Zinnia Bell

HOW DIFFERENT TYPES OF GRAPHIC IMAGES RELATE TO FILE FORMATS, FILE

CONVERSIONS, FORMATS AND COMPRESSION.

RAWimages are image files that have not yet processed, they contain minimally processed data from the image sensor of either a image scanner, motion picture film

scanner or digital camera. They are directly used in digital photography because they are the highest quality image

and contain a full resolution of 12 or 14 bit.

These files are usually used for large scale pieces such as for advertisements,

the only issues with this is the file is of high quality which means the size of the file is much bigger than that of other

image files such as JPEG.

Also RAW images are not suitable for websites because the image size increases the loading time considerable.

RAW

JPEG

JPEG is named after its creator the Joint Photographic Expert Group. They are the most common file format for images and are usually compressed from a RAW file in

order to reduce the size to something that’s more practical for daily use. The reason they are compressed to a smaller

size is so they may be used more usefully on things like websites, this is because the smaller sized images mean the

loading time is considerably less.

JPEG images give the best possible quality for the smallest file size and this is why they are so widely used and are also quick to download and are easily viewable on other devises

such as tablets and mobile phones.

GIF or Graphics Interchange Format is a low resolution bitmap image format used for simple logos, websites and symbols or icons. GIFS are mainly used in the animation

process as it gives the user the opportunity to make a moving images and also supports a transparent

background. Although, similar to a PNG file, it is of higher quality and has a slightly more limited colour spectrum, it

allows a separate palette on animations of up to 256 colours for each frame. This makes them unsuitable for

reproducing photographs but perfect for the use in making logos with solid areas of colours. GIF images are usually seen in web banner advertisements with sliding images.

GIF

PNG also known as Portable Network Graphics, PNG files are low resolution images and so are low quality images but

load a lot faster. PNG files were originally designed to replace GIF files and more specifically for transferring

images on the internet. They are not suitable however for professional quality print graphics as they do not support non-RGB colour spaces, and so are usually used for icons.

Like GIF, PNG files are able to support a transparent background, this may also be used to make logos for a

webpage etc.

PNG

BMP or also known as bitmap image file or device independent bitmap (DIB) file format, is a raster graphics

image file format used to store bitmap digital images. Most BMP files are quite large due to a lack of any compression. They are capable of storing 2D digital images of arbitrary

width, height, and resolution, both in either monochrome or colour. Due to these files losing quality when scaled as they have a low resolution, so are usually put on the internet as a JPEG or GIF file because this increases the loading time considerably. Microsoft Windows uses BMP a lot, images

saved in Paint are usually BMP files but are then compressed to a JPEG or GIF file as they are too large to be

used on the internet.

BMP

RASTER S/W AND VECTOR S/W

Left: Raster/ Bitmap (.jpg .gif .png) Right: Vector (.svg)

Left: VectorRight: Raster

The main difference between Raster and Vector Images is that Raster

images are a dot matrix data structure representing a generally rectangular

grid of pixels, or points of colour, viewable via a monitor, paper, or other display medium whereas vector images

are made of a thing referred to as ‘paths.’

Raster files formats are GIF or JPEG, these file formats are made of pixels of different colours, whereas a typical vector file format would be EPS and BMP files, these files are composed of paths and lines that are

either straight or curved.

File conversion, or also known as data conversion is the conversion of computer data from one format to another.. Files can be encoded in a variety of ways , and in many

different file formats.

A file may need to be converted for use in another programme or computer or for a different purpose than it

was originally made for, and so file conversion is necessary for the file to be used in a different way. Some conversions

are much more difficult than others, converting a 24-bit PNG to a 48-bit one does not add information to it, it only pads existing RGB pixel values with zeroes, the conversion makes it possible to change a pixel to have a different value

but the conversion itself does not do that, only further manipulation of the image can.

FILE CONVERSIONS

Data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original

representation. The process of reducing the size of a file is referred to as data compression, although its formal name is source coding.

Compression can be either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy,

so non of the information of the file is lost using this method.

Lossy compression reduces bits by identifying unnecessary information and removing it, although the lossless method is more

commonly used and preferred.

Lossless compression usually results in a folder called a ‘ZIP file’, A .ZIP file may contain one or more files or folders that may have

been compressed. The .ZIP file format permits a number of compression algorithms.

COMPRESSION

http://en.wikipedia.org/wiki/Raw_image_format

http://en.wikipedia.org/wiki/JPEG

http://en.wikipedia.org/wiki/GIF

http://en.wikipedia.org/wiki/Portable_Network_Graphics

http://en.wikipedia.org/wiki/BMP_file_format

http://en.wikipedia.org/wiki/Data_conversion

http://en.wikipedia.org/wiki/Data_compression

http://en.wikipedia.org/wiki/Zip_file

BIBLIOGRAPHY