quirc-demo-opencv: Add OpenCV version of the demo

My motivation is to experiment quirc on macOS, where
neither of SDL1 or V4L2 work.

```
% brew install opencv
% brew install pkg-config
% brew install bsdmake
% bsdmake quirc-demo-opencv
% ./quirc-demo-opencv
```

Note: the macOS version of GNU make (/usr/bin/make) is a bit old
for quirc's Makefile.

Makefile

@@ -30,10 +30,15 @@ LIB_OBJ = \
 DEMO_OBJ = \
     demo/camera.o \
     demo/mjpeg.o \
-    demo/convert.o \
+    demo/convert.o
+DEMO_UTIL_OBJ = \
     demo/dthash.o \
     demo/demoutil.o
 
+OPENCV_CFLAGS != pkg-config --cflags opencv4
+OPENCV_LIBS != pkg-config --libs opencv4
+QUIRC_CXXFLAGS = $(QUIRC_CFLAGS) $(OPENCV_CFLAGS) --std=c++17
+
 all: libquirc.so qrtest inspect quirc-demo quirc-scanner
 
 qrtest: tests/dbgutil.o tests/qrtest.o libquirc.a
@@ -42,11 +47,14 @@ qrtest: tests/dbgutil.o tests/qrtest.o libquirc.a
 inspect: tests/dbgutil.o tests/inspect.o libquirc.a
 	$(CC) -o $@ tests/dbgutil.o tests/inspect.o libquirc.a $(LDFLAGS) -lm -ljpeg -lpng $(SDL_LIBS) -lSDL_gfx
 
-quirc-demo: $(DEMO_OBJ) demo/demo.o libquirc.a
+quirc-demo: $(DEMO_OBJ) $(DEMO_UTIL_OBJ) demo/demo.o libquirc.a
-	$(CC) -o $@ $(DEMO_OBJ) demo/demo.o libquirc.a $(LDFLAGS) -lm -ljpeg $(SDL_LIBS) -lSDL_gfx
+	$(CC) -o $@ $(DEMO_OBJ) $(DEMO_UTIL_OBJ) demo/demo.o libquirc.a $(LDFLAGS) -lm -ljpeg $(SDL_LIBS) -lSDL_gfx
 
-quirc-scanner: $(DEMO_OBJ) demo/scanner.o libquirc.a
+quirc-demo-opencv: $(DEMO_UTIL_OBJ) demo/demo_opencv.o libquirc.a
-	$(CC) -o $@ $(DEMO_OBJ) demo/scanner.o libquirc.a $(LDFLAGS) -lm -ljpeg
+	$(CXX) -o $@ $(DEMO_UTIL_OBJ) demo/demo_opencv.o libquirc.a $(LDFLAGS) -lm -ljpeg $(OPENCV_LIBS)
+
+quirc-scanner: $(DEMO_OBJ) $(DEMO_UTIL_OBJ) demo/scanner.o libquirc.a
+	$(CC) -o $@ $(DEMO_OBJ) $(DEMO_UTIL_OBJ) demo/scanner.o libquirc.a $(LDFLAGS) -lm -ljpeg
 
 libquirc.a: $(LIB_OBJ)
 	rm -f $@
@@ -62,12 +70,17 @@ libquirc.so.$(LIB_VERSION): $(LIB_OBJ)
 .c.o:
 	$(CC) $(QUIRC_CFLAGS) -o $@ -c $<
 
+.SUFFIXES: .cxx
+.cxx.o:
+	$(CXX) $(QUIRC_CXXFLAGS) -o $@ -c $<
+
 install: libquirc.a libquirc.so.$(LIB_VERSION) quirc-demo quirc-scanner
 	install -o root -g root -m 0644 lib/quirc.h $(DESTDIR)$(PREFIX)/include
 	install -o root -g root -m 0644 libquirc.a $(DESTDIR)$(PREFIX)/lib
 	install -o root -g root -m 0755 libquirc.so.$(LIB_VERSION) \
 		$(DESTDIR)$(PREFIX)/lib
 	install -o root -g root -m 0755 quirc-demo $(DESTDIR)$(PREFIX)/bin
+	# install -o root -g root -m 0755 quirc-demo-opencv $(DESTDIR)$(PREFIX)/bin
 	install -o root -g root -m 0755 quirc-scanner $(DESTDIR)$(PREFIX)/bin
 
 uninstall:
@@ -75,6 +88,7 @@ uninstall:
 	rm -f $(DESTDIR)$(PREFIX)/lib/libquirc.so.$(LIB_VERSION)
 	rm -f $(DESTDIR)$(PREFIX)/lib/libquirc.a
 	rm -f $(DESTDIR)$(PREFIX)/bin/quirc-demo
+	rm -f $(DESTDIR)$(PREFIX)/bin/quirc-demo-opencv
 	rm -f $(DESTDIR)$(PREFIX)/bin/quirc-scanner
 
 clean:
@@ -85,4 +99,5 @@ clean:
 	rm -f qrtest
 	rm -f inspect
 	rm -f quirc-demo
+	rm -f quirc-demo-opencv
 	rm -f quirc-scanner

demo/demo_opencv.cxx

@@ -0,0 +1,263 @@
+/* quirc -- QR-code recognition library
+ * Copyright (C) 2010-2012 Daniel Beer <dlbeer@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <unistd.h>
+#include <quirc.h>
+#include <time.h>
+#include <getopt.h>
+
+#include <opencv2/videoio.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+
+using namespace cv;
+
+#include "camera.h"
+#include "convert.h"
+#include "dthash.h"
+#include "demoutil.h"
+
+/* Collected command-line arguments */
+static int want_frame_rate = 0;
+static int want_verbose = 0;
+static int printer_timeout = 2;
+
+static const int font = FONT_HERSHEY_PLAIN;
+static const int thickness = 2;
+static const double font_scale = 1.5;
+static Scalar blue = Scalar(255, 0, 8);
+
+static void fat_text(Mat &screen, int x, int y, const char *text)
+{
+	putText(screen, text, Point(x, y), font, font_scale, blue, thickness);
+}
+
+static void fat_text_cent(Mat &screen, int x, int y, const char *text)
+{
+	int baseline;
+
+	Size size = getTextSize(text, font, font_scale, thickness, &baseline);
+	putText(screen, text, Point(x - size.width / 2, y - size.height /2),
+		font, font_scale, blue, thickness);
+}
+
+static void draw_qr(Mat &screen, struct quirc *q, struct dthash *dt)
+{
+	int count = quirc_count(q);
+	int i;
+
+	for (i = 0; i < count; i++) {
+		struct quirc_code code;
+		struct quirc_data data;
+		quirc_decode_error_t err;
+		int j;
+		int xc = 0;
+		int yc = 0;
+		char buf[128];
+
+		quirc_extract(q, i, &code);
+
+		for (j = 0; j < 4; j++) {
+			struct quirc_point *a = &code.corners[j];
+			struct quirc_point *b = &code.corners[(j + 1) % 4];
+
+			xc += a->x;
+			yc += a->y;
+			line(screen, Point(a->x, a->y), Point(b->x, b->y), blue, 8);
+		}
+
+		xc /= 4;
+		yc /= 4;
+
+		if (want_verbose) {
+			snprintf(buf, sizeof(buf), "Code size: %d cells",
+				 code.size);
+			fat_text_cent(screen, xc, yc - 20, buf);
+		}
+
+		err = quirc_decode(&code, &data);
+
+		if (err) {
+			if (want_verbose)
+				fat_text_cent(screen, xc, yc, quirc_strerror(err));
+		} else {
+			fat_text_cent(screen, xc, yc, (const char *)data.payload);
+			print_data(&data, dt, want_verbose);
+
+			if (want_verbose) {
+				snprintf(buf, sizeof(buf),
+					 "Ver: %d, ECC: %c, Mask: %d, Type: %d",
+					 data.version, "MLHQ"[data.ecc_level],
+					 data.mask, data.data_type);
+				fat_text_cent(screen, xc, yc + 20, buf);
+			}
+		}
+	}
+}
+
+static int main_loop(VideoCapture &cap, struct quirc *q)
+{
+	time_t last_rate = 0;
+	int frame_count = 0;
+	char rate_text[64];
+	struct dthash dt;
+
+	rate_text[0] = 0;
+	dthash_init(&dt, printer_timeout);
+
+	Mat frame;
+	for (;;) {
+		time_t now = time(NULL);
+
+		cap.read(frame);
+		if (frame.empty()) {
+			perror("empty frame");
+			return 0;
+		}
+
+		int w;
+		int h;
+		uint8_t *buf = quirc_begin(q, &w, &h);
+
+		/* convert frame into buf */
+		assert(frame.cols == w);
+		assert(frame.rows == h);
+		Mat gray;
+		cvtColor(frame, gray, COLOR_BGR2GRAY, 0);
+		for (int y = 0; y < gray.rows; y++) {
+			for (int x = 0; x < gray.cols; x++) {
+				buf[(y * w + x)] = gray.at<uint8_t>(y, x);
+			}
+		}
+
+		quirc_end(q);
+
+		draw_qr(frame, q, &dt);
+		if (want_frame_rate)
+			fat_text(frame, 20, 20, rate_text);
+
+		imshow("quirc-demo-opencv", frame);
+		waitKey(5);
+
+		if (now != last_rate) {
+			snprintf(rate_text, sizeof(rate_text),
+				 "Frame rate: %d fps", frame_count);
+			frame_count = 0;
+			last_rate = now;
+		}
+
+		frame_count++;
+	}
+}
+
+static int run_demo(void)
+{
+	struct quirc *qr;
+	VideoCapture cap(0);
+	unsigned int width;
+	unsigned int height;
+
+	if (!cap.isOpened()) {
+		perror("camera_open");
+		goto fail_qr;
+	}
+
+	width = cap.get(CAP_PROP_FRAME_WIDTH);
+	height = cap.get(CAP_PROP_FRAME_HEIGHT);
+
+	qr = quirc_new();
+	if (!qr) {
+		perror("couldn't allocate QR decoder");
+		goto fail_qr;
+	}
+
+	if (quirc_resize(qr, width, height) < 0) {
+		perror("couldn't allocate QR buffer");
+		goto fail_qr_resize;
+	}
+
+	if (main_loop(cap, qr) < 0) {
+		goto fail_main_loop;
+	}
+
+	quirc_destroy(qr);
+
+	return 0;
+
+fail_main_loop:
+fail_qr_resize:
+	quirc_destroy(qr);
+fail_qr:
+
+	return -1;
+}
+
+static void usage(const char *progname)
+{
+	printf("Usage: %s [options]\n\n"
+"Valid options are:\n\n"
+"    -f             Show frame rate on screen.\n"
+"    -v             Show extra data for detected codes.\n"
+"    -p <timeout>   Set printer timeout (seconds).\n"
+"    --help         Show this information.\n"
+"    --version      Show library version information.\n",
+	progname);
+}
+
+int main(int argc, char **argv)
+{
+	static const struct option longopts[] = {
+		{"help",		0, 0, 'H'},
+		{"version",		0, 0, 'V'},
+		{NULL,			0, 0, 0}
+	};
+	int opt;
+
+	printf("quirc demo with OpenCV\n");
+	printf("Copyright (C) 2010-2014 Daniel Beer <dlbeer@gmail.com>\n");
+	printf("\n");
+
+	while ((opt = getopt_long(argc, argv, "fvg:p:",
+				  longopts, NULL)) >= 0)
+		switch (opt) {
+		case 'V':
+			printf("Library version: %s\n", quirc_version());
+			return 0;
+
+		case 'H':
+			usage(argv[0]);
+			return 0;
+
+		case 'v':
+			want_verbose = 1;
+			break;
+
+		case 'f':
+			want_frame_rate = 1;
+			break;
+
+		case 'p':
+			printer_timeout = atoi(optarg);
+			break;
+
+		case '?':
+			fprintf(stderr, "Try --help for usage information\n");
+			return -1;
+		}
+
+	return run_demo();
+}

demo/demoutil.h

@@ -20,6 +20,10 @@
 #include "dthash.h"
 #include "quirc.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Check if we've seen the given code, and if not, print it on stdout.
  * Include version info if requested.
  */
@@ -31,4 +35,8 @@ void print_data(const struct quirc_data *data, struct dthash *dt,
  */
 int parse_size(const char *text, int *video_width, int *video_height);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif

demo/dthash.h

@@ -40,6 +40,10 @@ struct dthash {
 	int			timeout;
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Initialise a detector hash with the given timeout. */
 void dthash_init(struct dthash *d, int timeout);
 
@@ -50,4 +54,8 @@ void dthash_init(struct dthash *d, int timeout);
  */
 int dthash_seen(struct dthash *d, const struct quirc_data *data);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif