Tweak to get the perfect trace
Table of Contents
Modifying the Raster Adjustments
The Adjustments settings found on the left side of the Tracing Options dialog apply to the raster conditioning that occurs before the image is traced.
- Mode. Live Trace converts a bitmap image to either 1-bit black and white, 8-bit grayscale, or 8-bit color, which you can choose from the Mode pop-up menu.
- Threshold. The Threshold setting determines the boundaries between pixels when using the Black and White trace setting. For example, in a gray bitmap, a high threshold setting results in more gray pixels becoming black vector objects, and thus a heavier appearance. In that same image, a low Threshold setting results in more gray pixel ignored, making for more white-colored objects and an overall lighter or more delicate appearance (Figure 2). Too low of a Threshold setting may also result in a loss of image detail. The Threshold setting is also available in the Control palette when a Black and White Live Trace object is selected.
Figure 2: Making adjustments to the Threshold setting can have a large impact on the overall appearance of the traced result. Here are examples of an image with a variety of different Threshold settings.
- Palette. By default, Illustrator uses the selective color reduction method to choose the best colors to fit the image (based on the Max Colors value). However, you can choose specific colors that Illustrator should use when tracing your image. To do so, you must first load a custom swatch library (refer to Chapter 1 for instruction on how to define a custom swatch library). When a custom swatch library is opened in your document, the Palette pop-up menu displays all of the available palettes (Figure 3). Live Trace then only uses the colors that appear within the custom swatch library that you choose.
Figure 3: Loading several different custom libraries allows you to quickly experiment with a variety of different color schemes.
- Max Colors. The Max Colors setting determines the maximum number of colors that can be used in the final traced result. This setting is not available for the Black and White Mode setting. Live Trace uses the selective color reduction method to reduce the number of colors in the raster image to match this setting during the conditioning process. The Threshold setting is also available in the Control palette when a Grayscale or Color Live Trace object is selected.
- Blur. The Blur setting applies a Gaussian Blur to the image, which helps remove noise from the raster image. This reduces the number of anchor points in the tracing result, especially when you are tracing photographic images.
Tip: Check the Output to Swatches option to have Illustrator add each color that is used during the tracing process as a global process color in your Swatches palette.
- Resample. The Resample setting lets you change the resolution of the bitmap image to help obtain a better traced result. Resampling a high-resolution image to a lower resolution greatly enhances the speed performance of Live Trace.
