When trapping images, the software calculates the neutral density of the image by determining the average of a sample of image points along the trapped border. Neutral density is one of the parameters that affects a trap decision.
Note: Image border color is measured along the border, while image color (as an object), is an average of the whole image.
You can change how images will trap by enabling or disabling specific parameters.

1. In PDF Trap Editor, select the Detailed view of the Trap Page or Trap Selection dialog box.
2. Click the Images tab.
3. Perform one of the following actions:
   • Select the Trap between images and objects check box to allow traps between images and other objects.
   • Clear the box to prevent trapping between images and other objects.
4. Perform one of the following actions:
   • Select the Trap between images and images check box to allow traps between images and other images.
   • Clear the box to prevent trapping between images and other images.
5. When trapping images, you can specify an image Trap Direction by selecting one of the following from the list:
   • Automatic: Choose the trap direction based on neutral density (default)
   • Center: Creates centerline traps between images and objects
   • Into image: Traps object into image (choke the image)
   • Into object: Traps image into object (spread the image)

   Choosing one of the last three settings will override any automatic assignment of trap direction by the software using the neutral density (relative brightness) of adjacent objects.

6. To help reduce file size, you can specify that any image data in the trap area be resampled to a lower resolution.
   The range is 10 to 1000 dpi.

   When output, the nontrapped area of the image will be high-resolution, and the area inside the trap will be low-resolution.

7. To trap a page containing colorized bitmaps, PDF Trapper must trace the outline of all nonwhite pixels to create vectors to use as traps.
   You can specify how you want a bitmap to be processed by selecting one of the following from the list:
   • Trap All: Traps all colorized bitmaps with vector traps, no matter how complex the bitmaps are. This can take some time, even hours, to complete.
   • Ignore Complex (default): Converts and traps colorized bitmaps except for very complex bitmaps. Any bitmap that is estimated to take more than 30 seconds to trap, or that has a high resolution, is considered a complex bitmap and is not trapped.
   • Ignore All: All bitmaps are considered complex bitmaps and are not trapped.
     
     Note: Copydot images are ignored for trapping.

See Also

Changing the number of traps generated