File size and image quality Gladys Nzita-Mak Unit 30 - D2

Bitmap formats chosen: BMP JPG PSD GIF PNG Unit 30 - D2

Vector formats chosen: FLA SWF Unit 30 - D2

Compression techniques Compression is done when a file, in this case an image is taken and compressed into a file format making the image smaller. For example a good quality image saved in a JPEG can be saved and compressed into another image file format such as GIF, and once saved the image will have differences compared to its original image it was saved in previously, such as it may look pixelated when zoomed in due to the fact that it is now a smaller image and will even be saved with less memory compared to its previous file format. Lossless compression Lossless compression is a compression technique with happens when a file format such as a picture, is compressed from one file format to another and once compressed and is lossless, no data from the file which has been compressed will be lost. An example of lossless compression is the file format PNG. PNG file formats have been created to use lossless compression whilst saving images, compressing images with all no loss of data keeping it exactly the way it is intended to be (and look). Lossy compression Lossy compression is a compression technique which compresses images into a lower quality file size, which is visible as pixilation in the image is seen compared to the image it was before it was compressed. Therefore once compressed lossy the file size will be smaller. The best file format for a picture to be compressed is the JPG format. The reason for this is because as it compresses images in lossy compression, it saved images with good quality and colour, and only loses about 5% of its image which is barely noticed, still leaving an overall good quality image. Unit 30 - D2

Image resolution This is the detail within an image. In image files that are saved with higher resolution means that the image will look more crisp and with better quality, and are usually saved with higher amounts of memory, whereas with images that contain lower resolutions, the image will not look as good as images with better quality, and won’t take up as much space as higher resolutions will do. Resolutions are usually measured vertically and horizontally by pixels, for example they can be represented as “345x876”. Saving images with higher resolutions also means that the pixels in the image increases. DPI (Dot Per Image) which are the numbers of dots printed within an image consisting of hundreds of dots of colours making up an entire image, for example with a printer, it uses DPI when printing images. The more the dots in the image, the finer and sharper the image will turn out to be. Unit 30 - D2

Colour depth When an image has a lot of colour and detail in it, colour depth is the best term to describe it. Colour depth is the amount of colours that are used in an image. Images with a high amount of colour depth are images that will contain large amounts of colour and detail. Colour depth is represented in “bits”. Unit 30 - D2