Browse Prior Art Database

Adobe Illustrator ™ - Macintosh ®: Creating Smooth Blends in Adobe Illustrator

IP.com Disclosure Number: IPCOM000128771D
Original Publication Date: 1994-Apr-22
Included in the Prior Art Database: 2005-Sep-19
Document File: 4 page(s) / 83K

Publishing Venue

Software Patent Institute

Related People

Adobe Systems Inc.: AUTHOR [+3]

Abstract

Tech Note #4003 (4/22/94) This technical note discusses how to create smooth blends (gradient fills) with the Adobe Illustrator program, and how to avoid breaks in color (shade-stepping or banding) in printed blends. To create the smoothest possible blend, you need to consider several factors: The total number of gray levels your printer or output device can produce. This number is determined by the resolution and line screen combination of the printer or imagesetter. The percentage of change in color from the beginning to the end of your blend. Less than a 50-percent change can cause breaks, or banding, in the shades of color. The length of the blend. The length you can use varies with the colors in your blend, but as a general rule, the blend length shouldn t exceed 7.5 inches. The colors you use. Blends between very dark colors and white seem to generate the most banding problems. If possible, use lighter colors, or make dark blends short; avoid very dark colors in lengthy blends.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 32% of the total text.

Page 1 of 4

THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

Copyright ©; 1994 Adobe Systems, Inc. All Rights Reserved. Reproduced with permission. Adobe makes no warranty as to the accuracy or completeness of this material and hereby disclaims any responsibliity therefor.

Adobe Illustrator TM - Macintosh ®: Creating Smooth Blends in Adobe Illustrator

Tech Note #4003 (4/22/94)

This technical note discusses how to create smooth blends (gradient fills) with the Adobe Illustrator program, and how to avoid breaks in color (shade-stepping or banding) in printed blends.

To create the smoothest possible blend, you need to consider several factors:

* The total number of gray levels your printer or output device can produce. This number is determined by the resolution and line screen combination of the printer or imagesetter.
* The percentage of change in color from the beginning to the end of your blend. Less than a 50-percent change can cause breaks, or banding, in the shades of color.

The length of the blend. The length you can use varies with the colors in your blend, but as a general rule, the blend length shouldn t exceed 7.5 inches.

* The colors you use. Blends between very dark colors and white seem to generate the most banding problems. If possible, use lighter colors, or make dark blends short; avoid very dark colors in lengthy blends.

DETERMINING THE BEST RESOLUTION/LINE SCREEN COMBINATION

With most printers, increasing the screen frequency decreases the number of gray levels avail- able to the printer. If the number of gray levels is less than the number required for your blend, the result is a posterized gradation.

Before you create your artwork, determine the number of shades of gray your printer or image- setter can produce. You need to know both the resolution of the printer, expressed as dots per inch (dpi), and its line screen frequency, expressed as lines per inch (lpi), to determine the maximum number of shades of gray your printer can produce.

Levels of gray = [ (Resolution (dpi)/line screen (lpi)) ] 2 up to a maximum value of 256 Examples Low-resolution printer (such as Apple ® LaserWriter ® IINTX or Hewlett-Packard ®

Laserjet ® with a PostScript cartridge): (300 dpi/53 lpi)2 = 32 levels of gray High-resolution imagesetter: (2540 dpi/150 lpi)2 = 256 levels of gray (The calculated value gives 286, but the maximum number of grays is 256 for any device.)

Medium-resolution imagesetter: (1270 dpi/100 lpi)2 = 161 levels of gray

Adobe Page 1 Apr 22, 1994

Page 2 of 4

Adobe Illustrator TM - Macintosh ®: Creating Smooth Blends in Adobe Illustrator

CALCULATING THE OPTIMAL NUMBER OF BLEND STEPS

When blending between two colors, the maximum number of usable blend steps (shades of gray) is based on the limits of your printer or imagesetter and the percentage change in the grayscale value of the blend.

Adobe Illustrator assumes that your imagesetter will produce 256 levels of gray. The percentage change in color is derived by sub...