Background transparency

[Uli]

Dear all,
I set a transparent background on some of my pictures with Gimp. The pictures are saved as tif-files. Opening them with Gimp or Coral Draw the background is still transparent (1). When I look at them in the Irfan View explorer the background is still transparent, but after opening them the background is coloured with the colour it had before (3).
I don’t think that this is a result of the viewing, because I chosed the settings “show PNG/TIF/TDG/DDS alpha/transparent color”.
I am using Windows 10, Irfan View 4.44 and Gimp 2.8 and enclose the image properties.

Does anyone know how to solve these problems?

Thanks in advance
Uli

[Bhikkhu Pesala]

IrfanView does not display the transparent colour. The transparent area is displayed in the Windows Viewing colour.

If you want to edit 32-bit images, it's better to use another program.

[Uli]

Dear Bhikkhu Pesala,

thank you for your answer.

It is a pity that IrfanView does not display the transparent colour.

I need a program to resize the pictures with batch conversion and in command-line modus. Can you recommend a freeware program for that?

Best
Uli

[Mij]

That Option Show PNG/TIF/TDG/DDS alpha/transparent color often confuses people and it is not obvious how to use it. Irfanview can show TIF images with transparent color but cannot Save them. That probably means that you cannot use it for what you want to do.
Nevertheless, to demonstrate the use of the option I created the attached image using PNG images, which can be both opened and saved with transparent color in Irfanview.


The original image I saved is the large oval band which had a background of blue that I saved as the transparent color. To create the half sized oval that you see overlaying it I checked that "Show PNG/TIF/..." option and Reopened the original image. The oval was now displayed on a gray background which is my Window color that you see on either side of the image. I then resized it and saved the smaller image as another PNG file checking both Save transparent color and Use main window color for transparency in the PNG Save options. By using that second Save option I did not have to tick on the background color manually, so it is what you generally have to use when you are running from a Command line.

For the attached image to show the original blue background I had to open it in Irfanview with the "Show PNG/TIF/..." option Unchecked. I then had to Check that option again before overlaying the half sized oval image using Insert overlay/Watermark image from the edit menu. Otherwise the background of the smaller oval would not be transparent.

It's complicated I know but I wanted to show what is possible.

[Bhikkhu Pesala]

It's complicated I know but I wanted to show what is possible.

Because it is so complicated I never bother to explain what is possible. IrfanView is simply the wrong tool for editing 32-bit images with transparency.

In my opinion, it is simply sending people on a wild goose chase.

I don't know of any freeware programs to recommend for this task. PhotoPlus X8 does have a batch option, and it is only £20 now, but as it is at the end of development it is hard to recommend even at that price.

I don't understand the obsession with using only freeware. IrfanView is not free if you're using it commercially. If anyone is spending a significant amount of time editing large numbers of images then it makes sense to spend a modest amount of cash for software that can do whatever is needed.

[Mij]

I would probably not have replied at all had it not been that in the first post the OP appeared to be reporting a bug. If the OP had checked the Show PNG/TIF/TDG/DDS alpha/transparent color option as implied, then in image (3) the transparent area should show as black, which you can see from the areas either side is the main window colour. I presume that the grey we do see is the original background colour of the image which is now transparent. So did the OP consider Grey to be the transparent colour in the option name and leave the option Unchecked?

I could not find a TIF image with a transparent background (and cannot save one from Irfanview) so cannot test if there is an actual bug. By the time I replied both you and the OP had posted again and were heading off in a different direction. So I described what works with a PNG in the hope that the OP may better explain whether his (or her) TIF works the same way.

[Bhikkhu Pesala]

I could not find a TIF image with a transparent background

Try this image.

sample.tif

[Mij]

Interesting if I open sample.tif in Irfanview I always see the original white background whether Show PNG/TIF/TDG/DDS alpha/transparent color is checked or unchecked, so Uli is correct. Transparency does not work for TIFs if you open directly.

However if I open sample.tif over my image Oval band.png using Insert overlay/Watermark image, transparency does work. The first image below is with the option unchecked when opening both images and the second with the option checked for both.

[rjackal]

Because it is so complicated I never bother to explain what is possible. IrfanView is simply the wrong tool for editing 32-bit images with transparency.

Has the developer explained why this is? Searching the forums, this issue comes up a lot with no satisfactory answer given. PNG is so popular, and transparency support is one of its biggest features.
Of course it's easy for us to complain and create more work for the developer . But on the one hand libPNG and zlib are free and open source, and on the other hand IrFanView has no trouble adding seemingly dubious features like audio and video support, while PNG is not fully supported. It's curious.

I use the batch editing feature of IrfanView because it is so powerful, and I always get burned by the fact that transparent PNGs do not work when batch editing/saving.

[Bhikkhu Pesala]

See this earlier thread.

Open any 32-bit image with transparency and look at the Image Information dialogue.

[rjackal]

Thank you for the pointer to that helpful information.