Page 203 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 12: Image Format

notes
JIF JPEG Related Image format
MAC MacPaint
MSP MacPaint New Version
PCT Macintosh PICT format
PCX ZSoft Paintbrush
PPM Portable Pixel Map (UNIX)
PSP Paint Shop Pro format
RAW Unencoded image format
RLE Run-Length Encoding (Used to
lower image bit rates)
TIFF Aldus Corporation format
WPG WordPerfect image format

The GIF file format does not support some basic image properties such as print
resolution. You should use different file format like PNG.

12.1.3 pixels and the Web
There is a delicate balance between the crispness of a picture and the number of pixels needed to
display it. Let’s say you have two images, each is 5 inches across and 3 inches down. One uses 300
pixels to span those five inches, the other uses 1500. Obviously, the one with 1500 uses smaller
pixels. It is also the one that offers a crisper, detailed look. The more pixels, the more detailed the
image will be. Of course, the more pixels the more bytes the image will take up.
So, how much is enough? That depends on whom you are speaking to, and right now you are
speaking. It always go with 100 pixels per inch. That creates a ten-thousand pixel square inch. It
found that allows for a pretty crisp image without going overboard on the bytes. It also allows
some leeway to increase or decrease the size of the image and not mess it up too much.

The lowest go is 72 pixels per-inch, the agreed upon low end of the image scale. In terms of pixels
per square inch, it is a whale of a drop to 5184. Try that.
12.1.4 Meta/vector image formats

You may not have heard of this type of image formatting, not that you had heard of Raster,
either. This formatting falls into a lot of proprietary formats, formats made for specific programs.
CorelDRAW (CDR), Hewlett-Packard Graphics Language (HGL), and Windows Metafiles (EMF)
are a few examples.
Where the Meta/Vector formats have it over Raster is that they are more than a simple grid of
coloured dots. They are actual vectors of data stored in mathematical formats rather than bits
of coloured dots. This allows for a strange shaping of colours and images that can be perfectly
cropped on an arc. A squared-off map of dots cannot produce that arc as well. In addition, since
the information is encoded in vectors, Meta/Vector image formats can be blown up or down
(a property known as “scalability”) without looking jagged or crowded (a property known as
“pixelating”).
So that do not receive e-mail from those in the computer image know, there is a difference in Meta
and Vector formats. Vector formats can contain only vector data whereas Meta files, as is implied
by the name, can contain multiple formats. This means there can be a lovely Bitmap plopped right
in the middle of your Windows Meta file.
12.1.5 Compression

“Compression” is a computer term that represents a variety of mathematical formats used to
compress an image’s byte size. Let’s say you have an image where the upper right-hand corner

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