Types of imageRaster, Vector and file extensions

What can you remember from last week?

• Raster• Vector• Compression• Lossy • Lossless

Types of digital graphics

• Vector images - Uses points, lines and curves- When scaled up there is no loss of

clarity- E.g: psd, wmf, fla, ai

• Raster images- Based on pixels- When scaled there is a loss of clarity- E.g: bmp, gif, tiff, jpgRaster

Compression

• Lossy- reduces the size of the file but also looses quality.

• Lossless- reduces the size of the file but the quality stays in tact.

Learning Aims:

• All of you will be able to discuss the different types of image

• Most of you will be able to research and make references to the different types of images

• Some of you will be able to criticise the use of different image types in graphics.

A Bitmap or Raster graphic• When you take a photograph

using a digital camera or scan an image from a magazine, you are creating a bitmap graphic.

• A bitmap graphic is composed of many tiny parts, called pixels, which are often many different colours.

A Bitmap or Raster graphic• It is possible to edit each individual

pixel.

• Since the computer has to store information about every single pixel in the image, the file size of a bitmap graphic is often quite large.

• When you resize a bitmap graphic, it tends to lose quality.

What are vector graphics?

• Vector graphics are created in graphics packages and consist of shapes called objects.

• It is possible to edit each object separately, for example, change the shape, colour, size and position.

What are vector graphics?

• Even if an object in a vector graphic is quite large, it doesn't need a lot of computer memory.

• Therefore the file size of a vector graphic is often very small.

• Vector graphics are scalable - ie when you resize them, they do not lose quality.

File Types used in graphics

• bmp, • png,• gif, • jpg, • Psd• tiff

Tiff files ending in .tif• stands for Tagged Image File Format.

• TIFF images create very large file sizes.

• TIFF images are uncompressed and thus contain a lot of detailed image data (which is why the files are so big)

• TIFFs are also extremely flexible in terms of color (they can be grayscale, or CMYK for print, or RGB for web) and content (layers, image tags).

JPEG (also known as JPG), file types ending in .jpg

• stands for Joint Photographic Experts Group

• JPEG files are images that have been compressed to store a lot of information in a small-size file.

• JPEG files are usually used for photographs on the web, because they create a small file that is easily loaded on a web page and also looks good.

• JPEG files are bad for line drawings or logos or graphics, as the compression makes them look “bitmappy” (jagged lines instead of straight ones).

What can you remember about GIFs?

• What does it stand for?

• Lossy or lossless?

• What is it mainly used for?

• Stands for Graphic Interchange Format

• compresses images but, as different from JPEG, the compression is lossless

• This format is never used for photography, because of the limited number of colors.

• GIFs can also be used for animations

PNG, file types ending in .png• stands for Portable Network

Graphics.

• It’s used almost exclusively for web images, never for print images.

• It also allows for a full range of color and better compression.

• PNG can retain it’s transparency

Psd, file types ending in .psd• Photoshop document

• These types of files are very large files allowing for large colour information.

• Usually images are retained in this format for print.

• These types of files are generally raster files, but there are some elements which are vector based.

.Ai file types

• Illustrator document

• Vector images

• Use large colour information

Bitmap graphics Vector graphics

What are they made up of?

What can be edited?

What is the file size?

What happens when they are resized?

How real do they look?

Native formats

Common file formats

Bitmap graphics Vector graphics

What are they made up of? Pixels of different colours Objects

What can be edited? Individual pixels Individual objects

What is the file size? Large, as the computer stores details of every pixel

Small, as the computer stores details of objects, which do not require much memory

What happens when they are resized?

They lose quality They do not lose quality

How real do they look? Real Not real (many of them look like cartoon images)

Native formats .bmp .svg

Common file formats .bmp, .dib, jpeg, gif, tiff, .png .psd

.cgm, .svg, .odg, .eps, .xml .ai

TASK: Write your article “What is digital graphics technology?”Research and explain using examples:

• Vector Graphics• Raster Graphics• Types of image• Advantages and

disadvantages of using different types of graphics.

• How Vector and raster graphics are created