I'll go through the process I used to create the Sig Bar, trying to keep it basic, but adding a few tips and techniques. There are thousands of ways to create a sig bar limited only by your creativity. This is just the process I used on this one.
I used an imported image for the globes and I discuss the use of it at the end of the tutorial. The image...
First I set my document properties for the page size I want to work with. For some odd reason I always use 329x50 for signature images. Not too big or too small.
BTW, I always set the page size for the type of drawing I'm doing, whether it's a sig bar, wallpaper or whatever for the reason that I've found that using blur on an object that extends to the edge of the page will shrink what you're giving blur to. This will have the effect that whatever was behind the blurred object, in another layer, will be exposed.
To counteract this, I make the blurred object extend past the edge of the page. Now when you export the finished image you can select 'Page' as the export area. Anything that falls outside of the page gets left out.
Another reason to use specific page size is that you can export your drawing as a page and it will leave out every other object that might be in that session except what is in the page boundary.
Import your saved image into Inkscape (File --> Import...) and what we'll be doing next is to get rid of the black background. Using the circle tool and holding down the Ctrl key, draw a circle. Drop the Opacity down to about 50% and make the circle match the size and position of one of the globes, again by holding down the Ctrl key and dragging a corner handle so it stays as a perfect circle.
Zoom in to be more precise in size and placement. Once you're satisfied with the size of the circle, tap Ctrl+D twice to make 2 more duplicates. Now position them (left click + hold) on the two other globes.
Select all three circles by left clicking + shift on each, and group the selected objects.
Using the lasso method with the selector tool, select both objects (the imported image and the grouped circles).
Click --> Object --> Clip --> Set.
Move the globes image temporarily out of the way, tap the keyboard number "5" to bring the "page" front and center. Draw a rectangle approximately the size of the page and before leaving the rectangle tool, pull down on the small circle in the upper right corner to round the corners of your rectangle. ** Quick Tip - Use the keyboard numbers 1 through 5 for different levels of zoom. Very convenient, plus zoom key 5 always centers on the Page. **
Adjust to the exact dimensions of width and height.
Use the Align and Distribute dialog and align the rectangle relative to the "Page".
Basically all that's let to do is to choose some colors, apply a gradient, type some text and position all the objects. I used a simple two color vertical gradient as I usually tend toward a minimalist approach.
... and the finished image.
There are a lot of tutorials around on how to apply gradients. What's going to matter most are your design ideas and how you apply them. And for heaven's sake, have fun. There's
(most of what) I create that's flat out crappy but I have a blast trying things.
** About the imported image and copyrights **
First I searched for an appropriate image on this NASA web site from the Shuttle Radar Topography Mission and found this at image #277:http://photojournal.jpl.nasa.gov/targetFamily/Earth?start=270
Then going to this page for a moderately sized image by clicking on the image and then a right click and save as:http://photojournal.jpl.nasa.gov/catalog/PIA03394
The following is a discussion on copyright of images from the SRTM program, of which there are none, even for commercial use.http://pub7.bravenet.com/forum/537683448/fetch/596042/2
Q: Is it illegal to use srtm digital elevation models for hillshadeing on commercial maps, outside the US? Does this DEM have a copyright, or I can use it as base for publishing other commercial maps?Edited to correct zoom quick tip
A: No notification or credit is required for the use of SRTM data. The data available from the U.S. Geological Survey are in the public domain and can be used without restriction. If the data source is acknowledged something simple like "NASA/NGA/USGS" should be adequate.
Consider it a gift from the American people to the world!