Watermark: Apply watermark text to an image

This class can be used to apply an watermark text to an image.

It reads a true color image from a file, draws a watermark and saves the processed image.

The watermark text can be rendered with a configurable true type font, font size and font width scale factor.

The class can load and save images in the formats: GIF, PNG and JPEG.

The resulting image can be saved to a file or generated as part of the current script.

When saving to a file, the class may check whether the output file to avoid overwriting it.