PNG files open as negatives

[tomczak]

Some PNG files (e.g. wikipedia drawings) open in PWP with black background and faint gray lettering/lines (while originally and in preview they are black on white). They import normally into e.g. Word. What can be causing it?

[MikeG]

Here's an example of a screen shot of this Wiki page:
http://en.wikipedia.org/wiki/Image_sensor_format
and the corresponding PWP 5.0 pasted image.

Vista Home Premium - freshly re-installed today!

Mike.

Wikipng[1].JPG (9.79 KiB) Viewed 3825 times

[HanSch]

Mike,

If I click on the .png picture in your link, I get a grey checkerboard pattern as background similar to that in e.g. Photoshop. This suggests, that the .png consists of more than one layer. I see an identical pattern if I open (many) .pdf's in Photoshop to rasterize them.
The image sensor picture also opens in Photoshop as a multilayer image. If you flatten the image, the checkerboard pattern is gone and the image is as in the original web page.
I suppose that PWP reacts in a similar way. The background in PWP 5.0 is apparently black.

Han

[Dieter Mayr]

Looks like they are PNGs with transperency channel, and that transperency channel is displayed black in PWP.
http://en.wikipedia.org/wiki/Portable_Network_Graphics
The picture with the cubes in the above article also shows black background when opening in PWP.
I do not know of any way to extract that transperency channel in PWP now, but it should be relatively easy to create a mask from the pure black parts and then add any desired background.

[keithrj]

I downloaded the PNG file of sensor sizes and looked at it in a number of programs that do not support he Alpha channel (transparent channel) and they all displayed the image with a black background. If you load the file in the GIMP (free graphics program) there is a menu option: Layer | Transparency | Remove Alpha Channel. Selecting this removes the Alpha channel which returns the image to normal with a white background. Save as a new file and all is well.

As an aside, I have been asking for a number of years for support for the Alpha Channel. I was hoping to be able to store masks in the transparency layer in supported file formats: PNG, TIFF, GIF and BMP.