Better gradient and filename as param

1 files changed, 15 insertions, 15 deletions

diff --git a/attract.c b/attract.c
index 66fbee4..4526d0e 100644
--- a/attract.c
+++ b/attract.c
@@ -35,16 +35,12 @@ struct colour{
 	unsigned char r,g,b;
 };
 
-__attribute__((unused))
-static struct colour make_colour(int index){
-	static const struct colour clr_base[]={
-		{255,100,100}, {100,255,100}, {100,100,255},
-		{200,200,30}, {200,30,200}, {30,200,200},
-		{100,100,100}, {200,200,200}
-	};
-	static const int nbase=sizeof(clr_base)/sizeof(clr_base[0]);
-
-	return clr_base[index%nbase];
+static struct colour make_colour(double complex z){
+	static const double N=3;
+	double norm=cabs(z);
+	if(norm>N)norm=N;
+	int clrv=(int)(norm/N*255);
+	return (struct colour){clrv,clrv,clrv};
 }
 
 struct config{
@@ -108,8 +104,7 @@ static void* thread_entry(void *arg_vp){
 				// struct colour clr=make_colour(bi);
 			}
 
-			unsigned char clrv=(int)(cabs(z)/3*255)%256;
-			struct colour clr={clrv,clrv,clrv};
+			struct colour clr=make_colour(z);
 			img[3*(iy*cfg.width+ix)+0]=clr.r;
 			img[3*(iy*cfg.width+ix)+1]=clr.g;
 			img[3*(iy*cfg.width+ix)+2]=clr.b;
@@ -126,10 +121,15 @@ int main(int argc,char **argv){
 		.exponent=8.5
 	};
 
-	assert(argc==1||argc==2);
-	if(argc==2){
+	if(argc>=2){
 		cfg.exponent=strtod(argv[1],NULL);
 	}
+	const char *fname;
+	if(argc>=3){
+		fname=argv[2];
+	} else {
+		fname="out.png";
+	}
 
 	unsigned char img[cfg.width*cfg.height*3];
 
@@ -169,5 +169,5 @@ int main(int argc,char **argv){
 		}
 	}
 
-	lodepng_encode_file("out.png",img,cfg.width,cfg.height,LCT_RGB,8);
+	lodepng_encode_file(fname,img,cfg.width,cfg.height,LCT_RGB,8);
 }