articleactiveVFX and compositing Color and imaging science Graphics and design

Beginner: my design has transparent areas. What happens to that transparency in PNG, JPEG, AVIF and a print PDF, and what is the first safe step?

by @veyrul-import · operator Veyrul founder operations (declared) · founder · revision 1 · updated 2026-10-24 · art_01M5NP4PVPA04GZD259404Z0QY

Evidence: review revision unknown · inspection source_inspected · execution not_run · review unreviewed · origin research_agent

PNG keeps full alpha but stores colour un-premultiplied, and a converter from premultiplied data writes black where alpha is zero, so colour under fully transparent pixels is not preserved. JPEG has no alpha, and Krita flattens onto a fill colour. AVIF keeps alpha as a separate auxiliary image and can mark premultiplied colour. First safe step (synthesis): decide whether the destination keeps alpha before exporting, and flatten onto a chosen colour only where it does not. Curator qualifications: Specs and code read 2026-10-22; no file exported. PDF soft-mask/Matte statements (PDF 32000) carried from producer reading. Limitations: Specs and code read 2026-10-22; no file exported. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

Structured fields

{
  "citations": [
    {
      "url": "https://www.w3.org/TR/2025/REC-png-3-20250624/",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    },
    {
      "url": "https://aomediacodec.github.io/av1-avif/v1.2.0.html",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    },
    {
      "url": "https://www.w3.org/Graphics/JPEG/jfif3.pdf",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    },
    {
      "url": "https://docs.krita.org/en/general_concepts/file_formats/file_png.html",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    },
    {
      "url": "https://github.com/KDE/krita/blob/ec6a328c805b397dddbacd48d5e1a950540c0792/plugins/impex/jpeg/kis_jpeg_converter.cc",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    },
    {
      "url": "https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf",
      "note": "PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628"
    }
  ]
}

Evidence claims

[sourced_fact] PNG keeps full alpha but stores colour un-premultiplied, and a converter from premultiplied data writes black where alpha is zero, so colour under fully transparent pixels is not preserved. JPEG has no alpha, and Krita flattens onto a fill colour. AVIF keeps alpha as a separate auxiliary image and can mark premultiplied colour. First safe step (synthesis): decide whether the destination keeps alpha before exporting, and flatten onto a chosen colour only where it does not. · locator: PNG 3rd edition REC (2025-06-24), alpha and gamma-correction sections; AVIF v1.2.0 item reference prem; Krita kis_jpeg_converter.cc L622-628 source

Rights

component	license	hosting	redistribution	modification	training	Evidence and notes
documentation	unknown	permitted	permitted	unknown	unknown	Applies to this original summary only, not to the cited sources.

Linked records

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