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I covered the basics of Bitmap Tracing on Page 4 of WebXealot 26. If you need more information please follow this link. I shall try to show some examples here of how the different settings effect the final trace.

For this exploration of Bitmap Tracing settings we will use this black and white bitmap logo for Monty's Chains, a fictitious company invented by your editor for this exploration. As revealed on the previous page, although this image looks like it is only black or white, there are many intermediate shades a gray used to smooth the outline of the text and logo elements.

This example shows how Anti-aliasing works. The S is the S in the bitmap logo enlarged 1000%. Without Anti-aliasing, the text is jagged and stair-stepped.

Anti-aliasing adds subtle intermediate shades of color (in this case shades of gray) which when viewed actual size are not apparent. But the end result is a smoother appearance which oddly enough, makes the object appear sharper and crisper.

When Xara traces the bitmap it has to make a determination of which of these Anti-aliased pixels to count as the object's outline, and which to ignore.

Xara uses a set of algorithms that meet a general criteria for a type of bitmap which it feels will give the best results while at the same time not creating too many points on each object. (Too many points increase the file size and may fail to print on some older PostScript output devices). And while these settings are serviceable, with tweaking, we can do better.

You remember Tad Bridenthal advised us to take notes and more notes when tracing. Following Tad's advice, I have recorded my settings as you can see in these examples.

The Monochrome trace option is found in the Trace types drop down list (under Photographic, the default trace method) and produces a one-color trace result. While the default settings produces a pretty OK result (left), reducing the Noise and Minimum area settings to 0, bumping the Accuracy setting to 100 , and reducing the Smoothing setting to 0 produces a better result, at least where the type is concerned.

I decided to experiment with some of the other trace methods, and for these two examples, used the Grayscale tracing method.

The default Grayscale setting produced very poor results. However with a little tweaking the overall image is much cleaner and more faithful to the original both in terms of the weight of the chain links and the appearance of the text.

The example on the right has a small amount of Smoothing added which reduces some of the jagged quality seen in the far left image. So, for tracing black and white bitmaps, Grayscale seems to produce slightly better results than Monochrome.

Tracing a color photographic image using the default Photographic tracing options produces a relatively acceptable image (right side).

Slivers of red found their way into all the shapes as Xara must have determined red to be the background color.

Although I reduced the bitmap (from the Photographs 1 section in the Clipart Gallery–the images are on the Xara X CD) to 25% its original size, Xara traced the bitmap at the original size and Inserted the image in it's original full size.

Increasing Remove Noise to 100 and Smoothing to 100 should have reduced the red slivers. And while it did a little, it did not reduce them enough to make the image any better. The highlights on the pencils turned out a little bit cleaner however.

Theoretically, adding more passes should produce a more accurate image along with pushing the Accuracy setting all the way to 100.

I'm not sure that it did.

Bottom line, as far as your editor is concerned, best to stick to the default Photographic settings for color images.

Why would you want, or need, to trace a color bitmap image anyway?

Beats me!

About the only two reasons I can think of are for scalability, as vector images can scale up and down without any loss of quality. Of course scaling an image with red slices showing through might not be all that good a thing.

But traced images take on a painterly appearance, kind of like the paintings of artist Wayne Tiebold. And that is not altogether a bad thing. The red slivers become the under painting, which many painters use to build their paintings on top of. So that might be a good reason to trace color bitmaps. A few other possible examples will follow on the next page.