util: Add sobel operator

2 files changed, 45 insertions, 0 deletions

diff --git a/src/util.c b/src/util.c
index ddd46d3..ddb3ce9 100644
--- a/src/util.c
+++ b/src/util.c
@@ -136,3 +136,45 @@ print_time(int64_t msec) {
 
 	printf("%02d:%02d:%02d.%03jd", hh, mm, ss, msec);
 }
+
+int
+sobel(struct video_frame *frame, unsigned char **d)
+{
+	unsigned char *data;
+	unsigned char *p = frame->data;
+	int x,y;
+	int Yx, Yy, Y;
+
+	data = malloc(frame->width * frame->height);
+	if (data == NULL)
+		return -1;
+
+	for (y = 1; y < frame->height-1; ++y) {
+		for (x = 1; x < frame->width-1; ++x) {
+			Yx = (+1 * p[(y-1) * frame->stride + (x-1)]
+			      -1 * p[(y-1) * frame->stride + (x+1)]
+			      +2 * p[(y  ) * frame->stride + (x-1)]
+			      -2 * p[(y  ) * frame->stride + (x+1)]
+			      +1 * p[(y+1) * frame->stride + (x-1)]
+			      -1 * p[(y+1) * frame->stride + (x+1)]);
+			Yx = abs(Yx);
+
+			Yy = (+1 * p[(y-1) * frame->stride + (x-1)]
+			      +2 * p[(y-1) * frame->stride + (x  )]
+			      +1 * p[(y-1) * frame->stride + (x+1)]
+			      -1 * p[(y+1) * frame->stride + (x-1)]
+			      -2 * p[(y+1) * frame->stride + (x  )]
+			      -1 * p[(y+1) * frame->stride + (x+1)]);
+			Yy = abs(Yy);
+
+			Y = (Yx > Yy ? Yx : Yy) / 4;
+			if (Y > 255) Y = 255;
+			
+			data[y * frame->width + x] = Y;
+		}
+	}
+
+	*d = data;
+
+	return 0;
+}
diff --git a/src/util.h b/src/util.h
index 4666b06..22d5587 100644
--- a/src/util.h
+++ b/src/util.h
@@ -32,4 +32,7 @@ frame_average(struct video_frame *frame);
 void
 print_time(int64_t msec);
 
+int
+sobel(struct video_frame *frame, unsigned char **d);
+
 #endif /* _UTIL_H_ */