09-16-2021, 05:04 PM
One problem with PDF format is finding a viewer that supports displaying an alpha channel. Nothing I use in linux, I believe Windows Ad*be viewer has settings for this. Then re-opening in either Gimp or PS and ...no transparency No solution I know of for that.
You can check the image properties with command line ImageMagick
This from a single Gimp layer
This from two layers the bottom a white underlay. This I assume for printing where there is no "white" ink. Offset printing can create a white layer before the usual CMYK but this is expensive, you need to ask your printer about this.
Tiff can save to 'pages' and use 'clipping paths' Have a look at Scribus (which makes the best PDF for publishing) maybe you can use something from here; https://wiki.scribus.net/canvas/How_to_I..._text_flow
Again the best ask your printing company.
You can check the image properties with command line ImageMagick
Code:
magick identify -verbose filename.pdfThis from a single Gimp layer
Quote:I also would like to add a "white" channel (for undercoat printing) to the very same file
This from two layers the bottom a white underlay. This I assume for printing where there is no "white" ink. Offset printing can create a white layer before the usual CMYK but this is expensive, you need to ask your printer about this.
Quote:..I would need to do this with TIF files too. TIF is OK with transparency but not channels
Tiff can save to 'pages' and use 'clipping paths' Have a look at Scribus (which makes the best PDF for publishing) maybe you can use something from here; https://wiki.scribus.net/canvas/How_to_I..._text_flow
Again the best ask your printing company.