[PATCH v4 1/3] libcamera: Add rectangle two-point constructor
Kieran Bingham
kieran.bingham at ideasonboard.com
Mon Sep 23 10:48:07 CEST 2024
Quoting Jacopo Mondi (2024-09-23 09:32:01)
> Hi Harvey
>
> On Thu, Sep 19, 2024 at 10:15:14PM GMT, Cheng-Hao Yang wrote:
> > Hi Jacopo,
> >
> > On Thu, Sep 19, 2024 at 7:27 PM Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > wrote:
> >
> > > Hi Harvey
> > >
> > > On Mon, Sep 16, 2024 at 09:24:23AM GMT, Jacopo Mondi wrote:
> > > > Hello
> > > >
> > > > On Mon, Sep 16, 2024 at 12:34:54PM GMT, Cheng-Hao Yang wrote:
> > > > > Hi Barnabás and Jacopo,
> > > > >
> > > > > On Mon, Sep 16, 2024 at 1:27 AM Barnabás Pőcze <pobrn at protonmail.com>
> > > wrote:
> > > > >
> > > > > > Hi
> > > > > >
> > > > > >
> > > > > > 2024. szeptember 5., csütörtök 10:35 keltezéssel, Jacopo Mondi <
> > > > > > jacopo.mondi at ideasonboard.com> írta:
> > > > > >
> > > > > > > Hi Barnabás
> > > > > > >
> > > > > > > On Wed, Sep 04, 2024 at 11:26:37AM GMT, Barnabás Pőcze wrote:
> > > > > > > > Hi
> > > > > > > >
> > > > > > > >
> > > > > > > > 2024. szeptember 3., kedd 13:39 keltezéssel, Harvey Yang <
> > > > > > chenghaoyang at chromium.org> írta:
> > > > > > > >
> > > > > > > > > From: Yudhistira Erlandinata <yerlandinata at chromium.org>
> > > > > > > > >
> > > > > > > > > Add a Rectangle constructor that accepts two points:
> > > > > > > > > topLeft and bottomRight.
> > > > > > > > >
> > > > > > > > > Signed-off-by: Yudhistira Erlandinata <
> > > yerlandinata at chromium.org>
> > > > > > > > > Co-developed-by: Harvey Yang <chenghaoyang at chromium.org>
> > > > > > > > > Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > > > > > > > > ---
> > > > > > > > > include/libcamera/geometry.h | 2 ++
> > > > > > > > > src/libcamera/geometry.cpp | 14 ++++++++++++++
> > > > > > > > > 2 files changed, 16 insertions(+)
> > > > > > > > >
> > > > > > > > > diff --git a/include/libcamera/geometry.h
> > > > > > b/include/libcamera/geometry.h
> > > > > > > > > index 3e6f0f5d7..dc56f180f 100644
> > > > > > > > > --- a/include/libcamera/geometry.h
> > > > > > > > > +++ b/include/libcamera/geometry.h
> > > > > > > > > @@ -262,6 +262,8 @@ public:
> > > > > > > > > {
> > > > > > > > > }
> > > > > > > > >
> > > > > > > > > + constexpr Rectangle(const Point &topLeft, const Point
> > > > > > &bottomRight);
> > > > > > > >
> > > > > > > > Don't make this `constexpr` because it is not useful since the
> > > > > > definition is not available.
> > > > > > >
> > > > > > > I found references online that constexpr constuctors are implcitly
> > > > > > > inline, is this the reason of your comment ?
> > > > > >
> > > > > > Yes.
> > > > > >
> > > > > >
> > > > > > >
> > > > > > > However, I can't find it clearly specified in cppreference. Do you
> > > > > > > have any pointer ?
> > > > > >
> > > > > > "A constexpr specifier used in a function or static data
> > > member(since
> > > > > > C++17) declaration implies inline."
> > > > > > -- https://en.cppreference.com/w/cpp/language/constexpr
> > > > > >
> > > >
> > > >
> > > > One day I'll lear to read properly
> > > >
> > > > > > >
> > > > > > > Anyway, if inline is the reason, isn't it better to inline the
> > > > > > > definition and maintain the constexpr specifier ?
> > > > > > > [...]
> > > > > >
> > > > > > That is an option as well.
> > > > > >
> > > > >
> > > > > IIUC, you're suggesting to put the definition of the new c'tor
> > > > > back in the header file? As we use `ASSERT` in this c'tor
> > > > > definition, there will be a compile error if we do that:
> > > > > ```
> > > > >
> > > > > In file included from ../include/libcamera/base/log.h:12,
> > > > >
> > > > > from ../include/libcamera/geometry.h:16,
> > > > >
> > > > > from ../include/libcamera/controls.h:21,
> > > > >
> > > > > from ../include/libcamera/camera.h:22,
> > > > >
> > > > > from ../src/apps/common/dng_writer.h:13,
> > > > >
> > > > > from ../src/apps/common/dng_writer.cpp:8:
> > > > >
> > > > > ../include/libcamera/base/private.h:21:2: error: #error "Private
> > > headers
> > > > > must not be included in the libcamera API"
> > > > >
> > > > > 21 | #error "Private headers must not be included in the libcamera
> > > API"
> > > > > ```
> > > >
> > > > I see. log.h is private, and the fact ASSERT is not exposed in the
> > > > public API makes me think aborting execution on an invalid user input
> > > > is probably not the best idea ? That's maybe the reason why ASSERT is not
> > > > exposed to the public API ?
> > > >
> > >
> > > Assuming the top-left corner is always defined as the point with the
> > > smaller 'x' and the higher 'y' whatever the reference system the
> > > rectangle is placed in:
> > >
> > > In example:
> > >
> > > (0,0)
> > > -------------------------------->
> > > |
> > > | -------------------
> > > | | |
> > > | | |
> > > | x------------------
> > > |
> > > V
> > >
> > > Or:
> > >
> > > ^
> > > |
> > > |
> > > | x------------------
> > > | | |
> > > | | |
> > > | -------------------
> > > |
> > > |
> > > -------------------------------->
> > > (0,0)
> > >
> > > The assertion you have introduced in your proposed constructor
> > >
> > > constexpr Rectangle(const Point &topLeft, const Point &bottomRight)
> > > : x(topLeft.x), y(topLeft.y),
> > > width(bottomRight.x - x),
> > > height(bottomRight.y - y)
> > > {
> > > ASSERT(bottomRight.x >= x && bottomRight.y >= y);
> > > }
> > >
> > > is wrong as bottomRight.y shall always be smaller than topLeft.y
> > >
> > > Has this code been ever run ?
> > >
> >
> > Sorry for the confusion, but the `topLeft` point is actually somewhere
> > like this:
> >
> > (0,0)
> > -------------------------------->
> > |
> > | x-----------------
> > | | |
> > | | |
> > | -------------------
> > |
> > V
> >
> > `top-left` is (0, 0) in Android metadata's description [1], and it seems
> > that
> > it's also in libcamera's description to indicate a point with smaller x and
> > y coordinates [2].
> >
> > [1]:
> > https://android.googlesource.com/platform/system/media/+/refs/heads/main/camera/docs/docs.html#33019
> > [2]:
> > https://git.libcamera.org/libcamera/libcamera.git/tree/src/libcamera/geometry.cpp#n639
>
> Is this because of
>
> /**
> * \fn Rectangle::Rectangle(const Size &size)
> * \brief Construct a Rectangle of \a size with its top left corner located
> * at (0,0)
>
> This clearly doesn't match this case
>
> ^
> |
> |
> | x------------------
> | | |
> | | |
> | -------------------
> |
> |
> -------------------------------->
> (0,0)
>
> Maybe we have been a bit short-sighted and only assumed the blelow
> reference system had to be taken into account.
>
> (0,0)
> -------------------------------->
> |
> | x-----------------
> | | |
> | | |
> | -------------------
> |
> V
>
> Personally I would remove this assumption in our doc and define the
> top-left corner as the point with smaller x and largest y
>
> Opinions from libcamera people ?
Aha, I would define top left as 0,0 :-)
I've just opened up GIMP which also uses top left origin.
I expect other image applications would also honour this - so worth
checking a few ...
For me - even though this is 'geometry' ... it's *image processing*
geometry.
--
Kieran
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