File Types and Formats Blog Notes

 Image Properties

Pixel

A pixel is a single dot of an image. An image is composed of loads of pixels.

This is an image

This is the equivalent of a pixel (couldn’t go any smaller). This represents the bottom corner of the image and the image has hundreds of these.

Image Resolution

Image resolution is how many pixel there are in an image, a picture that only has 10x10 pixels is good quality but very small if we make this picture bigger the image becomes pixelated because it adds pixels you are adding pixels that don’t exist but if you had an image of 50x50, the image could be seen better at bigger size because there are more pixels to use.

This image shows the difference between the amounts of pixels used as you see a 10x10 is small and if made big is blurry and a big picture that has more pixels made bigger is only partially blurry.

Pixel Colour Intensity

It is the amount of colour used in the image. So if an image is in RGB format the image colour intensity is the amount of red, green or blue used in the image. Each colour is represented in black and white with black being more intensity of that colour and white being less intensity.

 

This is an image with lots of colour

 

This is the red channel which shows the amount of red used (more red intensity is black and less is white and the grey colour is the middle between the 2)

 

This is the same as the last but with Green

Same as before but with blue

Types of Pixel Colour Intensity

There are 2 different colour intensities:

RGB: Red, Green and Blue this type of colour intensity is good for digital use like looking at it on a PC or camera.

CMYK: Cyan, Magenta, Yellow and Key (Black) this type of intensity is good for printing.

Compression

When we compress something this becomes a lot smaller in file size so that it doesn’t take up as much space on our hard drives. There are 2 different types of compression used in images which are Lossy and Lossless

A lossy compression is when an image is reduced and the pixels that aren’t needed in the smaller file are deleted. The data that has been deleted can’t be recovered so it can’t recover its original size. Lossy compression are good for big detailed pictures because they reduce the amount of pixels in the image which reduces the data usage on your hard drive.

Lossless compression saves the pixels away so the image can be made bigger and smaller without the picture becoming pixelated. Lossless compression is good for logos that need different sizes (logo on front of building big, logo on a piece of paper small or on a call card which is really small).

Types of digital graphics

Raster Image

A raster image is an image made of pixels and each point of the image is saved as a colour. We would use this type of images for posters or other big drawing that use lots of colours. When we zoom in on the image is because pixelated (because it’s made of pixels) this way it is only good to use to an image that has a fix size and doesn’t need resizing. This makes the files smaller. 

Some of the Raster image formats are: JPEG XR, TGA, ILBM, IMG, PGF, etc.

BMP

Introduced on Windows platform. Commonly used raster graphic format for saving image files. The BMP format stores colour data for each pixel in the image without any compression. A 10x10 pixel BMP image will include colour data for 100 pixels. This method of storing image information allows for crisp, high-quality graphics, but also produces large file sizes. The JPEG and GIF formats are also bitmaps, but use image compression algorithms that can significantly decrease their file size. For this reason, JPEG and GIF images are used on the Web, while BMP images are often used for printable images.

Uses lossless compression.

Can’t hold transparency or animation.

GIF

Designed by CompuServe in early days for computer 8-bit video, always uses lossless LZW compression, but uses an indexed file (8bits, 256 colours maximum), very good for web graphics, one colour in indexed colour can be marked transparent, allowing underlaying background to be seen, doesn’t save the dpi number for printing resolution, supports animation showing several sequential frames fast to simulate motion.

Tiff

This file format is lossless which means the image doesn’t get pixelated when zoomed on. It has the highest quality format for commercial work. Lossless compression. From 1-bit to 48-bit colour. It does support transparency but it can’t hold animation. This file format is good for graphic artists, publisher industry and photographers because it has the highest quality image format.

Versatile, many formats supported.
Mode: RGB or CMYK or LAB, and others, almost anything.
8 or 16-bits per color channel, called 8 or 16-bit "color" (24 or 48-bit RGB files).
Grayscale - 8 or 16-bits,
Indexed color - 1 to 8-bits,
Line Art (bilevel)- 1-bit

JPG

The file is much small than other standards because it uses lossy compression which means we get smaller files but a the cost of quality. Good for web pages, email, memory cards, etc.

RGB - 24-bits (8-bit color),
Grayscale - 8-bits

Can’t hold transparency or animations.

This type of image is used in most cases for its small file sizes and is easy to carry around lots of images like for photos.

Vector Images

A Vector image is an image where the image is made of shapes and each bit has coordinates saved to it so when we zoom in on the image it recalculates the coordinates so that the image stays the same and we don’t get a blurred pixelated image. This type of image is good for logos because we need the logo big on the front of a building or a small calling card and using the type we can make 1 logo and just resize it. This type of image uses a lot of memory because it keeps the colours doesn’t matter the size.

Some of the Vector image formats are: XPS, PPT, VML, AI, CDR, .dwf, .dwg, etc.

PSD

This is the Photoshop standard that is one of the few formats that supports all of Photoshop’s features. File size can be very large if we are working with lots of layers. Can be reopened and modified if needed.

It uses lossless compression

It can hold transparency but not animation.

This file format is used for making and modifying anything in Photoshop or InDesign programs.

Fla

Fla is the adobe flash standard that lets us modify the images in flash. This format is similar to photoshop because it uses lossless compression and holds the layers like PSD but can also use animations unlike PSD.

Ai

Ai is adobe illustrator file format that lets us make vector images.