Transcript Internet Graphics for Classroom Use

How to find and process
Internet Graphics
for Classroom Use
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
A lot of things can go wrong…
bleak colours…
low contrast…
limited colours…
blue tinge…
blue tinge…
blue tinge…
A lot of things can go wrong…
… but a lot can be improved.
Overview of the workshop
• Find (an image)
• Optimize it
• Use it effectively
Real (‘reverse’) overview
• A bit of theory
• Processing
• Search engines and software
• Tips and tricks
Theory – key concepts
• Pixel
• Resolution
• Compression
• Color depth
• Vector vs raster graphics
• File formats
Theory – pixel – 1
Magnified image – pixels visible
Pixels are
building
blocks of an
image.
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
Theory – resolution – 1
• The level of detail an image holds
• Unit: pixels/dots per inch
1 pixel per inch
2 pixels per inch
5 pixels per inch
The more
pixels per inch
the clearer the
image
Source: wikipedia.org
Theory – resolution 2
Resolution and quality
18 ppi
72 ppi
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
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
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.
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 colours
90 kB
7 colours
15 kB
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 by
y=x formula
Vector vs raster graphics
raster
vector
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
File formats
• Uncompressed: bmp, tif
• Compressed (lossless): gif, png
• Compressed (lossy): jpg
• Vector: wmf, emf
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’
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’
Basic processing using Irfan View
• Rotation
• Cropping
• Resizing/resampling
• Controlling color depth
• Improving contrast and saturation
• Enhancing colors
• Batch processing
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
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)
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
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
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
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
Dark areas to be removed
1. Run Paint NET
2. Click „Magic wand” or „Lasso
select”
3. Cut the unwanted parts
Batch processing
1. Run Irfanview
2. Go to File/Batch conversion/rename
3. Set parameters and press „Start”
Removing background in Powerpoint
1. Paste the image into PP
2. Click the image
3. In the image toolbar select „Make
area transparent”
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
Thank you!
[email protected]