The WebXealot  Page 6

Xara X. Create Bitmap Copy (Continued)

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The second tabbed section in the Bitmap Options dialog is Bitmap Size.

Many of these options are grayed out. When exporting a bitmap, instead of creating a Bitmap Copy, these options are enabled.

Width and Height are the actual width and height of the selection in pixels at 96 dpi (Windows screen resolution). Changing one of these sizes, changes the other size proportionately.

DPI (Dots Per Inch–actually should be Pixels Per Inch) lists resolutions from 50 to 300. An image saved at 96 dpi will display in Windows browsers at the same size the image displays in Xara at 100% Zoom Factor. 75 dpi is more or less Macintosh screen resolution (I believe it's 72 dpi) and will display about 1:1 in Macintosh browsers. 250 and 300 dpi are better suited to printed output, 300 dpi translating to about 150 lpi (Lines Per Inch–used by commercial printers).

NOTE: Using a higher resolution will not add more detail to the image, it just makes the image larger when viewed in a browser. For example, an image saved at 150 dpi will display twice the size as the same image saved at 75 dpi. This is why it's best to save the image at 96 dpi if you want the image to appear same size or 1:1.

Anti-aliasing has two settings: Maintain Screen Anti-aliasing and Minimize Visible Anti-aliasing (checked by default). The difference between the two options is very subtle. Xara recommends using the default setting unless you specifically have designed your image to anti-alias exactly as it appears on the screen.

As always, the most important button in any Xara dialog is Help. Pressing Help in most dialogs produces a context-sensitive menu explaining options offered in that dialog. Preview will refresh the two preview windows in the Bitmap Options dialog if it does not do so automatically. And Create gives Xara to go-ahead to create the image.

Limiting the Number of Colors

When creating a bitmap image with 256 colors or less, Xara generally tries to create the best image possible using what it considers to be the perfect number of colors. As a rule, the result is hard to beat in terms of image quality and small file size. But there are times, when you may want to modify the number of colors.

This image was created using the TrueColor palette option and is only 13K in file size.

The image has degraded slightly because after I created the bitmap copy, I exported it as a JPEG. The original image is smooth and crisp.

Here are four more images saved as PNG bitmap images with 256 colors and less.

Oddly, the images with 64 and 32 colors show less banding than the image with 256 colors. The file size for the first three images is 46K compared to 13K for the TrueColor JPEG image.

The last image, saved with 16 dithered colors looks almost as good as the other images and is a modest 23K. Still, this is almost twice the size of the TrueColor JPEG image.

My suggestion; when in doubt, leave it to Xara.

There is a lot to cover in the bitmap department, and I think I'll continue this chapter next month. We still need to look at the different file formats, TIFF, Windows BMP, Targa TGA, and others. And we will cover all the other bitmap export features found in the Bitmap Export dialog. We'll also look more at PNG (PING) format and how it figures into the future of Web graphics.

We'll also look at creating transparent backgrounds for GIF images and ways to get the cleanest and sharpest image.

In the meantime, if you have any questions, comments, TIPs or Tricks, or have heard of a good joke, use the form on the next page and drop me a line.