PCX format is one of the most usable graphic formats. Originally it was designed
by Zsoft for PC Paintbrush MS-DOS. That is why, it is also known as PC Paintbrush
format. Zsoft entered into a treaty with Microsoft. The latter was entitled
to use PCX format with other products, including Microsoft Paintbrush for Windows
(Microsoft Paintbrush program is delivered with each copy of MS Windows). As
a result, the format became of great importance not only for computers, based
on Intel processors, but also for the whole computer industry.

PCX files are used for graphic data storage and exchange in desktop publishing
system.

Originally the format was used to hold graphics and images, which contained
not more than 16 colors. This limitation was conditioned by IBM EGA display
construction (Enhanced Graphics). When IBM started to release VGA adapter (Virtual
Graphics Array), PCX format was revised to hold graphics and images, which contained
up to 256 colors.

The last PCX versions make possible to hold 24 bits color displays. Due to
this fact, the format can be generally used for graphic data operating. Unfortunately,
its compression algorithm is not effective enough to hold images with large pixel
intensity (read more about compression algorithms here).

Image data are encoded with the help of one of the RLE algorithm variants (read
more about this compression algorithm here). Using RLE algorithms, it is difficult
to foresee the end, for compressing factor is highly depended on image data
and on the number of colors, used in the concrete. Generally, image data, which
contain not more than 16 colors, decrease by 40-70% as compared with the original
file size. While 64 or 256 color images, which were scanned or videoed, decrease
only by 10-30%. Sometimes you can increase PCX file size via using compression algorithm for complex images.

You can use WMF files to hold vector and halftone images in working memory
or in disks with post output display. Windows Metafile format is a specific
Windows format. So it is supported by a lot of "non – Windows" applications
for data exchange with Windows applications. Out of Microsoft Windows interface
prevalence, WMF format is considered to be a general format for graphic applications
and is supported by all platforms.

Png file format is a comparatively new progressive format originally designed
to replace dated Gif. Png format has got a set of new features that Gif lacks.

Png also performs a lossless compression with the help of Deflate algorithm
(read more about Deflate algorithm here) and supports interlaced mode. The format
handles 256 transparency levels (that means that images might be partially transparent).
The fact, that the format supports color depth up to 48 bits and performs a
lossless compression, makes possible to hold photorealistic images. They won’t
lose its quality while compressing and decompressing.

Png format is used specially for networking.

The format was released in 1986 and was generally used to hold scanned white
and black images (Tiff 3.0). Released in 1987, Tiff 4.0 got prevalence for it
supported incompact color RGB images. Tiff 5.0 format, released in 1988, made
possible to hold palette color images and support LZW compression algorithm (read
more about LZW compression algorithm here). , Released in 1992, Tiff 6.0, supported
CMYK and YcbCr color images and Jpeg compression algorithm (read more about Jpeg
compression algorithm here).

The current Tiff (Tiff 6.0) is a rich and flexible file format, supported by
many programs. The format is capable to record halftone images with different
pixel intensity. So, it is considered to be a perfect format for graphic data
storage and processing.

Tiff format is one of the most multipurpose and integrated raster formats.
It is easily ported among platforms and used for different purposes (besides
Internet).

Bitmap is a home Windows raster format, which is used practically for all possible
raster data storage.
All BMP versions were designed for computers with Intel processors. The current
format version is device independable (that means that Bitmap determines the
pixel’s color without reference to display device) and makes possible to record
images of a different quality level (to the point of 32 bits). After revising,
the format was used to hold color and black and white images, so it became
general. The main advantage of the format is considered to be its usability
and wide software support.

Compression algorithm, used in BMP format, is one of the RLE run-length encoding
variants (read more about RLE compression algorithm here). But most files are
hold incompact.

Gif file format is used to hold and transfer images in index color mode (not
more than 256). The format also supports a lossless LZW compression algorithm
(a single file may contain a set of images) and interlaced mode (interfaced
image load).

In 1989 the format was updated. The name of the new version looks like gif89.
It supports an additional channel to perform a transparency effect and to hold
a set of images in a single file where frame show time and animation were displayed.

Nowadays the format is one of the most popular graphic formats. Though it not
suited to hold a photorealistic images, for it cannot contain more than 256
colors. It is mostly used to display animation and drawing pictures without
blend.

Gif format file has got a set of compression algorithm features that allows compressing
images with sequential horizontal colors. That means that a file, which contains
horizontal bars, will take fewer places than the same file with vertical bars.

Gif format, unlike Jpeg format, use a lossless compression algorithm. That means
that while compression/decompression bits are not deleted. Gif uses a patent
compression /decompression algorithm, which is called LZW (Lempel Zev Welch).
Read more about the compression algorithm here.

Interlaced mode makes possible to refine images, as they are loaded. It is
very convenient for big files, as you can see the main image features in several
seconds after loading.

Jpeg format was designed to transfer graphic data and images via digital telecommunication
networking and was generally used to hold and transfer full color photorealistic
images. Before Jpeg, there were very few formats, which supported 24 bit halftone
images. TIFF and BMP formats allowed holding 24 bit data, but they failed to
perform a lossless compression of the data, which contained thousand colors
from the real world, on the high quality level.

Jpeg compresses photos though with quality loss. Compression algorithm is that
data are deleted for deallocation (it allows to raise the compression degree).
Data are hold as pixel block in a certain color with intensity information
save (the matter is that a human eye discerns disintensity better than discoloration).

Photos and multi-color images, transferred in this format, are ideal for networking.

It is not possible to refine Jpeg images, though it is possible to debase them
by decreasing the file size.

Jpeg format is primarily used to hold photorealistic graphic images with a
large number of colors.

Compressed data capacity depends on image contents. Compression degree may
come up to 25:1 without visible loss in quality.

Jpeg supports Progressive Jpeg standard, which conceptually looks like interlaced
in Gif format. That means that Jpeg Progressive format images are loaded by
parts, which are displayed, as they are loaded. Such format is good for large
files. Unfortunately, it is a new standard, so some programs may not support
it.