1. 2.01 Investigate graphic image design.
Raster Graphics
2.01 Investigate graphic image design.

2. Raster Graphics Also called bitmap graphics
Consist of grids of tiny dots called pixels
Have a fixed resolution and cannot be resized without altering image quality
Edited in paint programs
Teacher Note: Enlarging raster graphics causes them to become pixelated (you can see the individual blocks of colors that make up the image).
Notice the pixels
Bitmap enlargement
Image source:

3. Common Raster Formats
GIF
JPEG
BMP
PNG
TIFF

4. GIF – Graphics Interchange Format
Animation – Standard format for animation on the Internet.
Transparency – yes
Lossless compression
Colors = 256 (8-bit)
Most common format for:
Text
Clip art, animations, icons, logos
Simple diagrams, line drawings
Graphics with large blocks of a single color
Graphics with transparent areas
Images displayed on computer screens and on websites.
Animated Gif

5. JPEG – Joint Photographic Experts Group
Commonly Used For:
Desktop publishing photographs
Photographs and natural artwork
Scanned photographs
ing photographs
Digital camera photographs
Animation – No
Transparency – No
Lossy compression
Colors – 16.7 M (24-bit)
High quality but larger file size than a GIF
Teacher Note: This format is best for images containing many colors or shades of color. Most digital cameras save the images made with the camera as JPEG files on their memory cards.

6. BMP - Bitmap Commonly Used For: Animation – No Transparency – No
Editing raster graphics
Creating icons and wallpaper
On-screen display
Animation – No
Transparency – No
Uncompressed
256 colors
Large file size - not well suited for transfer across the Internet or for print publications
Teacher Note: When editing images, all the changes would be made to the BMP file. When the user is satisfied with the final image, they would then save the BMP as a different file format depending on their intended use of the image. (For example, if it will be used on a website, the images would be saved as a compressed file format such as GIF or JPEG.)
By on-screen display, this means displayed on the monitor but is referring to images that are on the desktop computer, not from Internet websites.
Icons

7. PNG – Portable Network Graphics
Animation – no
Transparency – yes
Lossless compression
256 colors
Not suited for photographs
Commonly Used For:
Replacing GIF and TIFF images
Online viewing of images
See examples at
Teacher Note: Browser software or image editing program may require the user to download a plug-in before recognizing or opening the file.

8. TIFF – Tagged Image File Format
Animation – No
Transparency – No
Available in compressed and un-compressed formats
Compressed is advised
Colors – 16 M (24-bit)
Commonly Used For:
Storage container for faxes and other digital images
To store raw bitmap data by some programs and devices such as scanners
High resolution printing
Desktop Publishing images
Teacher Note: TIFF images have very high quality which is ideal for faxes or printed images, such as those used in desktop publishing. However, this results in a large file size so it is not recommended for images that will be viewed over the Internet.