Created attachment 140962 [details] images gamma I have a PC with: MB: Asrock AM1B-ITX CPU: AMD Kabini Athlon 5350 APU iGPU: Radeon HD 8400 / R3 Series Displays: DVI Asus, HDMI Samsung kernel-4.15/4.16/4.17 xorg-server-1.19.5 xorg-drivers-1.19 xf86-video-amdgpu-18.0.1 xf86-video-ati-18.0.1 libdrm-2.4.92 When I increase the gamma to check the quality of images (xgamma -gamma 3), some pixels are darker/colorful, it seems like gamma is not applied uniformly for all pixels. This happens on all kernels with any video driver: radeon, amdgpu, amdgpu-dc. I thought there's something wrong with the images so I've edited them on Gimp by increasing brightness or change hue/saturation. This was fine until the kernel 4.17 and the amdgpu-dc driver upgrade, images have again the issue. They are fine with amdgpu. Is there something I can do about this? Thanks.
Please attach the corresponding Xorg log file. How did you capture the attached image? Can you also attach a corresponding direct capture with a screenshot tool on that machine?
Created attachment 140974 [details] xorg log
Created attachment 140975 [details] imagemagick original capture These are the capture commands (ImageMagick) used with FVWM: import -window $[w.id] -silent "PNG24:$[infostore.mScreenshots]/screenshot-$(date +%F[%R]).png" import -window root -silent "PNG24:$[infostore.mScreenshots]/screenshot-$(date +%F[%R]).png" Attached the original capture (without gamma). For the first attached imaged I've applied gamma with Gimp.
(In reply to Sebastian Luncan from comment #3) > For the first attached imaged I've applied gamma with Gimp. How exactly did you do that? Anyway, I don't think there's a bug here. Gamma doesn't affect all colour values the same way (in particular, 0 and the maximum value are preserved for each colour component). The "colourful" pixels occur because the original pixels have 0 or a very small value in some components but larger values in others, which are affected differently by gamma.
Created attachment 141147 [details] Gamma amdgpu vs amdgpu-dc I don't know how to capture the screen with gamma so I did a capture with imagemagick and applied gamma with gimp so the issues are visible. I've also took a picture (attached). On the left is amdgpu-dc on the right amdgpu, gamma 3 (xgamma -gamma 3), kernel 4.17. See the trees and the grass on the left. Why do they look different on the same gamma values? As I said, this happened before and I've fixed the issue with gimp by changing images brightness and hue/saturation, but now with amdgpu-dc from 4.17 the issues are back.
(In reply to Sebastian Luncan from comment #5) > I've also took a picture (attached). On the left is amdgpu-dc on the right > amdgpu, gamma 3 (xgamma -gamma 3), kernel 4.17. See the trees and the grass > on the left. Why do they look different on the same gamma values? Can you try if current upstream xf86-video-amdgpu Git master works better with DC?
(In reply to Michel Dänzer from comment #6) > Can you try if current upstream xf86-video-amdgpu Git master works better > with DC? It's the same. I've also tried videos with gamma 3. All hardware decoded videos (h264) look fine, software decoded have this issue.
Leo, any ideas what's going on here?
Michel's right about xgamma leaving 0 and max per-channel values unmodified, so the original issue is not-a-bug. Although I'm not sure why there's a difference between amdgpu and dc, I'll have to look into it.
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