From faf540b146dc7c4a48480673af9a8de56df2e34f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20W=C3=BChrer?= <def@gmx.at>
Date: Sun, 19 Feb 2017 15:20:12 +0100
Subject: initial commit

---
 piechart.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 piechart.c

diff --git a/piechart.c b/piechart.c
new file mode 100644
index 0000000..aa52afd
--- /dev/null
+++ b/piechart.c
@@ -0,0 +1,92 @@
+/*
+ * BUGS:
+ * adjacient colours could have higher contrast
+ * negative angles 
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <string.h>
+
+const float tau=(float)(M_PI*2);
+
+// draw sector
+void draw(float angle, char* label){
+	const float r=100;
+	static float progress=0;
+	static float overlap=0;
+	float fangle; if(angle<0)fangle=-angle;else fangle=angle-overlap;
+	// Mx,y : move to x,y
+	// Lx,y : draw line to x,y
+	// Arx,ry rot 0,0 x,y : arc with radii rx,ry rotated by rot large-arch or not,clockwise or not to point x,y
+	// z : closes the path
+	float x1=r*cosf(progress);
+	float y1=r*sinf(progress);
+	float x2=r*cosf(progress+fangle);
+	float y2=r*sinf(progress+fangle);
+	float divider=progress+fangle/2;
+	unsigned char rr=(unsigned char)(0xff*((divider)/(tau)));
+	unsigned char gg=(unsigned char)(0xff*((divider-tau/3)/(tau)));
+	unsigned char bb=(unsigned char)(0xff*((divider-2*tau/3)/(tau)));
+	printf("<path stroke=\"#000000\" fill=\"#%02x%02x%02x\" d=\"M250,250 L%f,%f A%f,%f 0 %d,%d %f,%f z\"/>",rr,gg,bb,250+x1,250+y1,r,r,(fangle>M_PI),1,250+x2,250+y2);
+	float xo=250+(3*r/2*cosf(divider));
+	float yo=250+(3*r/2*sinf(divider));
+	printf("<line stroke=\"#000000\" x1=\"%f\" y1=\"%f\" x2=\"%f\" y2=\"%f\" />",250+(2*r/3*cosf(divider)),250+(2*r/3*sinf(divider)),xo,yo);
+	printf("<text x=\"%f\" y=\"%f\">%s</text>\n",xo,yo,label);
+	progress+=fangle;
+	overlap-=angle; // multiple overlaps accumulate
+	if(overlap<0)overlap=0;
+}
+// put preliminary data on the stack
+float scan_line (FILE* input, float sum){
+	char* line=NULL; size_t len=0;
+	if(getline(&line,&len,input) != -1){
+		{ // chomp
+			char* l=&(line[strlen(line)-1]);
+			if(*l=='\n')*l='\0';
+		}
+	/* at the very least, we need a true value.
+	 * everything following it can be label or whatever.
+	 * if strtof does not find anything (or the value is miniscule), the line is obviously a comment and should be ignored.
+	 * (if the value is too huge to handle, the output will be meaningless.)
+	 *
+	 * If the value is negative, it is meant to overlap with the previous record. Or records.
+	 * The value would have to be ignored for computing the sum total.
+	 */
+		char* label=line;
+		float number=strtof(label,&label);
+		if(number>0){
+			sum=scan_line(input,sum+number);
+			float angle=tau*number/sum;
+			draw(angle,label);
+		}else if(number<0){
+			sum=scan_line(input,sum);
+			float angle=tau*number/sum;
+			draw(angle,label);
+		}else{
+			sum=scan_line(input,sum);
+			printf("<!-- %s -->\n",label);
+		}
+	}
+	free(line);
+	return sum;
+}
+
+int main(int argc, char** argv){
+	FILE* input=stdin;
+	// getopts
+	// print boilerplate
+	puts("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n\
+<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1/EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n\
+<svg\n\
+	xmlns=\"http://www.w3.org/2000/svg\"\n\
+	version=\"1.1\"\n\
+	width=\"500\"\n\
+	height=\"500\"\n\
+	viewBox=\"0 0 500 500\"\n\
+>");
+	scan_line(input,0);
+	puts("</svg>");
+	return 0;
+}
-- 
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