ImageLowRes callback

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

A procedure by this name is  called if an image at too low a resolution is included in the incoming data stream. Two threshold resolutions may be set: one for linework (1 bit per channel) images, and one for contone. These are named ImageLowLW and ImageLowCT respectively. They can be real numbers or integers, and should be 0.0 or greater, or -1 if that specific option should not cause a callback to the ImageLowRes procedure. Both thresholds should be defined in dots per inch.

The procedure is called with six items on the operand stack the image resolution in dots per inch (if the X and Y image resolutions are not equal then it is the lower of the two), the bit depth of the image (1 for linework, greater for contone), and the bounding box of the image, as described for ImageRGB, in ImageRGB callback.

This callback is not invoked if an image is encountered within a Level 2 pattern fill or a Type 3 font.

For example:

  <<
  /ImageLowRes {
    (Image at too low res!)=
    5 -1 0 { index == } for
    gsave
    initgraphics
    0 1 1 0 setcmykcolor 3 setlinewidth
    2 index sub exch 3 index sub exch
    rectstroke
    grestore
    (____________)=
    pop pop % the resolution & bit depth
  } bind
  /ImageLowCT 150
  /ImageLowLW 600
  >> 1183615869 internaldict begin setmischooks end