How to Use Corel PhotoPaint 8 to Make Web-Friendly GIF & JPEG Images

Web Works Part 1 - Introduction

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.



This tutorial is divided into the following sections:

PART 1 - Introduction

PART 2 - Basic Concepts



PART 5 - GIFs 1

PART 6 - GIFs 2

PART 7 - GIFs 3

PART 8 - GIFs 4

PART 9 - Further Notes

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



An Introduction to Graphics for the Web.
Since the inception of the WWW, browsers have used two graphics file formats - GIF (Graphics Interchange Format - originally from CompuServe) and JPEG (from the Joint Photographic Experts Group). Recently versions of the most popular browsers also support the use of the PNG (Portable Network Graphics) file format. However, none of the current browsers display PNG to its full specification and omit such important features such as alpha-channel transparency and the ability to utilise many of the powerful compression filters available. To ensure that the majority of web surfers actually see the images on your web pages, the use of GIF and JPEG images is therefore mandatory. The current tutorial will concentrate on preparing and using GIF and JPEG images. A discussion of the PNG file format will be included in a future article.

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).     

Which image would you use ?
Example 1a. The original image (resampled only) Example 1b. Image manipulated to soften skin tones

Which is the original image ?
Was the photograph taken at sunset or at midday ?
Example 2a. Digitally altered image to simulate the sky at sunset. Example 2b. Original image of a cloudy sky at about midday.

What is the best image format, colour depth or palette to use ?
Example 3a. 24 bit JPEG image with low compression Example 3b. 216 colour Netscape paletted image Example 3c. 256 colour Adaptive palette image with no diffusion Example 3d. 36 colour Optimized palette image with no diffusion

Example 4:    What is the best way to reduce image file size ?
Moderate compression?
24 bit JPEG,
25% compression

6 Kbytes
Convert to paletted

256 colours
adaptive palette

6 Kbytes
High compression

24 bit JPEG,
90% compression

1.5 Kbytes
Colour reduction

6 colours
Optimized palette

1.6 Kbytes