ShowImage (or BMP translator) convert from PNG to BMP result in a drawing issue

[Giova84]

When i open an PNG image containing alpha channel and i convert this image to BMP, the resulting file contain drawing issues showed in the screenshot. hrev44384

[Giova84]

As in this ticket: https://dev.haiku-os.org/ticket/8781 i guess that ShowImage doesn't handle correctly alpha channel.

[X512]

I see that alpha channel is dropped. It happens because origional BMP format don't support alpha channel so Haiku translator can't use it. But newer versions of format and some programs (including internal windows programs line logonui.exe) using bitmaps with alpha channel.

[hometue]

(GCI-2012 Participant) Haiku revision: hrev44702. Not valid, but the transparent portion will be filled with a solid color, while the semi-transparent portion will become a solid version of the same color. System: Haiku R1-alpha4 on Virtualbox 4.1.20 on windows 7 64 bit

[pulkomandy]

Currently the background is properly cleared to white in that case, which sounds like a reasonable solution. We could extend the BMP translator to fully support alpha now, as it is available in version 3, 4 and 5 of the header: ​http://msdn.microsoft.com/en-us/library/dd183380(VS.85).aspx ​http://msdn.microsoft.com/en-us/library/dd183381(v=vs.85).aspx

But it seems not all applications can handle this... Closing the ticket as there is no bug here, only missing functionalities in the BMP translator.

[phoudoin]

Or turn this ticket into a low priority enhancement ticket renamed to "Add BMPv3+ alpha channel support to BMPTranslator", keeping it on the backlog.