Generate bleed from page content

With pdfToolbox, you are able to create bleed in a number of ways:

  • by mirroring page content as an image at the edges of the page
  • by mirroring page objects at the edges of the page (without rasterisation)
  • by repeating pixels at the edges of the page
  • by stretching the content at the edges of the page
  • in all cases bleed may be generated
    • just for the edges (and not for the corners)
    • for the edges and for the corners

The "Generate bleed on page edges" can be configured very flexibly. The following article explains all the settings you can make in the Fixup.  

How to create bleed by mirroring page content at the edges of the page

The following section contains a tutorial that shows how to generate bleed by means of mirroring the page content at the edges and corners of the page.

Bleed_Demo_file_1.pdf

Open the sample PDF and the "Generate bleed at page edges" dialog

Open the attached PDF "Bleed_Demo_file_1.pdf" (or your own document) and create a new Fixup.

  • Fixup category: Pages
  • Fixup type: Generate bleed at page edges

Configure the "Generate bleed at page edges" Fixup

1. Method

In the "Method" drop down list, you can choose between 4 different methods. In our example the method "Mirror as image (edges and corners)" is used.

The following methods can be used for the bleed generation:

Method Explanation

Mirror as image (edges)

OR

Mirror as image (edges and corners)

 Should be used by default, as it covers a wide range of use cases. Should be used, when images or patterns are close to the Trim Box.

Using this method, the colorspace for the created image needs to be defined. 

Repeat last pixel as image (edges)

OR

Repeat last pixel as image (edges and corners)

 With this method, only the last pixel is used for bleed generation. It can be used, if text objects are close to the Trim Box, to avoid that the text objects are included in the bleed. If images or patterns are close to the Trim Box, this method should not be used.

Using this method, the colorspace for the created image needs to be defined.

Mirror page objects (edges)

OR

Mirror page objects (edges and corners)

 More precise result than the "Mirror as image" method, because the bleed is not generated as an image. With this method all page objects are mirrored individually (vector objects are mirrored as vector objects etc.). However, this means that more document overhead is created.


A colorspace is not defined, the mirrored page content simply keeps its existing colorspace(s).

Stretch border area as image (edges)

OR

Stretch border area as image (edges and corners)


 Good solution when edges should not be visible. For bleed generation also the page content inside the Trim Box is changed, because it is used for stretching. This method will often be used for large format documents, as it is less noticeable at large page sizes.

Using this method, the colorspace for the created image needs to be defined.

2. Repeat only

Here you can define what content  you want to repeat in order to generate bleed. You can use a filter to limit the bleed generation to certain objects or properties.

3. Except spot colors

Specified spot colors are excluded. Here you can set, for example,  that the Cutline is not taken into account for the bleed generation.

4. Resolution

Here you can specify a resolution in ppi for the generated bleed. 300 ppi is the default and should be used for print products.

The Checkbox "Smart resolution for page dimensions > 75 cm" enables auto adjustment of the resolution for PDF files with at least one page dimension greater than 75 cm. Read more about Smart Resolution here.

5. Colorspace

The bleed can be generated in a number of color spaces. In our example, the colorspace setting "CMYK and spot colors" is selected because the orange stripes have the spot color "HKS 10 N"  and we want to keep the spot color in the bleed as well.

The following settings for the "Colorspace" parameter are available:

  • OutputIntent if present or CMYK (CMYK will be used if no OutputIntent is present)
  • CMYK (any spot colors will be converted to CMYK)
  • CMYK, keep spot colors (A DeviceN color space is created so that spot colors are preserved. Should always be used when objects with a spot color are close to the Trim Box)
  • RGB (sRGB IEC61966-2.1) , all colors that are neither sRGB nor plain RGB will be converted to sRGB
  • Grayscale, all non-grayscale colors will be converted to grayscale

The checkbox "Suppress empty color channels (slower)" will only be enabled if "CMYK, keep spot colors" is selected as color space. If this checkbox is checked, the Device N color space of the generated bleed will contain only the colors that appear in the rendered image. Using this option may slow down processing.

6. Checkboxes

The following checkboxes are available:

Tag generated images with ICC-profile: If a document does not contain an output intent, the bleed can be tagged with the default ICC profile used for rendering. 

Set overprint: This checkbox should remain unchecked in most cases. It should only be activated if a cut contour is included in the document. By activating the checkbox, the new bleed will be set to overprint so that the cut contour is not covered.

Create bleed behind current page content: This checkbox should only be activated if bleed already exists in the document and you just want to extend it.

Create on layer: The bleed can be created on a new layer.

7. Parameters

Click on the edit button (pen icon) to configure the desired bleed geometry in a separate "Generate bleed at page edges parameters" dialog:

  1. Create bleed at: Here you can select which page geometry box shall be used as source for the edges used for bleed generation; usually the TrimBox is used here (if available), or the CropBox. It is also possible to define a "CustomBox" in which case the four parameters just below this option are enabled, and suitable values can be entered.
  2. Use width of BleedBox for generated bleed: If the document already contains a BleedBox that only needs to be filled with content, this checkbox can be activated. Thus, not the value specified under "Bleed width" is used but the current width of the BleedBox (the specified offset is taken into account).
  3. Set BleedBox: Here you can specify whether the BleedBox should be set again after bleed generation. If the BleedBox is already correctly defined in the document, the setting "ignore" can be used. If there is no bleed in the document yet, "Always (override existing)" should be set, or if there is no BleedBox at all, select "If missing".
  4. Bleed width: The "amount" of bleed to generate.  
  5. Derive offset from page: Since pdfToolbox 15 it is possible to automatically determine if an offset is needed. If the existing page content does not go straight to the TrimBox (ends close to the TrimBox), pdfToolbox will detect this and go inside the TrimBox to the edge where the page content actually ends and generate the bleed at that position. This method avoids thin white lines between the generated bleed and the page content. And it also works if there is already an existing bleed that is not big enough. pdfToolbox will detect the existing bleed and complete the missing bleed by generating the new bleed after the existing one.
  6. Offset to box: Up to pdftoolbox 15 it is possible to set a fixed offset that will always be used for bleed generation to adjust pages where the page content ends just before the TrimBox. A negative offset value moves the source area for the bleed to the center of the page, a positive value moves the area to the outside of the page. A negative offset is useful when the page content ends just before the page edges, leaving a thin visible white line after the bleed is added. A small offset (such as -0.2 mm) can be specified for this use case.

8. Apply to

Here you can use a filter to specify to which pages the bleed generation is applied.

Review the processed PDF file in pdfToolbox

5 mm bleed is added on all sides of the PDF file by mirroring the content as an image.

Different set of parameters for "Stretch border area as image"

In case the "Stretch border area as image" mode is used for generating bleed from page content, two additional parameters are shown that need to be configured:

  1. Source width: Width of the area within the TrimBox to be used for stretching. The source area as well as the bleed are displayed in the form of an image (depending on the "Bleed width") .
  2. Stretch factor: Factor for the exponential function to calculate the increasing stretch effect. The same stretch factor is used for all four sides. The content in the source area is "stretched" to varying degrees: the closer to the edge of the page, the lower the degree of stretching. The slope of the underlying "stretch curve" is controlled by the stretch factor.