From dae78c4c915d420cfb45d5e0797c130eeba41b4b Mon Sep 17 00:00:00 2001
From: John Tsiombikas <jtsiomb@census.gr>
Date: Thu, 12 Sep 2019 15:21:45 +0300
Subject: [PATCH] capture feature

---
 src/app.c       |    6 ++++++
 src/app.h       |    1 +
 src/main_glut.c |   57 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/src/app.c b/src/app.c
index 8c4b6dd..7f6ed9f 100644
--- a/src/app.c
+++ b/src/app.c
@@ -48,6 +48,12 @@ void app_display(void)
 	glLineWidth(5.0);
 
 	anim = fmod(t / 6.0f, LOOPTIME);
+
+	if(nloops > 0 && (anim < t / 6.0f)) {
+		app_quit();
+		return;
+	}
+
 	alpha = 1.0f - ((anim - (LOOPTIME - 0.075)) / 0.06f);
 	if(alpha < 0.0f) alpha = 0.0f;
 	if(alpha > 1.0f) alpha = 1.0f;
diff --git a/src/app.h b/src/app.h
index 70f89ed..b93c6b7 100644
--- a/src/app.h
+++ b/src/app.h
@@ -9,6 +9,7 @@ int nverts;
 int msaa;
 int fullscr;
 long msec;
+int nloops;
 
 int app_init(void);
 void app_display(void);
diff --git a/src/main_glut.c b/src/main_glut.c
index 2cd51ef..73cab31 100644
--- a/src/main_glut.c
+++ b/src/main_glut.c
@@ -1,3 +1,4 @@
+#include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
 #include <GL/glut.h>
@@ -7,13 +8,19 @@ static void display(void);
 static void idle(void);
 static void reshape(int x, int y);
 static void keyb(unsigned char key, int x, int y);
+static int save_image(const char *fname, unsigned char *pix, int xsz, int ysz);
 
 static long start_time;
+static int capture;
+static long cap_frame_interval = 67;
+static unsigned char *pixels;
 
 int main(int argc, char **argv)
 {
+	char *env;
 	unsigned int flags = GLUT_RGB | GLUT_DOUBLE;
 
+	glutInitWindowSize(1280, 800);
 	glutInit(&argc, argv);
 	if(app_parse_args(argc, argv) == -1) {
 		return 1;
@@ -25,10 +32,12 @@ int main(int argc, char **argv)
 	}
 #endif
 
-	glutInitWindowSize(1280, 800);
 	glutInitDisplayMode(flags);
 	glutCreateWindow("census");
 
+	win_width = glutGet(GLUT_WINDOW_WIDTH);
+	win_height = glutGet(GLUT_WINDOW_HEIGHT);
+
 	if(fullscr) {
 		glutFullScreen();
 		glutSetCursor(GLUT_CURSOR_NONE);
@@ -39,6 +48,16 @@ int main(int argc, char **argv)
 	glutReshapeFunc(reshape);
 	glutKeyboardFunc(keyb);
 
+	if((env = getenv("CAPFPS")) && (cap_frame_interval = atoi(env)) > 0) {
+		cap_frame_interval = 1000 / cap_frame_interval;
+		capture = 1;
+		if(!(pixels = malloc(win_width * win_height * 3))) {
+			fprintf(stderr, "failed to allocate frame capture buffer\n");
+			return 1;
+		}
+		nloops = 1;
+	}
+
 	if(app_init() == -1) {
 		return 1;
 	}
@@ -50,10 +69,24 @@ int main(int argc, char **argv)
 
 static void display(void)
 {
-	msec = glutGet(GLUT_ELAPSED_TIME) - start_time;
+	if(capture) {
+		msec += cap_frame_interval;
+	} else {
+		msec = glutGet(GLUT_ELAPSED_TIME) - start_time;
+	}
 
 	app_display();
 
+	if(capture) {
+		static int frame;
+		char buf[64];
+
+		glReadPixels(0, 0, win_width, win_height, GL_RGB, GL_UNSIGNED_BYTE, pixels);
+
+		sprintf(buf, "frm%03d.ppm", frame++);
+		save_image(buf, pixels, win_width, win_height);
+	}
+
 	glutSwapBuffers();
 	assert(glGetError() == GL_NO_ERROR);
 }
@@ -95,3 +128,23 @@ void app_windowed(void)
 	glutReshapeWindow(saved_width, saved_height);
 	glutSetCursor(GLUT_CURSOR_INHERIT);
 }
+
+static int save_image(const char *fname, unsigned char *pix, int xsz, int ysz)
+{
+	int i;
+	FILE *fp;
+
+	if(!(fp = fopen(fname, "wb"))) {
+		fprintf(stderr, "failed to open %s for writing\n", fname);
+		return -1;
+	}
+	fprintf(fp, "P6\n%d %d\n255\n", xsz, ysz);
+
+	for(i=0; i<xsz * ysz; i++) {
+		fputc(*pix++, fp);
+		fputc(*pix++, fp);
+		fputc(*pix++, fp);
+	}
+	fclose(fp);
+	return 0;
+}
-- 
1.7.10.4