nanogui: PNG and transparency
Subject:
RE: [nanogui] PNG and transparency
From:
BRACH Vincent ####@####.####
Date:
28 Jul 2009 09:12:43 -0000
Message-Id: <1248684675.5326.20.camel@zoul.intranet.smie.com>
Hello Steven, and thanks for your message,
> I have also experienced this issue. I was able to work around it by editing the PNG file.
>
> If you open your PNG file in an editor (I used The GIMP) and click on the area that is supposed to be transparent with the color-picker tool, you'll probably see that the RGB color values are:
>
> R: 0
> G: 0
> B: 0
> Alpha: 0
>
> In order for regions to appear transparent in nano-X you need to change the RGB values for the transparent area to:
>
> R: 255
> G: 255
> B: 255
> Alpha: 0
I done some tests and I noticed some funny results : First time I used
the 0.91 :
With the "0.91" version I noticed that PNG image with RGB=0,0,0 and
Alpha=0 for transparent color was display in black (not transparent) but
PNG image with RGB=255,255,255 and Alpha=0 (or no alpha) for transparent
color was diplay with ritght transparent at this part.
After I download nano-X sources from the CVS repository Version "pre
0.92" and I noticed that there's a different comportment :
An image PNG with RGB=0,0,0 (or RGB=255,255,255) and Alpha=0 for
transparent color was right display, but normaly an image with
RGB=255,255,255 and no Alpha was display in white for parts (and not
with transparent colors). Maybe there's several difference between the
0.91 and the "pre 0.92"...
Anyway I work now with the last CVS version (pre 0.92), but this
difference is strange. Maybe a fixed bug ?
Any colors informations was took with gimp·
> (In fact, I think any region in a PNG that has a RGB value of (255,255,255) will appear transparent, even if the alpha value isn't 0.)
Right ! It's that what I noticed for the 0.91 version (but not with pre
0.92). With this last version alpha seems to be set.
> I am not experienced with photo editors, and I had to try several of them before I found one where I could figure out how to modify the RGB values of the transparent region. Without going step-by-step, I was able to do this in The GIMP by selecting the transparent region by color, replacing its color with pure white (255,255,255), and then making the region clear again.
>
> I'm not super experienced with nano-X so maybe someone else out there has a simpler way to fix this problem. But I hope this is helpful anyway.
Thanks again,
> Steven Vahl
Regards,
Vincent BRACH
