I have a problem where PDF's look fine on screen, but when printed the transparent parts of PNG images are darker than I think they should be.

I think this is the same problem as this topic.

I have a attached an example html file.
For the test.png use:


On screen everything looks fine. When printed the bottom 3 images all have a darker transparent region (the second image is difficult to tell, but I have digitally printed and confirmed its not white). I'm guessing this is something to do with alpha channel transparency possibly relating to gamma conversion?

I have tried printing with adobe and foxit reader.

Any ideas?

Thanks,
Dan

1. test.html‎ 0.6 kB ‎
   example html

I don't think it's gamma conversion; the alpha channel is being embedded in the PDF as a "soft mask", with zero opacity in all the right places. And as you said, it displays fine on screen. But transparency is often a minefield when it comes to printing and printer drivers.

When you say digitally printed, did you print it to a file and observe the difference? I would like to reproduce the issue here without buying another ink cartridge.

I think this is a color management issue.

I just made a PNG, JPEG, TIFF and inline SVG, all of one color, and put them on the same color background.

When printed the PNG/JPEG/TIFF all go darker, but the SVG and background does not.

When I rasterise the PDF however, they all come out the same one color, like it displays on screen.

It seems like the PDF viewers or printers somehow decide to apply different color management for images in Prince PDF's than is applied to the rest of the document?

Edited 2 Jul 2014 by dancotter

That's tricky. I will see what colorspace properties are available for PDF content. The image is already DeviceRGB, as are SVG and background colors, but perhaps they are being combined in an odd way. If it is affecting JPEG as well then it is not a transparency issue.

Hi Guys, I'm having the same problem. Does Someone have the solution?

In screen looks perfect but only in print when having tons of grey at back of the PNG shows darker transparency

Which version of Prince are you using?

Hi Mike, tried with 11 and 12.

Another thing I noticed is the type of PDF exported is:
U.S web coated (SWOP) v2

According to the people in de graphic area, the ideal would be this format: Coated FOGRA39 (ISO 12647-2:2004) is possible to change this, or this may be the cause? Because the first one is used more for web purposes and not for print?

Are you specifying a PDF/X profile with the --pdf-profile option? You can also use the --pdf-output-intent option to specify a different ICC color profile.

I'm using prince between DocRaptor.
Only PDF/X-4 gives transparency. Other not. I will check about the ICC colors. But the colors are not primordial. My biggest problem is the PNG transparency. I'll upload some examples.

I sending examples of how are generating types of pdf, and the difference with a background in grayscale, and other colors

1. PDFA_1a.pdf‎ 4.1 MB
2. PDFX1a2001.pdf‎ 598.3 kB
3. PDFX_4.pdf‎ 4.6 MB
4. red.pdf‎ 4.2 MB ‎
   With other colors print normal
5. withGrey.pdf‎ 4.2 MB ‎
   This is the problem, grey background