TechNote (Archived)

How do the Trace Bitmap Settings in Macromedia Flash Work?

Issue

The settings in the Trace Bitmap dialog box are touched on briefly in the Macromedia Flash manual, but this TechNote will provide a more thorough explanation of these features.

Solution

The following will provide information on the settings for the Trace Bitmap dialog box:

The four settings in the Trace Bitmap dialog box determine the degree of accuracy in which the Trace Bitmap feature reproduces vector elements from the original imported bitmap. The degree of accuracy ranges from reproducing each pixel with a separate vector object, to outlining areas of pixels of similarly interpreted colors with few vector objects. The higher the degree of accuracy specified by these settings increases the amount of vectors that are generated.

Here are the settings and their definitions:

Color Threshold: The range is from 1 to 500. This setting determines the degree to which one pixel may vary in color from adjoining pixels before Macromedia Flash interprets them as different colors. As you increase the threshold value, you decrease the number of colors.
Minimum Area: The range is from 1 to 1000. This setting determines the size in pixels of each shape generated by the trace. The lower the setting, the smaller the shapes generated.
Curve Fit: This menu has six settings that range from Pixels to Very Smooth. These menu settings determine how closely the edges between the individual vector shapes conform to the bitmap colors. The Very Smooth setting draws longer curves, while the Pixels setting creates many short curves.
Corner Threshold: This menu has three settings; Many Corners, Normal, and Few Corners. These menu settings control the degree a single curve can bend before breaking into two separate curves with corners. Many Corners will yield a smoother line.

Note: Tracing a bitmap using a combination of the highest settings can generate an element larger (in resulting file size) than the original bitmap. It is best to experiment with different settings in order to find the right balance of image quality versus file size.