Almost ready image view OpenGL module

Bresenham_circle.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *drawCircle(int R, int geom){
+	if(R > 200 || R < 1) return NULL;
+	int S, i, Y = 2 * R + 2;
+	if(geom)
+		S = Y * (R + 1);
+	else
+		S = Y * (Y - 1);
+	char *buf = malloc(S+1);
+	if(!buf) return NULL;
+	memset(buf, ' ', S);
+	buf[S] = 0;
+	for(i = Y-1; i < S; i+=Y) buf[i] = '\n';
+	inline void DrawPixel(int x, int y){
+		if(geom){
+			if(y%2==0) buf[Y * y/2 + x] = '*';
+		}else{
+			buf[Y * y + x] = '*';
+		}
+	}
+	// Bresenham's circle algorithm
+	int x = R;
+	int y = 0;
+	int radiusError = 1-x;
+	while(x >= y){
+		DrawPixel(x + R,   y + R);
+		DrawPixel(y + R,   x + R);
+		DrawPixel(-x + R,  y + R);
+		DrawPixel(-y + R,  x + R);
+		DrawPixel(-x + R, -y + R);
+		DrawPixel(-y + R, -x + R);
+		DrawPixel(x + R,  -y + R);
+		DrawPixel(y + R,  -x + R);
+		y++;
+		if (radiusError < 0){
+			radiusError += 2 * y + 1;
+		}else{
+			x--;
+			radiusError += 2 * (y - x) + 1;
+		}
+	}
+	return buf;
+}
+
+int main(int argc, char **argv){
+	int i, R;
+	char *buf;
+	for(i = 1; i < argc; i++){
+		if(!(buf = drawCircle(R = atoi(argv[i]), 1))){
+			printf("Wrong parameter %s\n", argv[i]);
+			continue;
+		}
+		printf("\nCircle with R = %d:\n%s\n", R, buf);
+		free(buf); buf = NULL;
+	}
+	return 0;
+}