Aim of this Tutorial:
In this tutorial I will show you how to use Corel PhotoPaint to produce highly optimized, bandwidth friendly, colour specific graphics for the WWW and for screen based multimedia. Many of the same techniques can be applied to print media images when colour reduction is required.

Contents
This tutorial is divided into the following sections:

PART 1 - Introduction

• Aim and Contents
• Introduction
• The central planks of Web graphics image optimization
• Three important aspects of Web image quality
• Example Images

PART 2 - Basic Concepts

• Image Resolution
• Colour
• RGB is for Screens
• CMYK vs. RGB
• Converting Image Formats

PART 3 - JPEGS 1

• JPEG Images
• Browser differences when displaying JPEGs
• Saving JPEGs and Layered Images
• The JPEG Export dialog box
• Figure 1 , Figure 2 and Figure 3
• Summary of important points when saving JPEG images using Corel PhotoPaint 8

PART 4 - JPEGS 2

• How to get the JPEG Results you want
• Figure 4 and Figure 5
• The final result
• Figure 6
• JPEG compression
• Figure 7
• A note of caution

PART 5 - GIFs 1

• GIF Images
• The GIF palette
• Additional stored information
• GIF Formats
• GIF File Size Issues - # of colours
• GIF File Size Issues - repetitive pixel data
• Real life GIF file size test in PhotoPaint
• Figure 8, Figure 9 and Figure 10
• Web page HINT

PART 6 - GIFs 2

• Problems with 8 bit colour display cards
• Dithering
• The Netscape palette - A special case
• Table 1 Web Safe (Netscape) Pallet Conversion Table
• Figure 11
• Broad compatibility

PART 7 - GIFs 3

• Converting images from one format to another - The Convert to Paletted (8 bit) Dialog box
• Figure 12
• Web-friendly 8-bit palettes
• The Adaptive palette
• The Optimized palette
• Netscape palette usage
• Using the Convert to Paletted command

PART 8 - GIFs 4

• Reducing the number of colours in paletted images
• The Optimized palette in detail
• Reducing the number of colours in Optimized palette images
• Controlling the preservation of colours during colour reduction
• Checking and changing the actual colours within a variable palette

PART 9 - Further Notes

• Several further notes on images
• Binary bingo
• Caveat carrot
• Farewell till next time

Aside Box , Glossary, Prologue (my personal ravings).

Most people use the WWW today via modems and thus bandwidth considerations are a primary concern. In addition, as the WWW is an open standard medium, a wide range of different computer systems can and are being used to view Web pages. Thus, reducing the file size of your images and using colours which the majority of computer systems can render are major goals for Web designers . However, in contrast to many traditional Web graphics design instructions, I will proffer an argument against the sole use of the so-called Netscape (216 colour) pallet for every image on your pages later in this article (see the aside box discussion).

The central planks of Web graphics image optimization.
The central theme to file size reduction for graphics used on the Web is to obtain the maximum reduction in file size while maintaining an acceptable image quality.
         

Three important aspects of Web image quality:

• The person viewing your images over the Web is unlikely to have seen the original image from which your graphic was created. Providing that certain features such as skin tones, natural objects (sky, clouds, trees, grass etc.) remain realistic, other colours or even the general colour tones and hues in your image may vary quite a lot from the original. (See examples 1a, 1b, 2a, 2b below) If graphic artists only ever produced 100% realistic images then life would be very limited indeed.
  
  
• Secondly, the acceptable image quality on the computer screen or on a web site may be quite different (often much lower) that the same image presented in print.
  
  
• Thirdly, every image is different and must be treated individually. Careful analysis of an image should reveal which format and colour range is best suited for that particular image. There is no single general rule which applies to ALL images. Some are more suited to one format that another. For some, the number of colours used can be massively reduced while others appear terrible when colour levels are reduced even slightly. (Refer here for some examples in different formats - (examples 3a-3d and 4a-4d).