• Pixel
The term pixel is actually short for Picture Element. These small little dots are what make up the images on digital. The screen is divided up into a matrix of thousands or even millions of pixels.
Each pixel can only be one colour at a time. However, since they are so small, pixels often blend together to form various shades and blends of colours. The number of colours each pixel can be is determined by the number of bits used to represent it.
Colour Depth
1 bit colour 4 bit colour 8 bit colour 24 bit colour |
No. Of Colours
2 16 256 16,777,216 or True Colour |
1 bit colour
4 bit colour
8 bit colour
24 bit colour
Determining Colour Depth - Since each bit represents 2 colours, it is easy to work out the number of colours for the various colour depths. The number of possible colours would be 2 to the power of the number of bits per pixel:
A colour depth of 4 bits would be 2 times itself 4 times: 2 x 2 x 2 x 2 = 16 colours
A colour depth of 8 bits would be 2 times itself 8 times: 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 colours.
A colour depth of 24 bits would be 2 times itself 24 times: 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 16,777,216 colours
There are several established colour models used in computer graphics, but the two most common are the RGB model (Red-Green-Blue) for computer display and the CMYK model (Cyan-Magenta-Yellow-black) for printing.
• Resolution
Put into some very basic terms, resolution is the quality of the image. As the resolution goes up, the image becomes more clear. It becomes sharper, more defined, and more detailed as well. Why is that? Because there’s more information in the same small space. Your computer, laptop and your smartphone (if you’re lucky enough to have one) both have image resolutions. There is a certain number of dots in the space that is the screen. Put even more simply, the more dots you jam into the width and height of the screen, the higher the resolution. The less dots, the lower the resolution.
| Number of Megapixels | Image Dimensions | Acceptable Print Size (Inches) |
| 2.0 | 1740 x 1160 | 4 x 6 [standard] |
| 3.0 | 2160 x 1440 | 5 x 7 |
| 4.0 | 2450 x 1633 | 8 x 10 |
| 6.0 | 3000 x 2000 | 9 x 12 |
| 8.0 | 3504 x 2336 | 9 x 12 |
| 10.0 | 3872 x 2592 | 10 x 15 |
| 12.0 | 4256 x 2832 | 11 x 17 |
| 14.0 | 4608 x 3072 | 12 x 18 |
| 16.0 | 4928 x 3264 | 16 x 20 |
| 18.0 | 5184 x 3456 | 16 x 20 |
| 24.0 | 6016 x 4000 | 20 x 24 |
• Anti-aliasing
Anti-aliasing is the process of smoothing the jagged appearance of diagonal lines in a bitmapped image. The pixels that surround the edges of the line are changed to varying shades of gray or color in order to blend the sharp edge into the background.
This refers to the proportions of the screen you are working with, whether a flat-screen TV or Smartphone.
• Raster Images: file formats and uses - psd, bmp, gif, tiff, jpg, png
Raster images are more commonly called bitmap images. A bitmap image uses a grid of individual pixels where each pixel can be a different colour or shade. Bitmaps are composed of pixels.
•Vector Images: file formats and uses - eps, wmf, fla, svg, ai
Vector graphics use mathematical relationships between points and the paths connecting them to describe an image. Vector graphics are composed of paths.
• Cross-platform Images: format and uses - pdf
Adobe® Portable Document Format (PDF)
The Adobe Portable Document Format (PDF) is used for publishing electronic documents to be distributed over the Internet and other online services. The advantages to PDF files are:
1. Their compact size...making them ideal for distributing product brochures and technical manuals over the Internet.
2. They are platform independent - they work with both Mac® and PC computers.
3. The software used to read and print them is free.
4. They display and print using the PostScript® page-description language. That means if line art is embedded as vector objects, it will display and print perfectly at any size or resolution. Plus it can be extracted and placed into illustration documents or bitmap images.
5. Fonts are embedded within them so the target computer does not have to have the fonts installed to view them.
6. They are fully searchable.
7. They can contain hyperlinks to pages within the PDF document itself or to a web page on the Internet - or to movie clips.
8. They contain PostScript® data and can be imported into both image editors and illustration programs just like EPS files.
9. Vector art contained in the PDF file will make PERFECT printed output at any resolution - just as if the output were being printed from a job saved as a PostScript .PS or .PRN file. If there are embedded bitmaps they will usually be downsampled to 72 pixels per inch for viewing on a monitor or for transporting over the Internet. This is to keep their file size small. However, bitmaps can be embedded at high resolution for high-end output.
10. The PDF file format is ideal for distributing online brochures and technical documents.
• Compression - lossy and lossless
Compression is the process whereby a file is squeezed into a smaller parcel for storage or transmission. There are two types:
Lossless Compression
Whether a file is being stored or transmitted, once opened again, lossless compression recreates a the file as an identical match to its original form. All lossless compression uses techniques to break up a file into smaller segments. With lossless compression, every single bit of data that was originally in the file remains after the file is uncompressed. All of the information is completely restored.
Lossy Compression
Lossy compression works very differently. These programs simply eliminate unnecessary bits of information, tailoring the file so that it is smaller. This type of compression is used a lot for reducing the file size of bitmap pictures, which tend to be fairly bulky. When the file is uncompressed, only a part of the original information is still there (although the user may not notice it). Lossy compression can't be used to compress anything that needs to be reproduced exactly
• Image Capture Devices – scanner, digital camera, tablet/smartphone
Regardless of the type of device, in order to capture raster imagery a lens has to be used.
• Optimising
Image optimisation takes place to prepare the artwork for its final use. This could involve, resizing, altering resolution, cropping, changing the file format ad colour model and all depends on what the image is being used for. It is essential to remember that the final outcome will need to be considered from the start of the design process, otherwise options may be limited.
• Storage and Asset Management
The storage and organisation of artwork is crucial, both in terms of working efficiently and securely. Sloppy security can lead to designers having work stolen or being in breach of contract with clients. Work is now stored in a variety of ways; locally using hard-drives, portable drives, CD and DVD and cloud-based storage systems.
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