[{"id":27983,"web_url":"https://patchwork.libcamera.org/comment/27983/","msgid":"<20231018202816.GI1512@pendragon.ideasonboard.com>","date":"2023-10-18T20:28:16","subject":"Re: [libcamera-devel] [PATCH v5 07/12] libcamera: transform: Add\n\toperations with Orientation","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Jacopo,\n\nThank you for the patch.\n\nOn Fri, Sep 01, 2023 at 05:02:10PM +0200, Jacopo Mondi via libcamera-devel wrote:\n> Add two operations that allows to combine Transform with Orientation.\n> \n> - Transform operator/(Orientation1, Orientation2)\n\nLet's write valid C++ code here:\n\n\tTransform operator/(const Orientation &o1, const Orientation &o2);\n\n> allows to easily get back the Transform that needs to be applied to\n> Orientation2 to get Orientation1\n> \n> - Orientation operator*(Orientation1, Transform)\n> allows to apply a Transform to an Orientation and obtain the\n> combination of the two\n\nAs commented in 06/12, this could be\n\n\tOrientation operator()(const Orientation &o);\n\nThe downside is that the division operator won't be the natural inverse\noperation. There's no easy shorthand notation for inverting a function\ncall. It may not be much of an issue though.\n\n> These two operations allow applications to use Transforms to\n> manipulate the Orientation inside the CameraConfiguration, if they\n> wish.\n\nI'll restate what I mentioned in what was (I think) a face to face\nconversation, to avoid future surprises. Once we'll have a C API, I\nexpect these convenience helpers (as well as the geometry helpers for\ninstance) to be dropped from the libcamera official C ABI. We could\nstill provide them to applications as part of the C++ bindings though.\n\n> Signed-off-by: Jacopo Mondi \n> Reviewed-by: David Plowman \n> ---\n> include/libcamera/transform.h | 3 +++\n> src/libcamera/transform.cpp | 37 +++++++++++++++++++++++++++++++++++\n> 2 files changed, 40 insertions(+)\n> \n> diff --git a/include/libcamera/transform.h b/include/libcamera/transform.h\n> index 14f1db0e8572..847a1f94713c 100644\n> --- a/include/libcamera/transform.h\n> +++ b/include/libcamera/transform.h\n> @@ -74,6 +74,9 @@ Transform transformFromRotation(int angle, bool *success = nullptr);\n> Transform transformFromOrientation(const Orientation &orientation);\n> Orientation transformToOrientation(const Transform &transform);\n> \n> +Transform operator/(const Orientation &o1, const Orientation &o2);\n> +Orientation operator*(const Orientation &o1, const Transform &t);\n> +\n> const char *transformToString(Transform t);\n> \n> } /* namespace libcamera */\n> diff --git a/src/libcamera/transform.cpp b/src/libcamera/transform.cpp\n> index d192d63d9290..80cd804ca530 100644\n> --- a/src/libcamera/transform.cpp\n> +++ b/src/libcamera/transform.cpp\n> @@ -362,6 +362,43 @@ Orientation transformToOrientation(const Transform &transform)\n> \treturn Orientation::rotate0;\n> }\n> \n> +/**\n> + * \\brief Return the Transform that applied to \\a o2 gives \\a o1\n> + * \\param o1 The Orientation to obtain\n> + * \\param o2 The base Orientation\n> + *\n> + * This operation can be used to easily compute the Transform to apply to a\n> + * base orientation \\a o2 to get the desired orientation \\a o1.\n> + *\n> + * The CameraSensor class uses this function to compute what Transform to apply\n> + * to a camera with mounting rotation \\a o2 (the base) to obtain the user\n> + * requested orientation \\a o1.\n\nI would drop this paragraph, it's an internal implementation detail, and\nthe CameraSensor class is not part of the public API.\n\n> + *\n> + * \\return A Transform that applied to \\a o2 gives \\a o1\n> + */\n> +Transform operator/(const Orientation &o1, const Orientation &o2)\n> +{\n> +\tTransform t1 = transformFromOrientation(o1);\n> +\tTransform t2 = transformFromOrientation(o2);\n> +\n> +\treturn -t2 * t1;\n> +}\n> +\n> +/**\n> + * \\brief Apply the Transform \\a t on the base orientation \\a o\n\ns/base //\n\n> + * \\param o The base orientation\n\ns/base //\n\n> + * \\param t The transform to apply on \\a o\n> + * \\return The Orientation resulting from applying \\a t on \\a o\n> + */\n> +Orientation operator*(const Orientation &o, const Transform &t)\n> +{\n> +\t/*\n> +\t * Apply a Transform corresponding to the base orientation first and\n> +\t * then apply \\a t to it.\n> +\t */\n> +\treturn transformToOrientation(transformFromOrientation(o) * t);\n> +}\n> +\n> /**\n> * \\brief Return a character string describing the transform\n> * \\param[in] t The transform to be described.\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id A2297BDCBD\n\tfor ;\n\tWed, 18 Oct 2023 20:28:11 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id E078D6297F;\n\tWed, 18 Oct 2023 22:28:10 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 400B761DD1\n\tfor ;\n\tWed, 18 Oct 2023 22:28:10 +0200 (CEST)","from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi\n\t[213.243.189.158])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 8A8C3666;\n\tWed, 18 Oct 2023 22:28:02 +0200 (CEST)"],"DKIM-Signature":["v=1; 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