Digital Graphics File FormatsJoseph Headford

The Two Types of Graphics

There are two main graphic types:⁻ Raster⁻ VectorThese terms refer to the way in which an image is built up and represented on screen.

Raster Graphics

Raster Graphics are represented by bitmaps. Bitmaps are made up of pixels (bits) and each individual pixel records the colour information for that specific section of the photo. For example when a camera has a 15 megapixel sensor, it is referring to how many million pixels each photo is broken into. E.g. 15 megapixels represent 15 million pixels. However, because the image is made of individual pixels you cannot scale the photo without losing definition and quality, unlike vector graphics.

Vector Graphics

Vector graphics are made up of paths, which are defined by a start and end point, along with other points. They can be used to make curves, and angles in between the start and end points. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams.Because the graphic is not made up of a grid of coloured pixels it can be scaled up and down without any loss of definition. This means that the image can be used for anything from a company card to a billboard.

Raster Graphics

JPEGStands For Joint Photographic Expert Group

Used For/Example JPEG is a lossy compression technique used mostly in photography and is the format predominately used by camera’s to store the photos. It has a relatively small file size, however this is a trade off for image quality.

Advantage Because the file has up to a 70% compression it is not very big and allows for a fast transfer time between devices and quick downloads. Also because of the compression JPEGs of perfect for use on website and small applications (such as business cards). JPEG being a universally accepted file type is also compatible with almost every digital device and computer available and does not require specialist software to open.

Disadvantage With each edit as the image is uncompressed and recompressed the definition is lost. With each edit this will be gradually more evident.

TIFFStands For Tagged Image File Format

Used For/Example TIFF is a popular file type with graphic designers and for image archiving and can be edited and resaved without losing image quality.

Advantage File size can be reduced in a multitude of ways such as TAR and ZIP without any heavy loss in image quality as well as lossy compression techniques like JPEG. It’s a format recognised by most computers, and is cross compatible across with both MACs and PCs. They can also save multi-page documents meaning that is ideal for use by magazine and newspaper producers for multi-page editing.

Disadvantage Because of the large file sizes each photo is high quality but also takes up much more space than a compressed file and high spec equipment is needed to process each image. Most websites and galleries also do not support the TIFF file type. Transfer times can also be large because of the file size.

GIFStands For Graphic Interchange Format

Used For/Example GIFs are short digital animations that consist of a few still images that run one after another in a continuous loop to create the appearance of a video (much like a flick-book). They are more often than no found on the internet.

Advantage GIFs, when used online, are a good and sometimes entertaining way to quickly portray information to users. This is because unlike a video GIFs require no interaction to begin playing as they do this automatically upon loading. They also because of their simplistic nature and small file size do not take long to load. GIFs are also very easy to make and do not require much time or effort to create. They are often used on sites such as Buzzfeed News, Tumblr and Reddit.

Disadvantage Images can sometimes look pixelated because f the increased compression and limited colour pallet available. Also much like a JPEG, once saved you are unable to edit a GIF any futher.

BMPStands For Bitmap Image File

Used For/Example Bitmap files are best suited for the storage of real-world images. Intricate images can be rasterized along side video, scanning, and photographic equipment and stored in a bitmap format. This format is a very similar to TIFF and JPEG files.

Advantage BMPs main advantage is that there is not loss in definition (image quality) with compression and recompression.BMPs can also be converted into both TIFF and JPEG files to help reduce the file size, and no specialist software is needed to open this file type.

Disadvantage However the actual file size is usually very large because of the minimal compression utilised by this file type. Also, this image type does not scale well much like the previous three raster graphic file types.

Vector Graphics

PSDStands For Photoshop Document

Used For/Example This is a specialist file type utilised by the photo –editing software ‘photoshop’. It acts as a way of saving photoshop projects without risk of losing your previous work or having to compress the file and reduce the definition quality of the image.

Advantage It allows the storage and future editing of projects currently being worked on. It will also record and save all changes made small and large without any loss to definition as the file is not compressed.

Disadvantage PSD files can be extremely large, because these lossless images use no compression. This preserves all image information, but can make the file itself difficult to email or transfer. PSD can also only be opened by specialist software such as Photoshop or specifically designed software.

AIStands For Adobe Illustrator Art

Used For/Example This file type is used by the drawing programme Adobe Illustrator for more precise drawing and image creation than other photo editing software can do. This is optimised with the use of a digital graphics tablet such as the Wacom Intuos Tablet (http://www.wacom.com/en-gb/products/pen-tablets/intuos-pro-medium).

Advantage This file type supports specialist graphical elements. Also because the graphics are built up of vectors it allows scaling without any loss of definition in the image. Because of this it is perfect graphic type for use in logos and large images.

Disadvantage Special software is needed to open and edit this type of file.

FLAStands For Flash File

Used For/Example Flash files can create a games and animations in Adobe Flash.

Advantage FLA files have a very small file size but a high quality that can contain video and audio; this mean they are optimal for use on the websites as they load quickly.

Disadvantage Only some software can actually open flash files and only browsers that support flash (either have Adobe Flash integrated or added on) to play flash files.

WMFStands For Windows Metafile

Used For/Example WMF’s are usually used for company logos and graphics such as Windows Clipart.

Advantage Because WMF’s are made up of both vector and bitmap graphic components they can be scaled up with no loss in definition.

Disadvantage However this type of file is only available on Windows so they are not universally available.

File Format Capture and Optimising

CompressionDefinition Compression, specifically lossy

compression, reduces the overall size of a file by reducing the amount of information saved.

Advantage Compression allows more files t be stored on a hard-drive be each individual file doesn’t take up much space.

Disadvantage However the main disadvantage is that with compression images lose definition and seem to be more pixelated as less pixels are used in the compressed image.

Image CaptureMethod Scanner

How is it used for image capture of graphics

Scanners are used to take physical images and digitise them into images ready to use on the computer. For example a physical drawing could be used in Photoshop or Adobe Illustrator as the basis for a high quality image.

Method CameraHow is it used for image capture of

graphicsA camera is arguably the most common way to capture the physical world in an image. As light enters the camera lens it is captured by a sensor and recorded and displayed as a digital image.

Method Graphics TabletHow is it used for image capture of

graphicsA graphics tablet allows you to control the cursor of a computer with a pen. This means that more precise movements can be made for illustrations and other detailed images.

OptimisingWhy would you optimise? Optimising is when files are specifically

adjusted to make them more accessable and less demanding for more people. For example images on the web are optimised to reduce loading times and easy viewing.

How can you optimise? Images that are intended for use on the web can be optimised by reducing the file size and image size; reducing the bit depth (colour pallet) and compressing files.

Advantage to optimising By reducing the file sizes, images download faster and files can be transferred more easily.

Disadvantage to optimising Optimising can reduce the quality and definition of an image.

Storage

File SizeWhat could affect a Working Scale (Photoshop) document file size?

If you had many layers or a multi-page document this would dramatically increase the overall file size.

How could you reduce the file size of a Working Scale document without

affecting quality?

When in Photoshop you can select image size and then by replacing ‘Bicubic Automatic’ with ‘Bicubic Sharper’ as this is best for reduction. Then you should reduce the image size, by no more than half. This will reduce the file size dramatically without loss of image quality.

What is an advantage of scaling up images before exporting?

By scaling up an image before exporting it into a file type such as JPEG you are countering any quality that might be lost because of compression.

What is a disadvantage of scaling up images before exporting?

You could lose some of the images quality if it included a variety of bitmap style graphics as these will lose definition when scaled up. Then along with compression this will dramatically lessen the quality of the image.

File Naming ConventionsWhat naming conventions could you use when creating your video game assets?

It is best to use a descriptive name that simply tells the reader at a glance what the file contains and what it is used for. A good example used by http://www.gamasutra.com/ is that a filename “bigboss1.obj” is not very descriptive, while "final_boss_lvl_01.obj" is surely better.

Why is it a good idea to accurately name your assets?

If a file is not named properly certain game assets may not be utilised or found when needed. However if all files are not named under the same conventions this can cause confusion. Therefore you must accurately and consistently name files under the same conventions to simplify finding files.

Asset ManagementWhy would you use folders when storing

your assets?Folders provide a way to easily store files are similar types together. For example when organising game assets you could place all character models in one place and all sets in another meaning that they are all together and easy to find when required.

What folders would you create and what would you save within them

For a game I would have character models within a specific folder and then have subsections to organise enemies and lead character models. I would then organise set pieces and visual assets into their own folder as to provide an easy way to navigate the files and find those that are needed.