LESSON 01 – REVIEW OF BASICS

Your teacher will give you a demo on the specified topics related to Photoshop. In this content page, we will look at the different image formats.

IMAGE CLASSIFICATION

There are several ways of grouping or describing images.

A) PHOTO VS CARTOON

One way involves splitting all images into three groups – photos, cartoons & hybrids (combination of both). A photo image is simply an image that is taken using a camera or scanner. A cartoon image is an image that is created on the computer. A hybrid is an image that contains a part that is a photo and another part that was created on the computer.

Photo

Cartoon

Hybrid

From the perspective of the computer the important difference between a cartoon and a photo is that a cartoon tends to have more pixels that have the same colour while a photo has a lot more colour variation from pixel to pixel. The more colour variation a cartoon has, the more it tends to look like a photo.

B) RASTER VS VECTOR

The little dots that make up an image are called pixels. In raster images, each pixel is assigned a specific colour. We use raster images because it is easy to create them using a camera or a scanner. The opposite of a raster image is a vector image. Vector images are generally simpler images that can be explained in terms of different mathematical objects such as lines and circles.

Raster Images

• PRO – Very common, Used everywhere on the internet
• PRO – Easy to acquire using camera or scanner
• CON – Quality will change when the image is resized or zoomed in/out.
• OVERALL – Most images that you will see in this course will be of this type.

Vector Images

• PRO – The image is redrawn whenever it is resized. So, the quality is always perfect at any size.
• CON – Cannot represent very complex image (such as photos).
• OVERALL – Vectors are the best for logos and other similar graphic designs.

Source: Wikipedia Commons

C) IMAGE FORMATS (RASTER FORMATS)

We can also classify images based on their file format. The most common formats for raster images are BMP, JPG, GIF and PNG. Your digital camera probably uses the JPG format. Some use a rarer format called TIFF.

The most common types of vector image formats are SVG, VML & AI.

In this unit, we will only focus on the raster image formats.

BMP

• Called “bitmap”
• PRO – Perfect storage quality for all image types
• CON – Massive file sizes
• CON – Not fully supported on the internet.
• OVERALL – Use to temporarily store images perfectly.

JPG

• Pronounced “Jay peg”
• PRO – Small file sizes
• PRO – Stores Photos in practically perfect
• CON – Storage of cartoons usually leaves considerable imperfections (see below)
• OVERALL – Use on photos only. You can use on cartoons if you don’t plan on editing them again.

GIF This cartoon image was initially a GIF. You can see that the colours are all perfect looking.

JPG Once the image is stored as a JPG, you can see the addition of small artifacts. These artifacts are practically impossible to see in photo images.

GIF

• Pronounced “Jiff”
• PRO – Lossless compression for images that have 256 colours or less
• PRO – Supports animation
• PRO – Supports transparency
• PRO – Small file sizes
• CON – This format is patented. So all companies that create software that uses the GIF format have to pay a royalty fee.
• CON – Nowadays, most images (all photos and many cartoons) contain more than 256 colours. Storing such images as GIFs will create a snowy effect on the image.
• OVERALL – Use for cartoons with low amount of colours. Use for tasks requiring animation and transparency.

JPG This cartoon image is saved as a JPG. If you were to zoom in, you would be able to see little artifacts. However, it’s still better than GIF because there are more than 256 colours.

GIF Once saved as GIF, you can see the snowy effect in the image. This is a major flaw for the GIF format. The same occurs in photo images.

PNG

• Called PNG.
• This format is suppose to replace the GIF format. Some suggest that PNG stands for “PNG’s not GIF”.
• PRO – Lossless compression of all images
• PRO – Small file size.
• CON – Now fully supported by all new browsers. The older browsers don’t support it.
• OVERALL – Use for all images that contain cartoons.

DID YOU KNOW

Perhaps the most important property of digital cameras is their mega pixel rating. This characteristics tells you how many million pixels will be used to store an image. So, a six megapixel camera will use 6 million pixels to store a photo while a 12 megapixel camera will use 12 millions pixels.

1 megapixel = 1 million pixels