For the function to do what it promises, the following requirements must be met:

• the PDF file contains color, grayscale and/or monochrome images.
• the PDF file contains images with a resolution higher than the resolution entered in the option For Images above [3].

Figure 1: The dialog Downsample and/or Compress Images

You can use the following options in the Fixup:

• Templates [1] – Settings selected in the dialog can be saved as a template and thus applied to other Articles/Print Items.

Color/Grayscale Images

• Downsample [2] – select the method for downsampling color and grayscale images here. The following options are available:
  • Bicubic – when carrying out bicubic downsampling, the color value for the newly created pixel is calculated by averaging the color values. During the calculation, attention is paid to the surrounding pixels, and the average value is weighted accordingly.
  • No Downsampling – the resolution is not changed, the number of pixels remains the same.
  • Variable Content [10] –select the desired placeholder - database field or user-defined field - from which the value for the recalculation method is to be taken. The following values must be found in the selected field so that the downsampling can be carried:
    • BicDownsampling
    • Off
• For Images above [3] –  enter the minimum resolution of the images in dpi that that the downsampling should affect. For the Variable Content [4], select the desired placeholder - database field or user-defined field - from which the value for the minimum resolution for the images that should be reduced is retrieved.
• Recalculate to [11] – enter the desired target resolution in dpi that the image should have after downsampling. For the Variable Content [12], select the desired placeholder - database field or user-defined field - from which the value for the target resolution is retrieved.
• Compression [5] – select the desired compression type from the selection menu. The following compression types are available:
  • Retain existing – the existing compression of the images is retained.
  • Lossy (JPEG) – the images are compressed with lossy compression using the JPEG algorithm.
  • Verlustfrei (ZIP) – the images are compressed without loss using the ZIP algorithm.
  • Variabler Inhalt [13] – select the desired placeholder - database field or user-defined field - from which the value for the compression algorithm is retrieved. The following values must be found in the selected field for images that should be compressed:
    • RetainExisting
    • JPEG
    • ZIP

Figure 2: Left: Values in the selected field for the Downsampling option; Right: Values in the selected field for the Compress option

Monochromatic Images

• Downsampling [6] – select the method for downsampling monochromatic images here. The following options are available:
  • Bicubic – with bicubic downsampling, the color value for the pixel to be created is calculated by averaging the color values. During the calculation, attention is paid to the surrounding pixels and the average value is weighted accordingly. If the weighted value is above 50 %, a black pixel is created. A white pixel is generated for all values below 50 %.
  • Downsampling – during downsampling or Subsampling, the middle pixel is combined into one large pixel, depending on the matrix.
  • No Downsampling – the resolution is not changed, the number of pixels remains the same.
  • Variable Content [14] – select the desired placeholder - database field or user-defined field - from which the method for downsampling is to be taken. The following values must be found in the selected field for the downsampling to be generated:
    • BicDownsampling
    • Off
    • Subsampling
• For Images above [7] – enter the minimum resolution of the images in dpi that are to be affected by the downsampling. For the Variable Content [8], select the desired placeholder - database field or user-defined field - from which the value for the minimum resolution of the images that should be reduced is retrieved.
• Recalculate to [15] – enter the desired target resolution in dpi that the image should have after downsampling. For the Variable Content [16], select the desired placeholder - database field or user-defined field - from which the value for the target resolution should be retrieved.
• Compression [9] – select the desired compression type from the selection menu. The following compression types are available:
  • Retain existing – the existing compression of the images is retained.
  • CCITT Group 4 – the images are compressed losslessly using the CCITT Group 4 algorithm.
  • JBIG – images are compressed with lossy compression using the JBIG algorithm.
  • Run Length Encoding – the images are compressed without loss using the RLE algorithm.
  • Variable Content [17] – select the desired placeholder - database field or user-defined field - from which the value for the compression algorithm that should be used is retrieved. The following values must be found in the selected field for the compression to be generated:

Figure 3:  Left: Values in the selected field for the Downsampling option; Right: Values in the selected field for the Compression option

To experiment with this function, refer to the sample file "Sample_Downsampling.pdf". The image has a size of 364,07 x 242,74 mm and a resolution of 300 dpi.

After applying the Fixup, the file "Sample_Downsampling_End.pdf" is created. The resolution has been reduced to 100 dpi.

Figure 4: Left: Initial file with an image resolution of 300 dpi; Right: Edited file with an image resolution of 100 dpi

Article update: Workflow 1.17.0 – 03/2024