Created attachment 189086 [details] Test document See the attached document, exporting in master results in PDF with emojis as rectangles with hallow circles. This works fine in 7.6. This is reproduced on both Linux with Noto Color Emoji font and macOS with Apple Color Emoji since both are bitmap color fonts.
Created attachment 189087 [details] Broken PDF exported from Linux
Bibisected to: commit 81994cb2b8b32453a92bcb011830fcb884f22ff3 Date: Fri Apr 16 20:33:10 2021 +0200 Convert internal vcl bitmap formats transparency->alpha (II)
The code that writes bitmap color glyphs to PDF is in https://opengrok.libreoffice.org/xref/core/vcl/source/gdi/pdfwriter_impl.cxx?r=c9da81db#2704, in case it helps debugging this.
Khaled Hosny committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/3e20c3e73cbd10e8323f0997e3a6536abd11e2bd tdf#156853: Fix PDF export of bitmap color fonts It will be available in 24.2.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Patrick Luby committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/8dc8413b4f8037b9c89f08a5b0b939bb61052585 Revert "tdf#156853: Fix PDF export of bitmap color fonts" It will be available in 24.2.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
I can reproduce this as well. Unfortunately, the initial fix caused the same bug to now occur with all transparent images and shapes. So I will see if I can find what is unique about emoji bitmaps.
Patrick Luby committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/7d745697eec8dc5702eb0ebaa8c4b5122c31edab tdf#156853: Fix PDF export of bitmap color fonts It will be available in 24.2.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
I committed a fix and it should be in tomorrow's (24 August 2023) nightly master build.