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sebaro
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PostPosted: Tue Jul 31, 2018 7:14 am    Post subject: Different gamma rendering between kernels Reply with quote

I have a PC with AMD Kabini APU using amdgpu-dc driver. I've upgraded kernel from 4.16 to 4.17. The problem is with the images gamma rendering and 4.17. When I increase the display gamma (xgamma) above 2.5, some images look bad, many pixels look darker than they should be, seems like gamma is not applied to all pixels uniformly. The same images look fine with radeon and amdgpu drivers from 4.17 or older kernels.

Gamma with amdgpu-dc:
https://image.ibb.co/mzQXoo/gamma_amdgpu_dc.jpg

Gamma with amdgpu-nondc:
https://image.ibb.co/iaVMg8/gamma_amdgpu_nondc.jpg

Is there a problem with the images, can I do something so they look the same on any video hardware/software or gamma rendering depends entirely on these?

Thanks.
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mike155
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PostPosted: Tue Jul 31, 2018 5:06 pm    Post subject: Reply with quote

Sebaro:

1) Where do you set the gamma value to 2.5? In your video card? Or is it a setting in your TFT monitor?

2) How is your monitor connected to your graphics card? VGA? DVI? HDMI?
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Ant P.
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PostPosted: Tue Jul 31, 2018 5:50 pm    Post subject: Reply with quote

amdgpu added some sort of color profile support in 4.17 (it shows up in xrandr --prop if you have a new enough xf86-video-amdgpu), I'm not sure how it's meant to be used but I'd look there first.
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sebaro
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PostPosted: Tue Jul 31, 2018 7:36 pm    Post subject: Reply with quote

mike155 wrote:

1) Where do you set the gamma value to 2.5? In your video card? Or is it a setting in your TFT monitor?
2) How is your monitor connected to your graphics card? VGA? DVI? HDMI?

1. xgamma -gamma 2.5
2. DVI
Ant P. wrote:

amdgpu added some sort of color profile support in 4.17 (it shows up in xrandr --prop if you have a new enough xf86-video-amdgpu), I'm not sure how it's meant to be used but I'd look there first.

I've found something about color management but I don't know what that means.

I had this problem with images before. I had to increase the images brightness or change hue/saturation to make them look good on gamma 2.5 or above. But now this kernel upgrade made them look bad again.
So, all I want to know if there's something wrong with the images, is there a setting that I have to use when exporting to PNG so this doesn't happen when drivers get changed.
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