Here's a version of SteveH's equation that I built in Photoshop Elements. (If you don't have that, and don't want to buy it, I recommend that you take a look at GIMP, which is free and very capable. The tools and menu options in the instruction below are probably a bit different in GIMP.)
To create the image, do the following:
- Open a new, blank document in your image program. Choose your image size appropriately, both in image size and resolution. (The base image here is actually too large, as you'll see if you click on it. I should have chosen a smaller upload size.)
- Open a word-processor document. (I used OpenOffice Writer, but Word can work also.)
- For each special character, use the Insert Special Character menu option to find and insert the special character in the word processor. Note: In this equation the apposite special characters were the capital sigma and the not-equals symbol.
- Using the text tool, enter each of the elements of the equation in a separate layer. (For this image, I used five layers: Sigma, main equation, subscript, lower limit, upper limit.) When necessary, copy the special characters and paste them into the image editor. It is not important at this point to place the image elements precisely, we'll move them in the next step, but it is much easier if you choose your sizes appropriately.
- Using the Move Tool, move each element to the place you want it to be in the final image.
- Crop the image to remove most white space around the live part of the image.