Inside Macintosh: QuickDraw GX Objects /

Chapter 7 - View-Related Objects / View-Related Objects Reference

Constants and Data Types

The Halftone Structure

Halftones are described by the gxHalftone structure:

struct gxHalftone{
   Fixed          angle;
   Fixed          frequency;  
   gxDotType      method;     
   gxTintType     tinting;    
   gxColor        dotColor;   
   gxColor        backgroundColor;
   gxColorSpace   tintSpace;  
};

Field Description

angle

The orientation of the rows of dots in the halftone pattern. It is a fixed-point number between 0.0 and 360.0 that describes an angle, in degrees, clockwise from horizontal.

frequency

The size of the cells, in terms of numbers of dots per inch. It can be any positive value.

method

The halftone pattern itself and how it is filled: the shapes of the dots, the pattern of their arrangement, and the way in which a dot fills its cell as it enlarges. The supported methods are defined in the gxDotTypes enumeration, described next.

tinting

The type of calculation by which the input color is to be approximated by a ratio of dot color and background color. Tint types are defined in the gxTintTypes enumeration, described
on page 7-67.

dotColor

The color of the dots used to form the halftone.

backgroundColor

The color of the background used to form the halftone.

tintSpace

The color space the input color is converted to before the halftone calculations are made.

The halftone structure is described further in the section "Halftone" beginning on page 7-13.