“Blender” calculates the number of steps necessary to obtain a smooth transition from one color to another when using the blend tool in PostScript illustrating programs like Adobe Illustrator or Aldus FreeHand. The result is based on the equation given in issue 6 of Adobe’s publication “Colophon,” plus more recent Adobe guidelines suggesting screen and resolution settings that allow the PostScript maximum of 256 shades. Please note that these calculations are only guidelines—sometimes they’ll work beautifully, and sometimes they’ll only minimize your disappointment.
• Fill in the blanks to define the process colors you’re blending between. Blender bases its calculation on the ink color with the largest change so you can use, for example, the cyan field only (the other 3 inks set to 0%) to calculate blend steps for black or PMS inks.
• Fill in the Screen Frequency (halftone lines per inch) and Printer Resolution (dots per inch). Some common values can be selected from the pull-down menu.
• Click the OK button or press the Enter or Return key, and Blender will calculate the number of blends. The numbers given are:
- The total number of shades possible (in a 0% to 100% blend) with the given screen and resolution settings.
- The number of steps in the requested blend.
- The number of intermediate steps between the starting and ending values (the number entered in Adobe Illustrator's Blend dialog box). The intermediate steps will also be placed onto the clipboard, ready to be pasted into your drawing program.
Multifinder Note: this version of the program now copies to the clipboard under Multifinder.
• Leave the “Suppress Warnings” check box unchecked to allow the Blender DA to alert you to an illegal or questionable value in an edit box, such as all four process colors run near 100%.
• Pressing the “More…” button (or Command-M) will bring up another dialog box providing more information on the blend you’ve defined. If no blend is defined, Blender will beep at you. The dialog box will inform you of the highest possible screen frequency that will still allow the full 256 shades at the given resolution. For the benefit of illustrators who have the freedom to lower the screen frequency for a smoother blend, the dialog box will also give you the maximum line screen to use at the desirable blend length of 1 point per step, and the maximum recommended blend length of 2 points per step, based on the printer resolution you’ve selected. Press the “Measure my blend…” button and the dialog box will disappear, leaving you with a cross-shaped cursor with which you can drag a line across your blend area (be sure your drawing program is in actual-size view). The dialog box will return and you'll be informed of the length of your blend and the highest recommended line frequency for a smooth blend.
• There are some instances where you may be able to cheat a little on the number of blends. If the color with the largest percent change was yellow, you may get away with fewer steps, since a little subtle banding in yellow would be less noticeable than in darker colors. If the number of steps is greater than the number of points between the starting and ending paths, you may be able to cut back. In general, more than 2 points distance between paths could result in banding, while less than 1/2 point is probably a waste of memory and processor time. Using combinations of 2 or 3 colors can help reduce visible banding.
• On an extended keyboard, pressing the Home key selects the From»Cyan edit box, and pressing the End key selects the Screen Frequency edit box.
• To change the default values in an edit box, simply change the values in the DITL resource with ResEdit or other resource editor.
• Please Note: This software suits my purpose as an illustrator, and works reliably on my equipment. I cannot guarantee that it will work flawlessly for you—SAVE YOUR WORK before opening this or any other DA. Question any bogus-looking results! The magic formula this program is based on is (dots per inch/lines per inch) squared x percent change in color = approximate available steps. The power-user formula in the “More…” button is: highest recommended screen frequency = printer resolution x the square root of ((change in color x .03)/length of blend in inches) as described in the February 1991 issue of MacUser magazine.
Special thanks to Andy Rogers of Rogers Projects and Wendy Krivoshein of Web Tech for their generous assistance. Thanks also to Michael J. Conrad for for his “DA Skeleton.” If you find Blender useful, please let me know. If you're thrilled with it, I’d really appreciate a donation to cover the cost of my books ($1 to $5 is great!). Your comments, suggestions, and—especially—bug reports are always welcome.
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