Creating texture with varying alpha values for drawing anti-aliased lines in OpenGL-ES

I am working on drawing anti-aliased lines in OpenGL-ES on iPhone. I am using an approach outlined in iPhone 3D Programming, called "Rendering Anti-Aliased Lines with Textures". The basis idea is to iterate t开发者_如何学运维hrough the line creating a bounding rectangle for each line segment (pair of vertices). This bounding rectangle can be represented by 6 triangles - and these can be filled with a texture. A texture (dot.png) comes with sample code, but I would like to experiment with other textures to see if I can get a more 3 dimensional affect.

So, I am wondering if there is a tool that would help me create these texture images. I have tried using Photoshop - but my skills there are rudimentary. I have seen "GIMP" mentioned, but I have no experience with it. I am guessing/hoping that there is some app out there that is designed for this purpose. Any pointers would be most welcome.

Thanks

If you mean, to create some blurry circles you can try to generate some using imagemagick. Some examples are here for blurring www.imagemagick.org/Usage/blur/ and here for radial gradients: http://www.imagemagick.org/Usage/canvas/#radial-gradient and www.imagemagick.org/script/fx.php