1 / 53

Pictures on computers for scientists

Pictures on computers for scientists. Paul.Nieuwenhuysen@vub.ac.be Vrije Universiteit Brussel Information and Library Science, University of Antwerp Belgium Presented at VUB Brussels for doctoral researchers in May 2004. The slides are available from

etan
Télécharger la présentation

Pictures on computers for scientists

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Pictures on computers for scientists Paul.Nieuwenhuysen@vub.ac.be • Vrije Universiteit Brussel • Information and Library Science, University of Antwerp Belgium Presented at VUB Brussels for doctoral researchers in May 2004

  2. The slides are available from http://www.vub.ac.be/BIBLIO/nieuwenhuysen/presentations/ (note: BIBLIO and not biblio)

  3. contents - summary - structure • overview • of this tutorial • Pictures on computers • File formats for pictures • Bitmap pictures

  4. Is there a subject about which YOU personally would like to learn more?

  5. -Interruptions -Questions -Remarks -Discussions are welcome

  6. **** Pictures on computers File formats for pictures

  7. **-- ?? Question ?? Explain the differences between bitmap graphics with vector graphics.

  8. **-- Graphics formats: bitmaps and vector graphics • Bitmap graphics used in programs for “painting” • Vector-based graphics used in programs for “drawing”

  9. **-- Graphics formats: bitmaps compared with vector graphics • Property • Suited for “painting” and “retouching” • Resolution adapted to output medium • Size of files Bitmaps + - large Vector graphics - + small

  10. **-- !! Task - Assignment !! • Draw a small circle with a paint program for bitmaps and save this. • Draw a small circle with a draw program for vector graphics and save this. • Select each drawing and enlarge it. • What is the difference between the resulting drawings?

  11. **-- ?? Question ?? How can vector-based graphics be converted to a bitmap?

  12. **-- ?? Question ?? Why can bitmap graphics not be as easily converted to vector graphics, as vector graphics can be converted to bitmap graphics?

  13. ***-Examples 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 PaintbrushW3C Microsoft compressed bitmap Aldus PageMaker ...

  14. **--Examples Graphics formats for vector graphics (+ bitmaps) File name extension CDR CGM EPSIMG PPT or PPS WPG ... Origin Corel Draw! Graphics Metafile Encapsulated PostScript GEM Microsoft PowerPoint WordPerfect Graphics ...

  15. **-- 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.

  16. **-- !! Task - Assignment !! Incorporate a picture, stored in a graphics file, in a document created by your program for word processing.

  17. **** Pictures on computers Bitmap pictures

  18. **** Why learn the basics of bitmap pictures? • Bitmap pictures / graphics / images are often inserted in • word processing documents • presentations with slides • web pages • So it is interesting to know how to acquire and improve bitmap 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.

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

  20. ***- 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 by 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

  21. **-- !! Task - Assignment !! You can learn the basics of digital photography by reading for instance: Curtin, Dennis P. [online] Available from: http://www.shortcourses.com/choosing/[cited 2003]

  22. **-- !! Task - Assignment !! You can learn about developments in digital cameras by reading for instance: Freed, LesLook into the camera. (Camera technology)PC Magazine, January 20, 2004, pp. 107-114.

  23. 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 Microsoft PhotoEditor (part of Microsoft Office 97) Microsoft PhotoDraw2000… NOT suitable to create appropriately compressed files saving in PowerPoint XP with Tools | Compress pictures allows some compression suitable to create JPG files, but an obsolete program suitable to create JPG files; easy to use program **--Examples Software suitable to edit image files, produced by Microsoft: examples

  24. Irfanview JASC PaintShop suitable to create JPG files;freeware suitable to create JPG files; shareware ***-Examples Software suitable to edit image files, independent of Microsoft: examples

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

  26. ***- ?? Question ?? Which program will YOU use to improve your digitized photos?

  27. ***- Creating pictures on computer for printing (1) • Scanning orPhotoCDor digital photography • Save (lossless) as a (big) master file, for instance in TIFF format, using lossless compression such as LZW during the saving or not 

  28. ***- Creating pictures on computer for printing (2) • Use a graphics program and if required: 1. rotate2. crop3. convert to grayscale4. increase the tonal range (which also increases contrast)5. decrease or increase brightness 6. increase or decrease contrast7. increase (or decrease) color saturation 

  29. ***- Creating pictures on computer for printing (3) • (Do NOT decrease size, to keep high quality) • Sharpen (if appropriate) (always as last step) • Save (lossless) (for instance in TIFF format) • Print

  30. ***- Creating pictures on computer for a presentation or web (1) • Scanning or PhotoCD or digital photography • Save (lossless) as a big master file (for instance in TIFF format) 

  31. ***- Creating pictures on computer for a presentation or web (2) • Use a graphics program and if required: 1. rotate,2. crop, 3. convert to grayscale,4. increase the tonal range (which also increases contrast)5. decrease or increase brightness 6. decrease or increase contrast7. decrease or increase color saturation 8. resize/resample (to make the file smaller) 

  32. ***- Creating pictures on computer for a presentation or web (3) 9. Sharpen (if appropriate) (always as last step)10. Save (lossless) (for instance in TIFF format) 11. Save as JPEG file at an appropriate level of quality or as a GIF file • Finally: Insert in a slide or in a web page

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

  34. ***- !! Task - Assignment - Exercise !! Use a raw picture (a photograph) to include it in a presentation or a web. Improve this, make it smaller so that the resulting picture covers a complete typical projection screen, and save it as a JPG file. (See the example that follows.)

  35. *---

  36. **-- ?? Question ?? Why does the function in photo editing software, that is named “sharpen” not really sharpen your photo, in the sense that it does NOT increase the resolution of your photo. Then how does this work?

  37. **-- ?? Question ?? If you apply sharpening, then this should be the FINAL step in improving your picture. Why?

  38. ***- 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.

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

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

  41. 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 Multiple images in 1 fileAnimation is possible GIF 256 8 LZW + (but colours can be lost) 65535 x 65535 + + ***- Graphics file formats for bitmap pictures: a comparison BMP RLE 256*256*256 = 16 777 216 24 RLE + 65535 x 65535 - - JPG 256*256*256 = 16 777 216 24 JPEG - 65535 x 65535 - - PNG24 more 24 + - more - - TIF 256*256*256 = 16 777 216 24 + + more + +

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

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

  44. **-- !! Task - Assignment - Exercise !! Select or create an appropriate photograph bitmap file. Save this file as a JPEG file under a different name. Repeat this at about 3 very different levels of compression and thus of image quality(always starting from the appropriate original photo file, because JPEG is a final storage format). Load all the resulting photo files in a program to edit such files; zoom in to 400% for instance;use tiling to display the photo files simultaneously on the screen; compare their quality. Determine also the file size of each photo file. Decide finally which compression level is appropriate or your aims.

  45. **-- ?? Question ?? How long will a download of your photo file take approximately, in the case that not the Internet but the modem used by the receiving client is the bottleneck, the limiting factor in the data transfer?

  46. **-- ?? Question ?? Why can we say that JPG is a file format for presentation only?

  47. 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. **-- Maximum number of colours displayed by computers: introduction

  48. **-- Maximum number of colours displayed by computers: examples • Examples of limitations / maximum numberof colours on a computer display: • 8-bit = 2**8 = 256 typical for older systems • 16-bit = 2**16 = 65536 = “thousands of colors” = “High Color” • 24-bit = 2**24 = (2**8)*(2**8)*(2**8) = 256*256*256 =“True Color” • 32-bit = 2**32

  49. **-- ?? 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.)

  50. **-- 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.

More Related