From 2607559d63fe9c015ebb508c7cb1f70a6b35266a Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Fri, 6 Jul 2018 23:41:01 +0200
Subject: [PATCH] Add some utility functions for working with .flo files.

---
 Makefile             |  8 +++++++-
 eval.cpp             | 29 +++++++++++++++++++++++++++++
 flow.cpp             |  2 +-
 util.cpp             | 26 ++++++++++++++++++++++++++
 flow2rgb.h => util.h | 19 +++++++++++++++----
 vis.cpp              | 36 ++++++++++++++++++++++++++++++++++++
 6 files changed, 114 insertions(+), 6 deletions(-)
 create mode 100644 eval.cpp
 create mode 100644 util.cpp
 rename flow2rgb.h => util.h (81%)
 create mode 100644 vis.cpp

diff --git a/Makefile b/Makefile
index beebb67..609128b 100644
--- a/Makefile
+++ b/Makefile
@@ -25,12 +25,18 @@ OBJS += ffmpeg_raii.o main.o player.o
 %.moc.cpp: %.h
 	moc $< -o $@
 
-all: futatabi
+all: futatabi flow vis eval
 
 mainwindow.o: ui_mainwindow.h
 
 futatabi: $(OBJS) $(CEF_LIBS)
 	$(CXX) -o $@ $^ $(LDFLAGS) $(LDLIBS)
+flow: flow.o
+	$(CXX) -o $@ $^ -lepoxy -lSDL2
+eval: eval.o util.o
+	$(CXX) -o $@ $^
+vis: vis.o util.o
+	$(CXX) -o $@ $^
 
 DEPS=$(OBJS:.o=.d)
 -include $(DEPS)
diff --git a/eval.cpp b/eval.cpp
new file mode 100644
index 0000000..e19ce1f
--- /dev/null
+++ b/eval.cpp
@@ -0,0 +1,29 @@
+// Evaluate a .flo file against ground truth,
+// outputting the average end-point error.
+
+#include <assert.h>
+#include <stdio.h>
+
+#include <memory>
+
+#include "util.h"
+
+using namespace std;
+
+int main(int argc, char **argv)
+{
+	Flow flow = read_flow(argv[1]);
+	Flow gt = read_flow(argv[2]);
+
+	double sum = 0.0;
+	for (unsigned y = 0; y < unsigned(flow.height); ++y) {
+		for (unsigned x = 0; x < unsigned(flow.width); ++x) {
+			float du = flow.flow[y * flow.width + x].du;
+			float dv = flow.flow[y * flow.width + x].dv;
+			float gt_du = gt.flow[y * flow.width + x].du;
+			float gt_dv = gt.flow[y * flow.width + x].dv;
+			sum += hypot(du - gt_du, dv - gt_dv);
+		}
+	}
+	fprintf(stderr, "Average EPE: %.2f pixels\n", sum / (flow.width * flow.height));
+}
diff --git a/flow.cpp b/flow.cpp
index 43daa78..1bac955 100644
--- a/flow.cpp
+++ b/flow.cpp
@@ -16,7 +16,7 @@
 #include <assert.h>
 #include <stdio.h>
 
-#include "flow2rgb.h"
+#include "util.h"
 
 #include <algorithm>
 #include <memory>
diff --git a/util.cpp b/util.cpp
new file mode 100644
index 0000000..3701d62
--- /dev/null
+++ b/util.cpp
@@ -0,0 +1,26 @@
+#include <assert.h>
+#include <stdio.h>
+
+#include <memory>
+
+#include "util.h"
+
+using namespace std;
+
+Flow read_flow(const char *filename)
+{
+	FILE *flowfp = fopen(filename, "rb");
+	uint32_t hdr, width, height;
+	fread(&hdr, sizeof(hdr), 1, flowfp);
+	fread(&width, sizeof(width), 1, flowfp);
+	fread(&height, sizeof(height), 1, flowfp);
+
+	unique_ptr<Vec2[]> flow(new Vec2[width * height]);
+	fread(flow.get(), width * height * sizeof(Vec2), 1, flowfp);
+
+	Flow ret;
+	ret.width = width;
+	ret.height = height;
+	ret.flow = move(flow);
+	return ret;
+}
diff --git a/flow2rgb.h b/util.h
similarity index 81%
rename from flow2rgb.h
rename to util.h
index ca17530..3693fd2 100644
--- a/flow2rgb.h
+++ b/util.h
@@ -1,10 +1,21 @@
-#ifndef _FLOW2RGB_H
-#define _FLOW2RGB_H 1
+#ifndef _UTIL_H
+#define _UTIL_H 1
 
 #include <math.h>
 #include <stdint.h>
-
 #include <algorithm>
+#include <memory>
+
+struct Vec2 {
+	float du, dv;
+};
+
+struct Flow {
+	uint32_t width, height;
+	std::unique_ptr<Vec2[]> flow;
+};
+
+Flow read_flow(const char *filename);
 
 // du and dv are in pixels.
 inline void flow2rgb(float du, float dv, uint8_t *rr, uint8_t *gg, uint8_t *bb)
@@ -42,4 +53,4 @@ inline void flow2rgb(float du, float dv, uint8_t *rr, uint8_t *gg, uint8_t *bb)
 	*bb = lrintf(b * 255.0f);
 }
 
-#endif  // !defined(_FLOW2RGB_H)
+#endif  // !defined(_UTIL_H)
diff --git a/vis.cpp b/vis.cpp
new file mode 100644
index 0000000..8ecf297
--- /dev/null
+++ b/vis.cpp
@@ -0,0 +1,36 @@
+// Visualize a .flo file.
+
+#include <assert.h>
+#include <stdio.h>
+
+#include <memory>
+
+#include "util.h"
+
+using namespace std;
+
+int main(int argc, char **argv)
+{
+	if (argc != 3) {
+		fprintf(stderr, "Usage: ./vis input.flo out.ppm\n");
+		exit(1);
+	}
+
+	Flow flow = read_flow(argv[1]);
+
+	FILE *fp = fopen(argv[2], "wb");
+	fprintf(fp, "P6\n%d %d\n255\n", flow.width, flow.height);
+	for (unsigned y = 0; y < unsigned(flow.height); ++y) {
+		for (unsigned x = 0; x < unsigned(flow.width); ++x) {
+			float du = flow.flow[y * flow.width + x].du;
+			float dv = flow.flow[y * flow.width + x].dv;
+
+			uint8_t r, g, b;
+			flow2rgb(du, dv, &r, &g, &b);
+			putc(r, fp);
+			putc(g, fp);
+			putc(b, fp);
+		}
+	}
+	fclose(fp);
+}
-- 
2.39.2