Mr Tim's Graphics Primer


Update: 01-08-2014. This set of articles are one of the oldest on my website written back in 2000 but the information is still relevant and useful. Given the speed of the modern Internet there is not much talk about image compression but it's amazing how many times the subject still comes up. Ever wonder why pictures on Facebook or the Ipad are not as good as you remember? Background picture compression. What bothers me is not that the pictures are compressed, but rather both services hide the fact. Hopefully this is a trend that will someday disappear. Until then I hope the following will give you an idea of how graphics and compression work.

If you do not currently have a good understanding of computer graphics and file formats I would highly suggest reading the articles in order. Most articles require concepts from the previous articles. At the end of the articles are various topics I have listed under the heading "support files". In the course of reading the articles I have referenced these topics as needed for people who may need further background information. These articles may be read in any order and I would suggest browsing the titles for any topic you may wish to refresh.

Note: If you are trying to understand how file formats and compression work, do be careful of Photoshop. Photoshop does not let you count or modify the number of unique colors in an image which is a major part of file compression. Also, some file options are not available in Photoshop. I would recommend programs like IrfanView, Paint Shop Pro, or any program that has both a "count color" tool and a "color depth tool". If all you have is Photoshop, use the "Save for Web" option which will give you more options saving GIF and JPEG files.

1. Overview
2. Bitmap and Vector Graphics
      Bitmap Images
      Vector Images
      Resolution and Scaling
3. Bitmaps In Detail
      The BMP format In Detail
      Bitmaps and the RLE Compression
4. Bits and the Number of Colors
      Bits and Binary Numbers
      The Number of Colors
      Bit Depth and the Number of Colors
      Other Useful Color Information
5. Reducing the Number of Colors
      How many colors do you need?
     Niagara Falls Image
           A Slight reduction in color
           24 bit to 8 bit
           BMP and GIF Formats
           Color reduction from 256 to 16 colors
           Images with no single primary color
     Balloon and Tower Images
           Images with No Single Primary Color
           Color Banding
     Random Examples
6. The GIF File Format
      Index Color Method
      Interlaced and Non-Interlaced
      A Final Word
      GIF Reference Article
7. File compression and Winzip
      File compression and Winzip
      LZW Compression
8. File compression and Data Loss
      "Lossy" and "Lossless" Compression
      Color Reduction
      Quality Reduction
9. The JPEG File Format
     Compression Method
           Text Description
           Important Points
     Examples and Comments
10. The TIFF File Format
Support Information
File Formats Quick List
Colors and the Computer
      The RGB Color System
      Additive and Subtractive Color
      Creating this in Adobe Photoshop
      Color Space and the Computer
Binary Numbers
      What's a Bit? Binary Numbers
Kilobytes, Megabytes, Gigabytes, O My
      How the computer calculates file size
File Sizes
      A File Size Comparison between BMP, TIFF, GIF and JPG.