Upsample/downsample images

Sometimes it is required by a printer that all images in a PDF have at least a certain resolution. This can be difficult, especially if the low-res images are not available in a higher resolution, or the other way around.

pdfToolbox 13 has upgraded the handling of downsampling or upsampling images by adding some new methods to predefined Fixup Properties.

Downsample/compress images

  1. The available downsampling methods are:
    • Average downsampling
    • Subsampling
    • Bicubic downsampling
    • Lanczos downsampling
    • BlackmanSinc downsampling
  2. "To": The target resolution
  3. "For images above": Images above the defined threshold would be excluded from downsampling
  4. Quality: Allows for specifying the quality level in which JPEG objects are saved after the conversion.
    Note: The given value is interpreted as a percentage declaration between 0 and 100. Following you find the possible values and the equivalent setting in Adobe Photoshop:
Adobe photoshop values JPEG quality compression
20 Minimum
40 Low
60 Medium
80 High
100 Maximum

Upsample/compress images

  1. The available upsampling methods are:
    • Average upsampling
    • Bicubic upsampling
    • Lanczos upsampling
    • BlackmanSinc upsampling
  2. "To": The target resolution
  3. "For images below": As it does not make much sense to upsample images with a very bad resolution, images below the defined threshold would be excluded from upsampling
  4. Quality: Allows for specifying the quality level in which JPEG objects are saved after the conversion.
    Note: The given value is interpreted as a percentage declaration between 0 and 100. Following you find the possible values and the equivalent setting in Adobe Photoshop:
Adobe photoshop values
JPEG quality compression
20 Minimum
40 Low
60 Medium
80 High
100 Maximum

More about the methods

When to use which method totally depends on the user. Here are some external links to: