Halftone

This transformation lets you render an image using a halftone screen.

Halftoning is a technique for representing a continuous tone image using only two colors -- black and white. These black and white dots are clustered in patterns to simulate the different gray levels in the input image. There are many different halftoning techniques, a number of which are supported by Picture Window. In addition, the halftone transformation can use a custom screen that you supply.

Amount

The amount control lets you control how much of the halftone transformation is applied to the input image. You can apply a percentage of the transformation to the entire image, or you can specify an amount mask to restrict the effects of the transformation to only part of the input image.

Method

This control lets you select the halftoning method from a number of options. The best way to understand the different halftoning patterns is to experiment with this setting. In general, the halftoning patterns with the smallest sizes (e.g. 6x6) are best at representing finer details at the expense of being able to represent fewer different gray levels.

If you select Custom, then you can specify any grayscale image as the halftone screen using the Screen control (see below). To generate the output image, the input image is compared to the halftone screen image, a pixel at a time and if the input image pixel is darker than the screen pixel, the corresponding output pixel is set to black; otherwise it is set to white.

Halftone Screen

The halftone screen image control lets you select a black and white image for use as a custom halftone screen. This setting is ignored unless the Method control (see above) is set to Custom.

For best results, screen images should have roughly equal numbers of pixels of each possible gray level and should have a fairly fine texture. A nearly infinite variety of such screens can be generated using the Texture transformation followed by the Equalize Transformation . The halftone screen image is tiled as necessary to cover the input image and therefore can be any size.

Note: Because of their repeating bit patterns, halftones previewed at a zoom factor other than 1:1 (or higher) often look very strange and this should normally be avoided.

Brightness Curve

The brightness curve lets you tailor the tonality curve of the image for best halftone results. When adjusting the curve pay special attention to shadow and highlight areas to make sure that they show the greatest amount of detail in the halftone.

Add Noise

This control lets you add noise (randomness) to your image to reduce any any patterning or artifacts introduced by the interaction of the mask with details in your image.

Tips

It may be helpful to resize the input image to have more pixels before halftoning.