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webcam: keep aspect ratio

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This commit is contained in:
Thomas Farstrike
2025-05-14 14:22:18 +02:00
parent 9b6a197e17
commit e796830334
1 changed files with 13 additions and 6 deletions
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c_mpos/src/webcam.c
+13 -6
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@@ -31,15 +31,22 @@ typedef struct _webcam_obj_t {
} webcam_obj_t;
static void yuyv_to_grayscale_240x240(unsigned char *yuyv, unsigned char *gray, int in_width, int in_height) {
float x_ratio = (float)in_width / OUTPUT_WIDTH;
float y_ratio = (float)in_height / OUTPUT_HEIGHT;
// Crop to 480x480 centered region
int crop_size = 480;
int crop_x_offset = (in_width - crop_size) / 2; // Center the crop: (640 - 480) / 2 = 80
int crop_y_offset = (in_height - crop_size) / 2; // Center the crop: (480 - 480) / 2 = 0
// Downscale ratios from 480x480 to 240x240
float x_ratio = (float)crop_size / OUTPUT_WIDTH; // 480 / 240 = 2.0
float y_ratio = (float)crop_size / OUTPUT_HEIGHT; // 480 / 240 = 2.0
for (int y = 0; y < OUTPUT_HEIGHT; y++) {
for (int x = 0; x < OUTPUT_WIDTH; x++) {
int src_x = (int)(x * x_ratio);
int src_y = (int)(y * y_ratio);
int src_index = (src_y * in_width + src_x) * 2;
gray[y * OUTPUT_WIDTH + x] = yuyv[src_index];
// Map output pixel to cropped region
int src_x = (int)(x * x_ratio) + crop_x_offset; // Adjust for crop offset
int src_y = (int)(y * y_ratio) + crop_y_offset; // Adjust for crop offset
int src_index = (src_y * in_width + src_x) * 2; // YUYV uses 2 bytes per pixel
gray[y * OUTPUT_WIDTH + x] = yuyv[src_index]; // Extract Y channel
}
}
}