how to find and process internet graphics for classroom use
TRANSCRIPT
![Page 1: How to find and process Internet Graphics for Classroom Use](https://reader035.vdocuments.site/reader035/viewer/2022062318/5516a5b7550346a25b8b5626/html5/thumbnails/1.jpg)
How to find and processInternet Graphicsfor Classroom Use
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Visual World
• One picture is worth a thousand words.
• A good picture is a worth a thousand pictures but ...
• ... a good picture requires processing to be fit for a given purpose
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A lot of things can go wrong…
bleak colours… low contrast… limited colours…
blue tinge… blue tinge… blue tinge…
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A lot of things can go wrong… … but a lot can be improved.
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Overview of the workshop
• Find (an image)
• Optimize it
• Use it effectively
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Real (‘reverse’) overview
• A bit of theory
• Processing
• Search engines and software
• Tips and tricks
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Theory – key concepts
• Pixel
• Resolution
• Compression
• Color depth
• Vector vs raster graphics
• File formats
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Theory – pixel – 1
Pixels are building blocks of an image.
Magnified image – pixels visible
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Theory – pixel – 2
• Information about each pixel in an image contains its detailed:−position in the picture (where to put
the given pixel)−precise colour description (how to
‘build’ colour of the pixel)
• An average ‘postcard’ size photograph contains more than 2 million pixels (1600x1200);
• The more pixels a given area has the better quality of the image is
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Theory – resolution – 1
• The level of detail an image holds
• Unit: pixels/dots per inch
Source: wikipedia.org
1 pixel per inch
2 pixels per inch
5 pixels per inch
The more pixels per inch the clearer the image
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Theory – resolution 2
72 ppi
18 ppi
Resolution and quality
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Theory – resolution – 3
• Optimum resolution for computer screen is 96 ppi (presentation, web)
• Optimum resolution for computer printout is 150 ppi (home printer)
• Optimum resolution for professional printing is 300 ppi and up
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Theory – compression
• Uncompressed high quality images take a lot of disk space (a single photograph about 10-25 MB)
• The process of compression reduces the amount of data by eliminating lengthy ‘descriptions’ of the pixels; one ‘description’ is used for all identical pixels or ...
• ... eliminating the differences between pixels the eye wouldn’t be able to see
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Theory – compression – types
• Lossless: data compression algorithms that allow the exact original data to be reconstructed from the compressed data.
• Lossy: data compression, which does not allow the exact original data to be reconstructed from the compressed data.
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Theory – colour depth
• Scientific experiments have shown that the number of colours we can see range as high as 10 million.
• Computers initially used 2, later 16, 256, 65 000 and now use 16,7 mln colours.
• The number of colours influences file size
16196 colours90 kB
7 colours15 kB
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Vector vs raster graphics
• Raster image – each point (pixel) of the image is described individually
• Vector image – the sequences of points are defined by mathematical formulas
The red line is described byy=x formula
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Vector vs raster graphics
vector
raster
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Why is all that so important?
• Number of pixels, resolution, compression, colour depth, type of graphics (raster/vector) determine the size and the quality of an image and its suitability for a given purpose
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File formats
• Uncompressed: bmp, tif
• Compressed (lossless): gif, png
• Compressed (lossy): jpg
• Vector: wmf, emf
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File formats - characteristics
• Bmp – too big for comfortable use; retains, however, all the important information
• Gif – only up to 256 colors can be represented (good for simple geometrical shapes, text)
• Jpg – full color (excellent for photographs)
• Wmf – small but ‘artificial looking’
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File formats - characteristics
• Bmp – too big for comfortable use; retains, however, all the important information
• Gif – only up to 256 colors can be represented (good for simple geometrical shapes, text)
• Jpg – full color (excellent for photographs)
• Wmf – small but ‘artificial looking’
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Basic processing using Irfan View
• Rotation
• Cropping
• Resizing/resampling
• Controlling color depth
• Improving contrast and saturation
• Enhancing colors
• Batch processing
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Where to look for good graphics
• Search engines http://www.google.com http://yotophoto.com
• Free stock photographs: http://www.sxc.hu/http://www.freefoto.com/ http://www.morguefile.com/http://www.freephotosweb.com/
• http://office.microsoft.com/clipart
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Software – free & commercial
• Irfanview (free) (www.irfanview.com)
• Paint NET (free) (http://www.getpaint.net)
• Photofiltre (free) (http://www.photofiltre.com)
• GIMP (free) (www.gimp.org)
• Adobe Photoshop (Adobe Elements) (www.adobe.com)
• Corel Photopaint (www.corel.com)
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Powerpoint presentation – too big
1. Process graphics (size, resolution, colors)
2. Save as gif/jpg files
3. Insert into the presentation
4. Link graphics instead of embedding it into the presentation (older Office software
• Steps 1-3 – use capture
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Dog image
1. Go to www.google.com and type dog; set search parameters
2. Good quality photograph: go to www.sxc.hu
3. Vector image: go to http://office.microsoft.com/clipart
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Only a part of an image is needed
1. Run Irfanview
2. Select the area you want to keep
3. Press Ctrl-Y
4. Save or copy image to buffer
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Too red, too pale, too dark
1. Run Irfanview
2. Press Shift+G (or go to Image/Enhance colors)
3. Change color balance
4. Save file
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Dark areas to be removed
1. Run Paint NET
2. Click „Magic wand” or „Lasso select”
3. Cut the unwanted parts
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Batch processing
1. Run Irfanview
2. Go to File/Batch conversion/rename
3. Set parameters and press „Start”
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Removing background in Powerpoint
1. Paste the image into PP
2. Click the image
3. In the image toolbar select „Make area transparent”
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Web browser – saving protected images and flash images
1. Find the image
2. Press „Print screen” key
3. Run Irfanview
4. Paste the captured screen
5. Edit (crop?) and save
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