How to Create GIF's from PCB Data

There are several approaches to generating a GIF file and the exact approach depends on your PCB application’s output. Likely sources for an Allegro Board Designer are:

    Screen Dump

    HPGL or HPGL/2 File

    Postscript Print File

    Gerber Data

Screen Dump

There are many ways to get a screen dump depending on your operating system. Solaris 2.5 provides a set of very nice built-in tools - the snapshot tool enables you to capture the entire screen, any window or even any region. It works together with the Image tool that enables you to save the snapshot in a variety of formats such as GIF, EPSI and TIF.
If you don’t have such a tool you can use a public domain program called xv or use the xwd (x windows dump) command.

Are Screen Dumps Useful?

Yes - if you need to show only a very small area.

No - if you need to show details in a complex schematic or layout there are not enough pixels on the screen. Let's use a back-of-the-envelope calculation to see what we can reasonably get from a screen dump.

    A typical workstation screen is 1000-1200 pixels across - if you are trying to show something in a 3 x 3 area then you should be OK. If you are trying to capture a PC board that is 8" x 10" your resolution is down to about 100 dpi - a 10 mil trace will be only 1 pixel wide; an 8 mil trace may disapear altogether.

Examples of Screen Dumps

To illustrate our back-of-the-envelope calculation I used Artwork's XGBRVU program to display a very complex, large signal layer of a computer mother board. I captured two views - one of the entire 15 x 19 inch board and a second of the same board but zoomed in to a 3 x 3 inch area.

Below - scnshot1.gif 664x900 256 color
This image was captured from a Sun Sparc Screen. The vertical resolution limited the total size of the image. You really cannot separate out detail - pads and traces are merged due to the low effective resolution.



Below - scnshot2.gif 664x900 256 color. Now I zoomed in on a small 3 x 4 inch area of the board and captured the screen again. This time you can see what is going on in this circuit. Even so, some pads and some traces still run together. Most of the round pads are 0.030 inches in diameter and the circuit traces are 0.008 wide.

Conclusion

A screen shot is a quick-and-dirty way to get your board on the WEB but -- if your user needs to see detail in the board you are limited by your screen's resolution vs the 100 to 150 dpi needed to see 10 mil features - limiting you to about a 3 x 3 inch area. If you want your user to see the entire board at 100 dpi or better a screen shot is not useful. We'll need to up the ante.

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