element=pixel. Explain that this forms a limitation for several practical applications from the user s point of of view.

85 85 Resizing of pictures: clearing up confusion The word resizing can create confusion, as it can be used and can be interpreted with various meanings:»changing the number of pixels in the picture file, which also affects the size of the picture file.»printing at a size that is different from the size in the object in reality OR from what is seen on a display.»applying a compression algorithm to the picture file to obtain a smaller file size.

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