On Thu, Jan 16, 2025 at 12:33:20PM +0000, Murthy, Arun R wrote:
> > > > On Fri, Jan 10, 2025 at 01:15:29AM +0530, Arun R Murthy wrote:
> > > > > Display Histogram is an array of bins and can be generated in many
> > > > > ways referred to as modes.
> > > > > Ex: HSV max(RGB), Wighted RGB etc.
> > > > >
> > > > > Understanding the histogram data format(Ex: HSV max(RGB))
> > > > > Histogram is just the pixel count.
> > > > > For a maximum resolution of 10k (10240 x 4320 = 44236800)
> > > > > 25 bits should be sufficient to represent this along with a buffer
> > > > > of
> > > > > 7 bits(future use) u32 is being considered.
> > > > > max(RGB) can be 255 i.e 0xFF 8 bit, considering the most
> > > > > significant 5 bits, hence 32 bins.
> > > > > Below mentioned algorithm illustrates the histogram generation in
> > > > > hardware.
> > > > >
> > > > > hist[32] = {0};
> > > > > for (i = 0; i < resolution; i++) {
> > > > > bin = max(RGB[i]);
> > > > > bin = bin >> 3; /* consider the most significant bits */
> > > > > hist[bin]++;
> > > > > }
> > > > > If the entire image is Red color then max(255,0,0) is 255 so the
> > > > > pixel count of each pixels will be placed in the last bin. Hence
> > > > > except hist[31] all other bins will have a value zero.
> > > > > Generated histogram in this case would be hist[32] =
> > > > > {0,0,....44236800}
> > > > >
> > > > > Description of the structures, properties defined are documented
> > > > > in the header file include/uapi/drm/drm_mode.h
> > > > >
> > > > > Signed-off-by: Arun R Murthy <arun.r.murthy@xxxxxxxxx>
> > > > > ---
> > > > > include/uapi/drm/drm_mode.h | 59
> > > > > +++++++++++++++++++++++++++++++++++++++++++++
> > > > > 1 file changed, 59 insertions(+)
> > > > >
> > > > > diff --git a/include/uapi/drm/drm_mode.h
> > > > > b/include/uapi/drm/drm_mode.h index
> > > > >
> > > >
> > c082810c08a8b234ef2672ecf54fc8c05ddc2bd3..7a7039381142bb5dba269bda
> > > > ec42
> > > > > c18be34e2d05 100644
> > > > > --- a/include/uapi/drm/drm_mode.h
> > > > > +++ b/include/uapi/drm/drm_mode.h
> > > > > @@ -1355,6 +1355,65 @@ struct drm_mode_closefb {
> > > > > __u32 pad;
> > > > > };
> > > > >
> > > > > +/*
> > > > > + * Maximum resolution at present 10k, 10240x4320 = 44236800
> > > > > + * can be denoted in 25bits. With an additional 7 bits in buffer
> > > > > +each bin
> > > > > + * can be a u32 value.
> > > > > + * Maximum value of max(RGB) is 255, so max 255 bins.
> > > >
> > > > HDR planes have higher max value for a component.
> > > > Likewise even in an RGB24 case there are 256 possible values. It's
> > > > not clear why
> > > > 0 gets excluded.
> > > >
> > > This applies to only SDR and excludes HDR.
> >
> > Why?
> >
> We are limiting to only SDR. HDR includes a broad range of color and finer details,
> which essentially means its an enhanced image.
> We are trying to enhance the image quality of SDR with the support of histogram.
You are defining generic API. It might be broader than your existing
usecase. Please consider supporting HDR too.
> > > RGB in hex can have a maximum value of 0xFF { RGB (255, 255, 255) }
> > >
--
With best wishes
Dmitry
