flatten-transparency

name	flatten-transparency
description	Flatten transparency in a PDF — eliminates banding, color shifts, and weird overprint artifacts on older or cheaper digital printers. Triggers on phrases like "flatten transparency", "fix banding on print", "flatten layers in PDF".

Flatten Transparency

Convert transparent overlays, alpha blends, and soft masks into solid raster/vector output. Many digital printers (especially older RIPs or budget office units) mishandle live transparency, causing banding or color shifts.

Inputs

• Input PDF path (required).
• Quality (optional) — print (default, 300 DPI raster regions), screen (150 DPI, smaller files), prepress (highest fidelity).
• Output path (optional) — defaults to <input>-flat.pdf.

Tooling

Ghostscript with pdfwrite and -dCompatibilityLevel=1.3 flattens automatically because PDF 1.3 has no live transparency model.

Recipe

gs -o output.pdf \
   -sDEVICE=pdfwrite \
   -dCompatibilityLevel=1.3 \
   -dPDFSETTINGS=/printer \
   -dEmbedAllFonts=true \
   -dSubsetFonts=true \
   -dNOPAUSE -dBATCH \
   input.pdf

Compatibility=1.3 forces flattening. /printer tunes raster quality for print.

Diagnosis (when to use)

Symptoms that suggest transparency is the culprit:

• Soft drop-shadows print as banded gradients.
• Logos with alpha look milky or washed out.
• Colors near transparent overlays shift.

Probe for transparency:

mutool show input.pdf grep -i "/SMask\|/CA\|/ca\b\|/BM"

Hits → live transparency present.

Caveats

• Flattening rasterizes affected regions — file size may grow.
• Text inside flattened regions may become a raster image and lose searchability/selectability. Keep the original.

Output

Flattened PDF. Original preserved — flattening is destructive in the sense that liveness is lost.