From 17dd59e72207f8f810141bb9a73c7015c74dca3a Mon Sep 17 00:00:00 2001 From: Johannes 'josch' Schauer Date: Wed, 6 May 2020 08:55:46 +0200 Subject: [PATCH] README.md: clarify PDF transparency (closes: #76) --- README.md | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/README.md b/README.md index 95e6ee8..846f1fa 100644 --- a/README.md +++ b/README.md @@ -77,10 +77,10 @@ Bugs files with other colorspaces, you must explicitly specify it using the `--colorspace` option. - - Input images with alpha channels are not allowed. PDF doesn't support alpha - channels in images and thus, the alpha channel of the input would have to be - discarded. But img2pdf will always be lossless and thus, input images must - not carry transparency information. + - Input images with alpha channels are not allowed. PDF only supports + transparency using binary masks but is unable to store 8-bit transparency + information as part of the image itself. But img2pdf will always be lossless + and thus, input images must not carry transparency information. - img2pdf uses PIL (or Pillow) to obtain image meta data and to convert the input if necessary. To prevent decompression bomb denial of service attacks,