Vectoraster is a graphics utility for creating vector-based raster patterns and halftones based on images or gradients. The raster patterns and point shapes can be changed and varied across the pattern to produce many different styles.
The resulting raster is always shown, updating in real time as you change parameters. The result can then easily be exported as vectors to EPS or PDF files, as images to JPEG, PNG or TIFF, or simply copied and pasted into most graphics software.
You can download and try Vectoraster for free, but with some limitations. To remove these limitations and get the full version you have to pay for the application.