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Amine27 is offline Amine27
2012-04-20 , 21:09
Posts: 11 | Thanked: 20 times | Joined on Nov 2011
#1
Hi,

Trying to use a background image that have a gradient with QML Image element gives a bad quality in the phone, as in the screenshots bellow:

Original: http://db.tt/FGWEzXhn
In the phone: http://db.tt/3SDeDjT3

With both N9 and N950, the code used (with different options and test) :

Code:
Image {
        fillMode: Image.PreserveAspectCrop
        source: "images/bg.png"
        smooth: true
}
Can anybody help me with this ?
 
Fuzzillogic is offline Fuzzillogic
2012-04-20 , 21:19
Posts: 479 | Thanked: 1,284 times | Joined on Jan 2012 @ Enschede, The Netherlands
#2
I still am unsure whether the N9 supports true color (16.8 million) graphics. I've seen this banding-effect on more occasions. It might be affected by screen dimming as well.

You could try to use a 16bpp image but with dithering applied.
 
Amine27 is offline Amine27
2012-04-20 , 21:34
Posts: 11 | Thanked: 20 times | Joined on Nov 2011
#3
I forget to note that the N9 Gallery shows the image correctly, just in my application it show it like in the screenshot.
 
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pycage is offline pycage
2012-04-21 , 12:52
Posts: 3,404 | Thanked: 4,474 times | Joined on Oct 2005 @ Germany
#4
Originally Posted by Fuzzillogic View Post
I still am unsure whether the N9 supports true color (16.8 million) graphics. I've seen this banding-effect on more occasions.
No, it does not. Try dithering the image before displaying to get better results. I'm pretty sure the gallery applies some dithering to make photos look better on 16bpp.
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flopjoke is offline flopjoke
2012-04-21 , 16:59
Posts: 426 | Thanked: 374 times | Joined on Apr 2012 @ Middle East
#5
Originally Posted by pycage View Post
No, it does not. Try dithering the image before displaying to get better results. I'm pretty sure the gallery applies some dithering to make photos look better on 16bpp.
Actually, it does support full 16 million colors. Check here for more info: http://europe.nokia.com/find-product...specifications

You can't really apply dithering filters in real time in a mobile device. Especially not in gallery where you scroll through 8 MP images so fast. I think it's most likely due to the way the image is called by the OS. It looks more like a software problem rather than a hardware problem to me.
 
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CepiPerez is offline CepiPerez
2012-04-21 , 23:35
Posts: 1,023 | Thanked: 4,421 times | Joined on Feb 2010 @ Argentina
#6
Image gallery doesn't use qml
I bet it applies filters in qimage or something like that.
Try to do the same.
 
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pycage is offline pycage
2012-04-22 , 14:37
Posts: 3,404 | Thanked: 4,474 times | Joined on Oct 2005 @ Germany
#7
Originally Posted by flopjoke View Post
Actually, it does support full 16 million colors. Check here for more info: http://europe.nokia.com/find-product...specifications
If you want to believe marketing lies more than the actual information output of the display driver...

Originally Posted by flopjoke View Post
You can't really apply dithering filters in real time in a mobile device.
Of course you can. Dithering from 24bpp to 16bpp is not that CPU-intensive.
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dumpystig is offline dumpystig
2012-04-22 , 14:55
Posts: 464 | Thanked: 338 times | Joined on Feb 2011 @ UK, Northwest
#8
Originally Posted by pycage View Post
If you want to believe marketing lies more than the actual information output of the display driver
Which is.....?
 
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ZerionSeven is offline ZerionSeven
2012-04-22 , 16:03
Posts: 68 | Thanked: 84 times | Joined on Mar 2007 @ Lappeenranta, Finland
#9
The device is capable of 24-bit color, just configured to run at 16-bit depth.

Code:
~ # xdpyinfo | grep 'depth of root'
  depth of root window:    16 planes
Some time ago I tried changing the X configuration to make the device run at 24-bit depth and it "worked", but some parts of the UI didn't work and everything was much slower.

Anyway, I think you can use QImage::convertToFormat to get 16-bit with dithering.
 

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