camtest: add webcam support

ThomasFarstrike · ThomasFarstrike · commit fa295e7f5756 · 2025-05-13T16:12:21.000+02:00
diff --git a/README.md b/README.md
@@ -107,7 +107,11 @@ Building for desktop
 ====================
 Building to run as an app on the Linux desktop or MacOS (untested) is supported.
 
-To do so, make sure you have the necessary dependencies (see https://github.com/lvgl-micropython/) and then run:
+To do so, make sure you have the necessary dependencies:
+- see https://github.com/lvgl-micropython/
+- sudo apt install libv4l-dev # for webcam.c
+
+...and then run:
 
 ```
 ~/sources/PiggyOS/scripts/build_lvgl_micropython.sh unix
diff --git a/c_mpos/src/webcam.c b/c_mpos/src/webcam.c
@@ -1,4 +1,3 @@
-//#include <Python.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <fcntl.h>
@@ -17,8 +16,8 @@
 
 // Default webcam device
 #define VIDEO_DEVICE "/dev/video0"
-#define WIDTH 640
-#define HEIGHT 480
+#define WIDTH 240
+#define HEIGHT 240
 
 // Structure to hold webcam state
 typedef struct {
@@ -34,6 +33,27 @@ static void yuyv_to_grayscale(uint8_t *src, uint8_t *dst, size_t width, size_t h
     }
 }
 
+// Resize 640x480 grayscale to 240x240
+static void resize_640x480_to_240x240(uint8_t *src, uint8_t *dst) {
+    const int src_width = 640;
+    const int src_height = 480;
+    const int dst_width = 240;
+    const int dst_height = 240;
+
+    // Scaling factors
+    float x_ratio = (float)src_width / dst_width;
+    float y_ratio = (float)src_height / dst_height;
+
+    for (int y = 0; y < dst_height; y++) {
+        for (int x = 0; x < dst_width; x++) {
+            // Nearest-neighbor interpolation
+            int src_x = (int)(x * x_ratio);
+            int src_y = (int)(y * y_ratio);
+            dst[y * dst_width + x] = src[src_y * src_width + src_x];
+        }
+    }
+}
+
 // Function to capture a grayscale image
 static mp_obj_t webcam_capture_grayscale(void) {
     webcam_t cam = { .fd = -1, .buffer = NULL, .buffer_length = 0 };
diff --git a/internal_filesystem/apps/com.example.camtest/assets/camtest.py b/internal_filesystem/apps/com.example.camtest/assets/camtest.py
@@ -12,6 +12,7 @@
 image_dsc = None
 image = None
 qr_label = None
+use_webcam = False
 
 
 def print_qr_buffer(buffer):
@@ -92,12 +93,12 @@ def qr_button_click(e):
 
 
 def try_capture():
-    global current_cam_buffer, image_dsc, image
-    if cam.frame_available():
-        # Get new memoryview from camera
+    global current_cam_buffer, image_dsc, image, use_webcam
+    if use_webcam:
+        new_cam_buffer = webcam.capture_grayscale()
+    elif cam.frame_available():
         new_cam_buffer = cam.capture()  # Returns memoryview
-        # Verify buffer size
-        #if len(new_cam_buffer) != width * height * 2:
+    if len(new_cam_buffer):
         #    print("Invalid buffer size:", len(new_cam_buffer))
         #    cam.free_buffer()
         #    return
@@ -107,12 +108,11 @@ def try_capture():
         image.set_src(image_dsc)
         #image.invalidate() #does not work
         # Free the previous buffer (if any) after setting new data
-        if current_cam_buffer is not None:
+        if current_cam_buffer is not None and not use_webcam:
             cam.free_buffer()  # Free the old buffer
         current_cam_buffer = new_cam_buffer  # Store new buffer reference
 
 
-
 def build_ui():
     global image, image_dsc,qr_label
     cont = lv.obj(appscreen)
@@ -195,16 +195,22 @@ def init_cam():
 
 cam = init_cam()
 if not cam:
-    print("init cam failed, retrying...")
-    time.sleep(5)
-    cam = init_cam()
+    print("init cam failed, retrying with webcam...")
+    try:
+        import webcam
+        current_cam_buffer = webcam.capture_grayscale()
+        use_webcam = True
+    except Exception as e:
+        print(f"camtest.py: webcam exception: {e}")
 
-if cam:
+if cam or use_webcam:
     build_ui()
     while appscreen == lv.screen_active() and keepgoing is True:
         try_capture()
         time.sleep_ms(100) # Allow for the MicroPython REPL to still work. Reducing it doesn't seem to affect the on-display FPS.    
     print("App backgrounded, deinitializing camera...")
     cam.deinit()
-    show_launcher()
+else:
+   print("No camera found, exiting...")
 
+show_launcher()
