Update README.md

README.md

@@ -3,4 +3,44 @@ Network printing for Sailfish OS
 
 ![SeaPrint icon](icons/172x172/harbour-seaprint.png)
 
-Print PDFs and images over IPP (Internet Printing Protocol). Most, but not all, IPP-capable printers are supported. For printing PDFs, SeaPrint relies on the printer either supporting PDF natively, or the optional dependency `poppler-utils` to convert to Postscript, PWG-raster or URF-raster. Images can be printed on printers accepting JPEG, PNG and GIF as well as PWG-raster or URF-raster.
+Print PDFs and images over IPP (Internet Printing Protocol).
+
+Most, but not all, IPP-capable printers are supported.
+
+A minority of printers support only PCL and/or their own proprietary formats, these are not supported.
+
+## Format support
+
+In order to work with more printers, SeaPrint can use `poppler-utils` (pdftoppm, pdftops, pdftocairo) to convert PDFs.
+
+For PDFs, your printer needs to support one of the following formats:
+ * PDF
+ * Postscript (needs poppler-utils)
+ * PWG-raster (needs poppler-utils)
+ * URF-raster (needs poppler-utils)
+
+For Postscript, your printer needs to support Postscript natively.
+
+For printing "Office" files, like .doc(x) and odt, you need to install
+ `calligraconverter` (from the `calligra` package in Sailfish OS 4.2 onwards).
+ Then the printer support follows that of PDF.
+
+For images, your printer needs to support one of the following formats:
+ * PNG
+ * JPEG
+ * PWG-raster
+ * URF-raster
+ * PDF
+ * Postscript (needs poppler-utils)
+
+For printing JPEG images, transferring the unaltered image has priority and the printer does the scaling.
+Other image formats are lossless and SeaPrint does scale-and-rotate to fit, so JPEG has lowest prio there.
+
+Printers with any of these IPP certifications/sub-standards should likely be supported:
+
+ * IPP Everywhere
+ * AirPrint
+ * Mopria
+ * WiFi Direct
+
+(obviously SeaPrint is unaffiliated and uncertified)