Atlas - read-and-draw.c
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[FILE BEGIN]
1/*
2 * This example code reads frames from a camera and draws it to the screen.
3 *
4 * This is a very simple approach that is often Good Enough. You can get
5 * fancier with this: multiple cameras, front/back facing cameras on phones,
6 * color spaces, choosing formats and framerates...this just requests
7 * _anything_ and goes with what it is handed.
8 *
9 * This code is public domain. Feel free to use it for any purpose!
10 */
11
12#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
13#include <SDL3/SDL.h>
14#include <SDL3/SDL_main.h>
15
16/* We will use this renderer to draw into this window every frame. */
17static SDL_Window *window = NULL;
18static SDL_Renderer *renderer = NULL;
19static SDL_Camera *camera = NULL;
20static SDL_Texture *texture = NULL;
21
22
23/* This function runs once at startup. */
24SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
25{
26    SDL_CameraID *devices = NULL;
27    int devcount = 0;
28
29    SDL_SetAppMetadata("Example Camera Read and Draw", "1.0", "com.example.camera-read-and-draw");
30
31    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_CAMERA)) {
32        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
33        return SDL_APP_FAILURE;
34    }
35
36    if (!SDL_CreateWindowAndRenderer("examples/camera/read-and-draw", 640, 480, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
37        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
38        return SDL_APP_FAILURE;
39    }
40
41    devices = SDL_GetCameras(&devcount);
42    if (devices == NULL) {
43        SDL_Log("Couldn't enumerate camera devices: %s", SDL_GetError());
44        return SDL_APP_FAILURE;
45    } else if (devcount == 0) {
46        SDL_Log("Couldn't find any camera devices! Please connect a camera and try again.");
47        SDL_free(devices);
48        return SDL_APP_FAILURE;
49    }
50
51    camera = SDL_OpenCamera(devices[0], NULL);  // just take the first thing we see in any format it wants.
52    SDL_free(devices);
53    if (camera == NULL) {
54        SDL_Log("Couldn't open camera: %s", SDL_GetError());
55        return SDL_APP_FAILURE;
56    }
57
58    return SDL_APP_CONTINUE;  /* carry on with the program! */
59}
60
61/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
62SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
63{
64    if (event->type == SDL_EVENT_QUIT) {
65        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
66    } else if (event->type == SDL_EVENT_CAMERA_DEVICE_APPROVED) {
67        SDL_Log("Camera use approved by user!");
68    } else if (event->type == SDL_EVENT_CAMERA_DEVICE_DENIED) {
69        SDL_Log("Camera use denied by user!");
70        return SDL_APP_FAILURE;
71    }
72    return SDL_APP_CONTINUE;  /* carry on with the program! */
73}
74
75/* This function runs once per frame, and is the heart of the program. */
76SDL_AppResult SDL_AppIterate(void *appstate)
77{
78    Uint64 timestampNS = 0;
79    SDL_Surface *frame = SDL_AcquireCameraFrame(camera, &timestampNS);
80
81    if (frame != NULL) {
82        /* Some platforms (like Emscripten) don't know _what_ the camera offers
83           until the user gives permission, so we build the texture and resize
84           the window when we get a first frame from the camera. */
85        if (!texture) {
86            SDL_SetWindowSize(window, frame->w, frame->h);  /* Resize the window to match */
87            SDL_SetRenderLogicalPresentation(renderer, frame->w, frame->h, SDL_LOGICAL_PRESENTATION_LETTERBOX);
88            texture = SDL_CreateTexture(renderer, frame->format, SDL_TEXTUREACCESS_STREAMING, frame->w, frame->h);
89        }
90
91        if (texture) {
92            SDL_UpdateTexture(texture, NULL, frame->pixels, frame->pitch);
93        }
94
95        SDL_ReleaseCameraFrame(camera, frame);
96    }
97
98    SDL_SetRenderDrawColor(renderer, 0x99, 0x99, 0x99, SDL_ALPHA_OPAQUE);
99    SDL_RenderClear(renderer);
100    if (texture) {  /* draw the latest camera frame, if available. */
101        SDL_RenderTexture(renderer, texture, NULL, NULL);
102    }
103    SDL_RenderPresent(renderer);
104
105    return SDL_APP_CONTINUE;  /* carry on with the program! */
106}
107
108/* This function runs once at shutdown. */
109void SDL_AppQuit(void *appstate, SDL_AppResult result)
110{
111    SDL_CloseCamera(camera);
112    SDL_DestroyTexture(texture);
113    /* SDL will clean up the window/renderer for us. */
114}
115
116
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