Using PhotoMasque in PhotoFiltre
It is important to note that currently only GIF and PNG formats preserve transparency.
The number of colors is small (256) with a method of diffusion.
Creation of personalized masks
Your masks should be made in standard 256 grey colors. It is preferable to use a format supporting the color mode indexes (GIF, PNG, BMP, TIFF) in order to conserve the original quality of the mask without loss of information, particularly if the latter contains degraded content. But, it is possible to use the JPEG format with a low compression ratio.
Tricks and easy ways
In Color mode, apply several layers of the same mask with a different color (blue sky, then white with the Aquarelle mask for example). The combination of several masks gives sometimes an interesting result. Test the mask “Dilution” then the mask “Watercolor” with a white color.