SDL/include/SDL3/SDL_camera.h

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

/**
 * # CategoryCamera
 *
 * Video capture for the SDL library.
 *
 * This API lets apps read input from video sources, like webcams. Camera
 * devices can be enumerated, queried, and opened. Once opened, it will
 * provide SDL_Surface objects as new frames of video come in. These surfaces
 * can be uploaded to an SDL_Texture or processed as pixels in memory.
 *
 * ## Camera gotchas
 *
 * Consumer-level camera hardware tends to take a little while to warm up,
 * once the device has been opened. Generally most camera apps have some sort
 * of UI to take a picture (a button to snap a pic while a preview is showing,
 * some sort of multi-second countdown for the user to pose, like a photo
 * booth), which puts control in the users' hands, or they are intended to
 * stay on for long times (Pokemon Go, etc).
 *
 * It's not uncommon that a newly-opened camera will provide a couple of
 * completely black frames, maybe followed by some under-exposed images. If
 * taking single frame automatically, or recording video from a camera's input
 * without the user initiating it from a preview, it could be wise to drop the
 * first several frames (if not the first several _seconds_ worth of frames!)
 * before using images from a camera.
 */

#ifndef SDL_camera_h_
#define SDL_camera_h_

#include <SDL3/SDL_stdinc.h>
#include <SDL3/SDL_error.h>
#include <SDL3/SDL_pixels.h>
#include <SDL3/SDL_properties.h>
#include <SDL3/SDL_surface.h>

#include <SDL3/SDL_begin_code.h>
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
extern "C" {
#endif

/**
 * This is a unique ID for a camera device for the time it is connected to the
 * system, and is never reused for the lifetime of the application.
 *
 * If the device is disconnected and reconnected, it will get a new ID.
 *
 * The value 0 is an invalid ID.
 *
 * \since This datatype is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameras
 */
typedef Uint32 SDL_CameraID;

/**
 * The opaque structure used to identify an opened SDL camera.
 *
 * \since This struct is available since SDL 3.1.3.
 */
typedef struct SDL_Camera SDL_Camera;

/**
 * The details of an output format for a camera device.
 *
 * Cameras often support multiple formats; each one will be encapsulated in
 * this struct.
 *
 * \since This struct is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameraSupportedFormats
 * \sa SDL_GetCameraFormat
 */
typedef struct SDL_CameraSpec
{
    SDL_PixelFormat format;     /**< Frame format */
    SDL_Colorspace colorspace;  /**< Frame colorspace */
    int width;                  /**< Frame width */
    int height;                 /**< Frame height */
    int framerate_numerator;     /**< Frame rate numerator ((num / denom) == FPS, (denom / num) == duration in seconds) */
    int framerate_denominator;   /**< Frame rate demoninator ((num / denom) == FPS, (denom / num) == duration in seconds) */
} SDL_CameraSpec;

/**
 * The position of camera in relation to system device.
 *
 * \since This enum is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameraPosition
 */
typedef enum SDL_CameraPosition
{
    SDL_CAMERA_POSITION_UNKNOWN,
    SDL_CAMERA_POSITION_FRONT_FACING,
    SDL_CAMERA_POSITION_BACK_FACING
} SDL_CameraPosition;


/**
 * Use this function to get the number of built-in camera drivers.
 *
 * This function returns a hardcoded number. This never returns a negative
 * value; if there are no drivers compiled into this build of SDL, this
 * function returns zero. The presence of a driver in this list does not mean
 * it will function, it just means SDL is capable of interacting with that
 * interface. For example, a build of SDL might have v4l2 support, but if
 * there's no kernel support available, SDL's v4l2 driver would fail if used.
 *
 * By default, SDL tries all drivers, in its preferred order, until one is
 * found to be usable.
 *
 * \returns the number of built-in camera drivers.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameraDriver
 */
extern SDL_DECLSPEC int SDLCALL SDL_GetNumCameraDrivers(void);

/**
 * Use this function to get the name of a built in camera driver.
 *
 * The list of camera drivers is given in the order that they are normally
 * initialized by default; the drivers that seem more reasonable to choose
 * first (as far as the SDL developers believe) are earlier in the list.
 *
 * The names of drivers are all simple, low-ASCII identifiers, like "v4l2",
 * "coremedia" or "android". These never have Unicode characters, and are not
 * meant to be proper names.
 *
 * \param index the index of the camera driver; the value ranges from 0 to
 *              SDL_GetNumCameraDrivers() - 1.
 * \returns the name of the camera driver at the requested index, or NULL if
 *          an invalid index was specified.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetNumCameraDrivers
 */
extern SDL_DECLSPEC const char * SDLCALL SDL_GetCameraDriver(int index);

/**
 * Get the name of the current camera driver.
 *
 * The names of drivers are all simple, low-ASCII identifiers, like "v4l2",
 * "coremedia" or "android". These never have Unicode characters, and are not
 * meant to be proper names.
 *
 * \returns the name of the current camera driver or NULL if no driver has
 *          been initialized.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 */
extern SDL_DECLSPEC const char * SDLCALL SDL_GetCurrentCameraDriver(void);

/**
 * Get a list of currently connected camera devices.
 *
 * \param count a pointer filled in with the number of cameras returned, may
 *              be NULL.
 * \returns a 0 terminated array of camera instance IDs or NULL on failure;
 *          call SDL_GetError() for more information. This should be freed
 *          with SDL_free() when it is no longer needed.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_OpenCamera
 */
extern SDL_DECLSPEC SDL_CameraID * SDLCALL SDL_GetCameras(int *count);

/**
 * Get the list of native formats/sizes a camera supports.
 *
 * This returns a list of all formats and frame sizes that a specific camera
 * can offer. This is useful if your app can accept a variety of image formats
 * and sizes and so want to find the optimal spec that doesn't require
 * conversion.
 *
 * This function isn't strictly required; if you call SDL_OpenCamera with a
 * NULL spec, SDL will choose a native format for you, and if you instead
 * specify a desired format, it will transparently convert to the requested
 * format on your behalf.
 *
 * If `count` is not NULL, it will be filled with the number of elements in
 * the returned array.
 *
 * Note that it's legal for a camera to supply an empty list. This is what
 * will happen on Emscripten builds, since that platform won't tell _anything_
 * about available cameras until you've opened one, and won't even tell if
 * there _is_ a camera until the user has given you permission to check
 * through a scary warning popup.
 *
 * \param devid the camera device instance ID to query.
 * \param count a pointer filled in with the number of elements in the list,
 *              may be NULL.
 * \returns a NULL terminated array of pointers to SDL_CameraSpec or NULL on
 *          failure; call SDL_GetError() for more information. This is a
 *          single allocation that should be freed with SDL_free() when it is
 *          no longer needed.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameras
 * \sa SDL_OpenCamera
 */
extern SDL_DECLSPEC SDL_CameraSpec ** SDLCALL SDL_GetCameraSupportedFormats(SDL_CameraID devid, int *count);

/**
 * Get the human-readable device name for a camera.
 *
 * \param instance_id the camera device instance ID.
 * \returns a human-readable device name or NULL on failure; call
 *          SDL_GetError() for more information.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameras
 */
extern SDL_DECLSPEC const char * SDLCALL SDL_GetCameraName(SDL_CameraID instance_id);

/**
 * Get the position of the camera in relation to the system.
 *
 * Most platforms will report UNKNOWN, but mobile devices, like phones, can
 * often make a distinction between cameras on the front of the device (that
 * points towards the user, for taking "selfies") and cameras on the back (for
 * filming in the direction the user is facing).
 *
 * \param instance_id the camera device instance ID.
 * \returns the position of the camera on the system hardware.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameras
 */
extern SDL_DECLSPEC SDL_CameraPosition SDLCALL SDL_GetCameraPosition(SDL_CameraID instance_id);

/**
 * Open a video recording device (a "camera").
 *
 * You can open the device with any reasonable spec, and if the hardware can't
 * directly support it, it will convert data seamlessly to the requested
 * format. This might incur overhead, including scaling of image data.
 *
 * If you would rather accept whatever format the device offers, you can pass
 * a NULL spec here and it will choose one for you (and you can use
 * SDL_Surface's conversion/scaling functions directly if necessary).
 *
 * You can call SDL_GetCameraFormat() to get the actual data format if passing
 * a NULL spec here. You can see the exact specs a device can support without
 * conversion with SDL_GetCameraSupportedFormats().
 *
 * SDL will not attempt to emulate framerate; it will try to set the hardware
 * to the rate closest to the requested speed, but it won't attempt to limit
 * or duplicate frames artificially; call SDL_GetCameraFormat() to see the
 * actual framerate of the opened the device, and check your timestamps if
 * this is crucial to your app!
 *
 * Note that the camera is not usable until the user approves its use! On some
 * platforms, the operating system will prompt the user to permit access to
 * the camera, and they can choose Yes or No at that point. Until they do, the
 * camera will not be usable. The app should either wait for an
 * SDL_EVENT_CAMERA_DEVICE_APPROVED (or SDL_EVENT_CAMERA_DEVICE_DENIED) event,
 * or poll SDL_GetCameraPermissionState() occasionally until it returns
 * non-zero. On platforms that don't require explicit user approval (and
 * perhaps in places where the user previously permitted access), the approval
 * event might come immediately, but it might come seconds, minutes, or hours
 * later!
 *
 * \param instance_id the camera device instance ID.
 * \param spec the desired format for data the device will provide. Can be
 *             NULL.
 * \returns an SDL_Camera object or NULL on failure; call SDL_GetError() for
 *          more information.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_GetCameras
 * \sa SDL_GetCameraFormat
 */
extern SDL_DECLSPEC SDL_Camera * SDLCALL SDL_OpenCamera(SDL_CameraID instance_id, const SDL_CameraSpec *spec);

/**
 * Query if camera access has been approved by the user.
 *
 * Cameras will not function between when the device is opened by the app and
 * when the user permits access to the hardware. On some platforms, this
 * presents as a popup dialog where the user has to explicitly approve access;
 * on others the approval might be implicit and not alert the user at all.
 *
 * This function can be used to check the status of that approval. It will
 * return 0 if still waiting for user response, 1 if the camera is approved
 * for use, and -1 if the user denied access.
 *
 * Instead of polling with this function, you can wait for a
 * SDL_EVENT_CAMERA_DEVICE_APPROVED (or SDL_EVENT_CAMERA_DEVICE_DENIED) event
 * in the standard SDL event loop, which is guaranteed to be sent once when
 * permission to use the camera is decided.
 *
 * If a camera is declined, there's nothing to be done but call
 * SDL_CloseCamera() to dispose of it.
 *
 * \param camera the opened camera device to query.
 * \returns -1 if user denied access to the camera, 1 if user approved access,
 *          0 if no decision has been made yet.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_OpenCamera
 * \sa SDL_CloseCamera
 */
extern SDL_DECLSPEC int SDLCALL SDL_GetCameraPermissionState(SDL_Camera *camera);

/**
 * Get the instance ID of an opened camera.
 *
 * \param camera an SDL_Camera to query.
 * \returns the instance ID of the specified camera on success or 0 on
 *          failure; call SDL_GetError() for more information.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_OpenCamera
 */
extern SDL_DECLSPEC SDL_CameraID SDLCALL SDL_GetCameraID(SDL_Camera *camera);

/**
 * Get the properties associated with an opened camera.
 *
 * \param camera the SDL_Camera obtained from SDL_OpenCamera().
 * \returns a valid property ID on success or 0 on failure; call
 *          SDL_GetError() for more information.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 */
extern SDL_DECLSPEC SDL_PropertiesID SDLCALL SDL_GetCameraProperties(SDL_Camera *camera);

/**
 * Get the spec that a camera is using when generating images.
 *
 * Note that this might not be the native format of the hardware, as SDL might
 * be converting to this format behind the scenes.
 *
 * If the system is waiting for the user to approve access to the camera, as
 * some platforms require, this will return false, but this isn't necessarily
 * a fatal error; you should either wait for an
 * SDL_EVENT_CAMERA_DEVICE_APPROVED (or SDL_EVENT_CAMERA_DEVICE_DENIED) event,
 * or poll SDL_GetCameraPermissionState() occasionally until it returns
 * non-zero.
 *
 * \param camera opened camera device.
 * \param spec the SDL_CameraSpec to be initialized by this function.
 * \returns true on success or false on failure; call SDL_GetError() for more
 *          information.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_OpenCamera
 */
extern SDL_DECLSPEC bool SDLCALL SDL_GetCameraFormat(SDL_Camera *camera, SDL_CameraSpec *spec);

/**
 * Acquire a frame.
 *
 * The frame is a memory pointer to the image data, whose size and format are
 * given by the spec requested when opening the device.
 *
 * This is a non blocking API. If there is a frame available, a non-NULL
 * surface is returned, and timestampNS will be filled with a non-zero value.
 *
 * Note that an error case can also return NULL, but a NULL by itself is
 * normal and just signifies that a new frame is not yet available. Note that
 * even if a camera device fails outright (a USB camera is unplugged while in
 * use, etc), SDL will send an event separately to notify the app, but
 * continue to provide blank frames at ongoing intervals until
 * SDL_CloseCamera() is called, so real failure here is almost always an out
 * of memory condition.
 *
 * After use, the frame should be released with SDL_ReleaseCameraFrame(). If
 * you don't do this, the system may stop providing more video!
 *
 * Do not call SDL_DestroySurface() on the returned surface! It must be given
 * back to the camera subsystem with SDL_ReleaseCameraFrame!
 *
 * If the system is waiting for the user to approve access to the camera, as
 * some platforms require, this will return NULL (no frames available); you
 * should either wait for an SDL_EVENT_CAMERA_DEVICE_APPROVED (or
 * SDL_EVENT_CAMERA_DEVICE_DENIED) event, or poll
 * SDL_GetCameraPermissionState() occasionally until it returns non-zero.
 *
 * \param camera opened camera device.
 * \param timestampNS a pointer filled in with the frame's timestamp, or 0 on
 *                    error. Can be NULL.
 * \returns a new frame of video on success, NULL if none is currently
 *          available.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_ReleaseCameraFrame
 */
extern SDL_DECLSPEC SDL_Surface * SDLCALL SDL_AcquireCameraFrame(SDL_Camera *camera, Uint64 *timestampNS);

/**
 * Release a frame of video acquired from a camera.
 *
 * Let the back-end re-use the internal buffer for camera.
 *
 * This function _must_ be called only on surface objects returned by
 * SDL_AcquireCameraFrame(). This function should be called as quickly as
 * possible after acquisition, as SDL keeps a small FIFO queue of surfaces for
 * video frames; if surfaces aren't released in a timely manner, SDL may drop
 * upcoming video frames from the camera.
 *
 * If the app needs to keep the surface for a significant time, they should
 * make a copy of it and release the original.
 *
 * The app should not use the surface again after calling this function;
 * assume the surface is freed and the pointer is invalid.
 *
 * \param camera opened camera device.
 * \param frame the video frame surface to release.
 *
 * \threadsafety It is safe to call this function from any thread.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_AcquireCameraFrame
 */
extern SDL_DECLSPEC void SDLCALL SDL_ReleaseCameraFrame(SDL_Camera *camera, SDL_Surface *frame);

/**
 * Use this function to shut down camera processing and close the camera
 * device.
 *
 * \param camera opened camera device.
 *
 * \threadsafety It is safe to call this function from any thread, but no
 *               thread may reference `device` once this function is called.
 *
 * \since This function is available since SDL 3.1.3.
 *
 * \sa SDL_OpenCamera
 */
extern SDL_DECLSPEC void SDLCALL SDL_CloseCamera(SDL_Camera *camera);

/* Ends C function definitions when using C++ */
#ifdef __cplusplus
}
#endif
#include <SDL3/SDL_close_code.h>

#endif /* SDL_camera_h_ */