Graphical File Formats
We have many different types of graphical file formats and this is because of the different types of images that we many have.
Some file formats that we use for graphics such as images etc are as follows;
J-Peg, GIF, BMP, PDF, PSD, PNG and TIFF.
Each of these above have different uses and also each of these may also give different files sizes and the quality of the file (image) may also change better or become worse.
The j-peg format may be the most common when saving images and receiving image from the web or through e-mail and this can be seen when looking at images on the web.
The GIF file format is also used quite frequently however this may be for images as a near cartoon like affect. Animations and cartoon images are usually saved as a GIF file and this is because if you convert a j-peg, for example, to a GIF file then this may actually change the image slightly and if you look and study the image closely you can see the change and the animated like affect on the image.
The file size of the j-peg image does increase when changed to a GIF file as you can see in the screen shot below. I have included different types of file sizes in this list and the two highlighted are the two explained.
Bitmap Graphics:
Bitmap graphics are the most common graphics used on the web and most images that you see on the web are a bitmap.
Bitmap graphics are made up of pixels which each contains colour information. A pixel is minutely small. One image may contain thousands of pixels and even hundreds of thousands of pixels. These can only be seen when the image is magnified. A graphic composed with thousands of pixels its own colour will obviously be far better quality. This may be good for images such as photographic images etc.
Therefore the more pixels on the image, the better quality the image will be. Bitmap images/graphics are a large file when saved, the quality can be distorted when enlarged or changed in size, they can be created when out onto the PC using a scanner and a digital camera and they are ideal for screen shot etc.
One very good and popular bitmap drawing software is Adobe Photoshop. This is explained in depth in my hardware write-up in task A.
Vector Graphics:
Vector graphics are different because as bitmap is composed by pixels, vector graphics are created with lines, points and curves and when put together can create complex images. These can then be filled with gradient and solid colours. These are created using mathematical codes and sequences (Mathematical creations).
If a vector graphics was to be re-sized then this would actually be re-produced to a different size, therefore this is how a vector graphic would not lose any quality when re-sized. This is one of the key differences between vector and bitmap.
Therefore as this is an advantage, vector graphics are ideal for creating logo etc, as these will have to different sizes to suit the document or publication that it is being created on. For example, a rather small company logo created by vector would be suitable for a letter head document, although a large logo would be needed for a banner or billboard for advertisement. The quality of the logo would not change.
Vector graphics are a small file when saved, there is no loss of print quality when changed in size, and they are very good for when creating diagrams and they are made from shape and objects such as triangles and circles.
One very good and popular bitmap drawing software is ‘CorelDraw’.
The Benefits and Limitations of Vector and Bitmap Graphics:
There are a few main differences between the two graphic types and I have mentioned then briefly above however I will explain these now.
First the file sizes are quite different. We see a small file in vector graphics and a large file for bitmap graphics and these are even larger when pictures contain large colour depth.
We can scale vector graphics to any size with losing any of its quality however when we re-scale a bitmap graphic it will lose quality and become ‘fuzzy’ like.
The user create a vector graphic using the mouse or maybe a graphics tablet and on a specific drawing software application whereas a scanner or digital camera is used to create a bitmap graphic as it is a image or photograph etc.
As I’ve mentioned bitmap graphics are good for photograph and images etc, whereas vector graphics are used for diagrams etc.
File Compression:
Compression is the reduction of the size of data in file etc in order to send throught email etc on our computer. When a file is compressed it can take much quicker to send rather than an un-compressed file.
When sending a graphical image we should compress the file, using a program that uses a formula to compress, as these file do tend to become large in size. Therefore this would take time to send.
The print screen below shows two folders. The folder that is highlighted is compressed. The other is not compressed. The sizes of the will be different as the compressed folder is compressed therefore this will be smaller in size.
There are two main types for compressing files. These are; lossy and loseless.
Lossy Compression:
Lossy compression is when the data in the file is compressed and from this some of the data would be lost. Therefore if an image uses lossy compression the quality of the image may be reduced slightly. This can also be completed on audio files, video files etc. The reason for this is that it the multimedia type can to be sent through email etc from our computers more easily. One type of file format that uses lossy compressions is the well-known J-PEG.
Lossless Compression:
The other main file compression is loseless compression. This is actually the complete opposite of lossy compression.
Data does not lose any quality in the compression process. As lossy works with video, images etc. lossless works with text files such as word processing documents, publications etc.
For lossless compression the data can be packed to a small file size.
The lossy compression can produce a much smaller file size than the lossless compression.
Advantages of file compression is that there will be more disk space, there will be much faster reading and writing on the hard disk and the file transfer will be much more quicker and therefore efficient.
Disadvantages are that there are unknown pixel/byte relationship, a decompression process will have to be performed the retrieve all previous data and there is added complications such as not having the best quality of an image for example if using the lossy compression.
Image Resolution:
Image resolution shows the detail that an image holds. This would apply to digital images, film images and also any other type of images such as still images etc.
Higher resolution means that there are more pixels in the image, which obviously means that the image will look cleaner and higher quality.
On a PC monitor the screen is made up of thousands of pixels. This is then given a code. We hear of 1024x768 etc. Well this is the resolution as there are 1024 pixels horizontally across the screen and then 768 pixels up the screen. This is how we get the code and the resolution of the screen.
The first image below shows dots per inch and pixels per inch on an image and the second image shows what uses the different types of resolution.
· dpi - dots per inch
Colour Depth:
Colour depth is basically details of the number of colours used in a complete image.
The higher and more colour depth that there is in a single image, then the more that the image will look realistic and it will be of good quality.
And also with bitmap images, the chosen colour depth will affect the size of the file.
There are different types of colour modes within colour depth.
I have shown two different types of image files below to show the difference in colour depth. The two types that I have included are j-peg and then a gif image. These images are obviously the same as you can see from below. I have included two the same purposely to explain how differernt file formats can change the detail in file colour depth as well as the actual quality of detail of the image.
Have a look at both images really closly ans study the images and you will see the difference between the two because of the difference in file format.
Have a look at both images really closly ans study the images and you will see the difference between the two because of the difference in file format.
You can see the differences between the two as the gif. image gives a sort of animation look to the image while the j-peg gives the real effect as we see from the colour depth and also the resolution and quality of both images.
Monochrome is black and white colours. This has the least amount of storage requirement. There are just 8 pixels stored in one Byte.
Greyscale which is 256 shades of grey colour and because a byte can be one of the 256 shades, then each pixel has one byte of storage each.
Colour depth has also16 bit colour which is high colour, 24 bit colour and 32 bit colour which are true colours.
This report has explained how different types of graphic images relate to file formats and also I’ve discussed the impact that file format, compression techniques, image resolution and colour depth have on file size and image quality.
I hope you have found this report informative and thank-you for taking the time to read it.
Thank-you!
