On Fri, 02 Feb 2007 18:27:50 +0100, Enrico Galletti wrote:

Hi everyone,
is there any tool in GIMP to convert a grey-scale image into a black&white (1 bit bitmap) points cloud image, i.e. an image where the grey scale is given by density of dark points ?

This can be done with a simple conversion to black and white with dithering enabled:
- select Image->Mode->Indexed
- for the colormap, choose black and white (1-bit) - for dithering, select Floyd-Steinberg dithering - click "Convert" and you will get your black and white dots

If the resolution of your image is not sufficient to get nice clouds, the you can scale up the image before converting it to black and white. So you would go to Image->Scale Image and double or triple the width and height before going to Image->Mode->Indexed.

You may also want to play with the overall brightness or contrast of the image before converting it to black and white. You can play with Colors->Curves or Colors->Levels.

Another option is to use the Newsprint plug-in. You can find it in Filters->Distorts->Newsprint, although I doubt that this is exactly what you are looking for.

-Raphaël