**** Digitization. Pictures are important

Transcription

1 **** 1 Digitization by Paul.Nieuwenhuysen@vub.ac.be Prepared to support a tutorial presentation in the framework of OceanTeacher Academy at UNESCO-IOC-IODE in Oostende, Belgium

2 **** 2 Digitization Pictures are important

3 **** 3 Why learn the basics of pictures? Pictures/graphics/images are often inserted in» word processing documents» presentations with slides» web pages Therefore, it is interesting to know how» to acquire pictures» to change or improve pictures» to adapt pictures to the chosen output medium

4 **** 4 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 structure that can be browsed This can be needed at a personal or institutional level, as a component of digital assets management.

5 **** 5 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.

6 **** 6 Digitization Raster graphics versus vector graphics

7 **-- 7?? Question?? Explain the differences between raster (= bitmap) graphics and vector graphics.

8 **-- 8!! Task!! Create a small circle with a paint program for bitmap/raster graphics and save this as a file. Create a small circle with a draw program for vector graphics and save this as a file. Open each of both files again applying the same program that you used to create it and ENLARGE the circle.

9 **-- 9!! Task!! What is the difference between the resulting drawings (on screen as well as printed)? Consider the difference in size between the file with raster graphics and the file with vector graphics.

10 **-- 10 Graphics formats: bitmaps and vector graphics Bitmap/raster graphics used in programs for painting Vector-based graphics used in programs for drawing

11 **-- 11 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

12 **-- 12?? Question?? In which procedures are vector-based graphics converted to bitmap/raster graphics?

13 **-- 13?? Question?? Why can bitmap/raster graphics not be as easily converted to vector graphics, as vector graphics can be converted to bitmap/raster graphics?

14 **-- 14?? Question?? What is easier: Converting bitmap/raster graphics to vector graphics or the other way? Explain.

15 ***-Examples 15 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...

16 **--Examples 16 Graphics formats for vector graphics (+ bitmaps) File name extension CDR CGM EPS SVG... Name / Origin Corel Draw! Graphics Metafile Encapsulated PostScript Scalable Vector Graphics...

17 **-- 17 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.

18 **-- 18!! Task!! Incorporate a picture, stored in a graphics file, in a document created by your program for word processing. Which procedures do you know to accomplish this?

19 **** 19 Digitization Bitmap pictures

20 **-- 20!! Read!! Read a brief introduction to digital imaging: Cornell University Library / Research department Moving theory into practice: digital imaging tutorial. [online] Available from: [cited 2004] 1. Basic terminology (key concepts) 2. Selection

21 **** 21 How to obtain computer files with images/pictures? from printed material (by scanning) from the collection of clip art delivered with the software to create presentations from the WWW or an intranet by making photographs yourself (by saving to disk)

22 **-- 22 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.

23 **--Examples 23 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.

24 **--Examples 24 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 simple saving in PowerPoint with Tools Compress pictures allows some compression

25 **--Examples 25 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

26 **--Examples 26 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.

27 ***-Examples 27 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

28 ***-Examples 28 Software suitable to edit image files, independent of Microsoft: examples Corel PhotoPaint suitable to create JPG files; commercial software Adobe PhotoShop Adobe PhotoShop Elements suitable to create JPG files; powerful, expensive, and complicated program suitable to create JPG files; powerful program, much cheaper than the full PhotoShop

29 ***- 29?? Question?? Which program will YOU use to improve your digital photos and other pictures?

30 ***- 30 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)

31 ***- 31?? Question?? 1. Which computer hardware system do YOU use to store and retrieve your computer files? 2. Do you consider switching to a better system?

32 ***- 32 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)

33 ***- 33 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)

34 ***- 34 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

35 ***- 35 Creating pictures on computer for printing 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.

36 ***- 36 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

37 ***- 37?? Question?? Indicate on the gamut scheme the range of colors that cannot be printed.

38 ***- 38?? Question?? Indicate on the gamut scheme the range of colors that can be seen on the video monitor, but cannot be printed.

39 ***- 39?? Question?? Why can some colors be seen on the monitor, while a typical printer can NOT print them.

40 ***- 40?? Question?? Why can some colors NOT be seen on the monitor, while a typical printer can print them.

41 ***- 41!! Assignment!! 1. Find or create a relevant picture / photograph for printing. 2. Crop it (and perhaps further edit it) to make it suitable for printing. 3. Make a print-out that covers about half the surface of an A4 page in the center of that page.

42 ***- 42!! Task - Assignment - Exercise!! Inspect a picture that you have printed: Is the quality suitable for your kind of work? Do the printed colours correspond well enough to what you see on the computer display?

43 43

44 ***- 44 Creating pictures on computer for a presentation or web 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.

45 ***- 45 Creating pictures on computer for a presentation or web 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)

46 ***- 46 Creating pictures on computer for a presentation or web 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.

47 ***- 47 Creating pictures on computer for a presentation or web Save as JPEG file at an appropriate level of quality (or as a GIF file, if the number of colours < 256)

48 ***- 48 Creating pictures on computer for a presentation or web 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 .

49 ***- 49 Creating pictures on computer for a presentation or web 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

50 ***- 50?? Question?? How and when comes compressing pictures into the action of saving a file that contains a picture, using your program to create a PDF file?

51 ***- 51?? Question?? What is an important difference between creating pictures on computer for printing for a presentation or for a web

52 ***- 52 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.

53 ***- 53?? Question?? For which applications is the GIF file format appropriate? For which applications is the JPEG/JPG file format appropriate?

54 **-- 54?? Question?? Which properties of graphics file formats for bitmap images are important?

55 ***- 55 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

56 **-- 56?? Question?? For which type of image is GIF appropriate?

57 **-- 57?? Question?? On the WWW, GIF and JPG are mainly used, but nevertheless TIF is also important. Why?

58 ***- 58?? Question?? Which programs do you know and which program do you use to save images as JPEG/JPG files?

59 **-- 59 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.

60 **-- 60?? Question?? How many bits are needed to store a black-or-white picture element on computer?

61 **-- 61 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

62 **-- 62?? Question?? What is the maximum number of colours that your computer can display simultaneously with the appropriate settings of the software? (If you do not know, then check it with the software for the display settings.)

63 **** 63 Digitization Scanners

64 ***- 64?? Question?? Which applications do you know of scanners?

65 ***- 65 Scanners: applications document imaging, for archives and for document transmission using computer networks DTP = desk-top publishing (scanning pictures or insertion in your documents) FAX OCR = optical character recognition bar code scanning scanning of signatures for on-line comparison with images stored in the central computer...

66 ***- 66?? Question?? Which types of scanners do you know?

67 ***- 67 Scanners: various types Flatbed scanners! Hand-held scanners Sheet feeding scanners Drum scanners Film scanners Photo CD system Digital cameras Barcode scanners

68 ***-!! Assignment!! Make a scan of a complicated document that includes your portrait, such as your passport or identity card or student card, at a resolution of 600 dpi or higher; save these data in a file format without compression and loss of quality; write down the file size.

69 ***- 69!! Assignment!! 2. Make a printout based on the scanned data, at double size in colours or black and white.

70 ***- 70!! Assignment!! 3. Save the file that you obtained by scanning; use the JPG file format at the highest quality offered by the computer program that you use; write down the name of the computer program that you use and the resulting file size.

71 ***- 71!! Assignment!! 4. Compare the size of the created files, one NOT compressed, the other with lossy compression the quality of the pictures in both files

72 **-- 72!! Assignment!! Estimate the typical size of a computer file that contains a bitmap image in black or white only (no grey values), that has been obtained by using a typical scanner at 300 dpi, scanning a printed page of A4-size, when no data compression is applied.

73 **-- 73!! Assignment!! Estimate the typical size of a computer file that contains a bitmap image in colours (with 256 levels for each of the primary colours), that has been obtained by using a typical scanner at 300 dpi, scanning a printed page of A4-size, when no data compression is applied.

74 **-- 74!! Assignment!! Estimate the typical size of a computer file that contains a bitmap image in colours (with 256 levels for each of the primary colours), that has been obtained by using a typical scanner at 600 dpi, scanning a printed page of A4-size, when no data compression is applied.

75 **-- 75!! Assignment!! Compare digitizing a common paper document using a typical, contemporary, common 1. flatbed scanner 2. digital camera More concretely, compare the resulting a. number of picture elements b. color depth/resolution

76 **-- 76 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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