GD Magic: Apply effects on images using only GD

This class can be used to apply effects on images using only the GD image extension.

It takes an handle of a previous loaded or created image with the GD extension and can apply several types of effects using only functions of the GD library.

Currently it can draw a gradient stripe of given colors, replace the color of points with a given color, convert the color of points to gray scale tones, invert the colors of the points, and perform several other effects like blur, edge detect and emboss.