first attempt to measure the level

getvideo.c

@@ -91,6 +91,8 @@ Video *vid_open(char *name) {
 		}
 	}
 
+	vid_getctrls(video);
+
 	return video;
 }
 
@@ -324,3 +326,32 @@ int vid_stop(Video* video) {
 	return 0;
 };
 
+
+void vid_getctrls (Video* video) {
+	int i, j;
+	struct v4l2_queryctrl queryctrl;
+	memset (&queryctrl, 0, sizeof (queryctrl));
+	for (j = 0, i = V4L2_CID_BASE; i < V4L2_CID_DETECT_CLASS_BASE+0x1000; i++) {
+		queryctrl.id  = i;
+        if (0 == ioctl (video->fd, VIDIOC_QUERYCTRL, &queryctrl)) {
+        	if (j == 0) video->ctrl_bright = queryctrl.id;
+        	else if (j == 1) video->ctrl_contrast = queryctrl.id;
+        	j++;
+        }
+	}
+};
+
+
+void vid_setctrls (Video* video, int bright, int contrast) {
+	struct v4l2_control ctrl;
+
+	CLEAR(ctrl);
+	ctrl.id = video->ctrl_bright;
+	ctrl.value = bright;
+	xioctl (video->fd, VIDIOC_S_CTRL, &ctrl);
+
+	CLEAR(ctrl);
+	ctrl.id = video->ctrl_contrast;
+	ctrl.value = contrast;
+	xioctl (video->fd, VIDIOC_S_CTRL, &ctrl);
+};

image.c

@@ -135,6 +135,28 @@ void image_draw_rect (ImageRaw *img, Rect *r, int col) {
 }
 
 
+void image_get_minmax (ImageRaw *img, Rect *r, int *min, int *max) {
+	int x, y, l, cr, cg, cb;
+	if (img == NULL || img->data == NULL) return;
+
+	cr = (unsigned char)*(img->data+0+3*(r->x+r->y*img->w));
+	cg = (unsigned char)*(img->data+1+3*(r->x+r->y*img->w));
+	cb = (unsigned char)*(img->data+2+3*(r->x+r->y*img->w));
+	*min = *max = cr + cg + cb;
+
+	for (x = r->x; x < (r->x+r->w) && x < img->w; x++)
+		for (y = r->y; y < (r->w + r->h) && y < img->h; y++) {
+			cr = (unsigned char)*(img->data+0+3*(x+y*img->w));
+			cg = (unsigned char)*(img->data+1+3*(x+y*img->w));
+			cb = (unsigned char)*(img->data+2+3*(x+y*img->w));
+//			printf ("%d %d %d\n", cr, cg, cb);
+			l = cr + cg + cb;
+			if (l < *min) *min = l;
+			if (l > *max) *max = l;
+		}
+}
+
+
 
 ImageFloat *imageF_alloc (int w, int h) {
 	ImageFloat *i = NULL;

main.c

@@ -14,6 +14,8 @@ int conf_samples = 25;
 int conf_rotate = 0;
 Rect conf_rect = { .x = 315, .y = 0, .w = 70, .h = 1910 };
 
+int detect_level(ImageFloat *imgf);
+
 /*
  * open video device
  * read multiple images into memory
@@ -45,7 +47,7 @@ int main(int argc, char **argv) {
 	char outdate[LEN_FILENAME];
 	time_t curtime = time(NULL);
 	struct tm *curtime_tm = NULL;
-	int i;
+	int i, c, b, level, cont, bright, min, max;
 
 	// for debugging only
 	curtime_tm = localtime(&curtime);
@@ -92,9 +94,38 @@ int main(int argc, char **argv) {
 //	printf ("vidoiltank\n");
 //	printf ("  device: %s (%d x %d)\n", conf_devname, conf_width, conf_height);
 
+	//
+	// open video device
 	if ((video = vid_open("/dev/video0")) == NULL) return -1;
 	if (vid_start(video, conf_iomode, conf_width, conf_height) == -1) return -1;
 
+	//
+	// search for god brightness and contrast
+	printf ("check controls\n");
+	cont = 200;		// just picked some random numbers
+	bright = 170;	// just picked some random numbers
+	for (level = 0, c = 32; c <= 250; c += 64)
+		for (b = 32; b <= 250; b += 64) {
+			vid_setctrls(video, b, c);
+			do {} while ((tmpimg = vid_grabimage(video, img)) == NULL && errno == EAGAIN);
+			if (tmpimg == NULL) {
+				printf ("could not grab image\n");
+				exit(1);
+			}
+			img = tmpimg;
+			image_get_minmax (img, &conf_rect, &min, &max);
+			if (max-min > level) {
+				cont = c;
+				bright = b;
+				level = max-min;
+			}
+		}
+	printf ("found best control: contrast: %d   brightness: %d\n", cont, bright);
+	vid_setctrls(video, bright, cont);
+
+	//
+	// get samples
+	printf ("Read Samples\n");
 	for (i = 0; i < conf_samples; i++) {
 		do {} while ((tmpimg = vid_grabimage(video, img)) == NULL && errno == EAGAIN);
 		if (tmpimg == NULL) {
@@ -110,7 +141,7 @@ int main(int argc, char **argv) {
 		}
 
 		if (i == 0) {
-			snprintf (fn, 3*LEN_FILENAME, "%s/%s-img-%02d.jpg", conf_debugout, outdate, i);
+			snprintf (fn, 3*LEN_FILENAME, "%s/%s-img-%02d-%02d.jpg", conf_debugout, outdate, bright, cont);
 			image_draw_rect(img, &conf_rect, 0x00FFFF);
 			image_save(img, fn, 98);
 		}
@@ -123,8 +154,63 @@ int main(int argc, char **argv) {
 	snprintf (fn, 3*LEN_FILENAME, "%s/%s-imgf-%03d.jpg", conf_debugout, outdate, conf_samples);
 	image_save(tmpimg, fn, 98);
 
+	level = detect_level(imgf);
+	tmpimg = image_copyF(imgf);
+	Rect r = {.x = 0,  .y = level, .w = 10, .h = 1};
+	image_draw_rect(tmpimg,  &r, 0x0000FF00);
+	snprintf (fn, 3*LEN_FILENAME, "%s/%s-img-data.jpg", conf_debugout, outdate);
+	image_save(tmpimg, fn, 98);
+
+	printf ("%s Found Level: %5.2f    Y-Pos: %d\n", outdate, 100.0 * (1.0-(float)level/(float)imgf->h), level);
+
 	return 0;
+};
+
+
+int detect_level(ImageFloat *imgf) {
+	int y, x, ylow, level;
+	float v = 0.0, vmin, vmax;
+
+	//
+	// calculate average, and save value in left row
+	for (y = 0; y < imgf->h; y++) {
+		for (v = 0.0, x = 0; x < imgf->w; x++)
+			v += imgf->data[x + y * imgf->w];
+		v = v / (float) x;
+		if (y == 0) vmin = vmax = v;
+		if (vmin > v) vmin = v;
+		if (vmax < v) vmax = v;
+
+		// save result in the top left position,
+		// together with a bar for display
+		imgf->data[y * imgf->w] = v;
 	}
 
+	//
+	// normalize 0.0 .. 1.0
+	for (y = 0; y < imgf->h; y++) for (x = 0; x < imgf->w; x++) {
+		imgf->data[x + y * imgf->w] = (imgf->data[x + y * imgf->w]-vmin)/(vmax-vmin);
+	}
+
+	//
+	// search for the level from below
+	vmin = 1.0;
+	vmax = 0.0;
+	int avg = 8;
+
+	level = 0;
+	for (ylow = 0; ylow < imgf->h; ylow++) {
+		if (ylow == 0) v = imgf->data[(ylow) * imgf->w];
+		v = ((float)avg-1.0) * v/(float)avg + imgf->data[(ylow) * imgf->w]/(float) avg;
+		for (x = 0; x < 8; x++) imgf->data[x + (ylow) * imgf->w] = v;
+	}
+	for (ylow = imgf->h - 1; ylow >= 0; ylow--) {
+		if (ylow == imgf->h - 1) v = imgf->data[(ylow) * imgf->w];
+		v = ((float)avg-1.0) * v/(float)avg + imgf->data[(ylow) * imgf->w]/(float) avg;
+		for (x = 4; x < 16; x++) imgf->data[x + (ylow) * imgf->w] = v;
+		if (v < 0.1) level = ylow;
+	}
 
+	return level;
+};
 

vidoiltank.h

@@ -74,6 +74,9 @@ struct s_video {
 	struct v4l2_crop crop;
 	struct v4l2_format fmt;
 
+	unsigned int ctrl_bright;
+	unsigned int ctrl_contrast;
+
 } typedef Video;
 
 
@@ -104,6 +107,7 @@ ImageFloat *imageF_alloc (int w, int h);
 ImageFloat *imageF_copy(ImageRaw *iraw, Rect *r);
 ImageRaw *image_copyF(ImageFloat *ifloat);
 void imageF_add(ImageFloat *ifloat, ImageRaw *iraw, Rect *r);
+void image_get_minmax (ImageRaw *img, Rect *r, int *min, int *max);
 
 /* getvideo.c
  *
@@ -115,6 +119,7 @@ int vid_start(Video* video, int ionmode, int width, int height);
 ImageRaw *vid_grabimage(Video* video, ImageRaw *img);
 int vid_stop(Video* video);
 void vid_close(Video* video);
-
+void vid_getctrls (Video* video);
+void vid_setctrls (Video* video, int bright, int contrast);
 
 #endif