shithub: ifilter

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add color inversion filter

--- a/README

+++ b/README

@@ -8,6 +8,7 @@

 Available color filters are:

 - grayscale

 - sepia

+- invert

-usage: ifilter [grayscale|sepia]

+usage: ifilter [grayscale|sepia|invert]

--- a/ifilter.c

+++ b/ifilter.c

@@ -5,8 +5,14 @@

 #define MIN(x,y) ((x)<(y)?(x):(y))

-typedef void(*filterfun)(uchar[3]);

+typedef struct Filter Filter;

+struct Filter

+{

+	const char *name;

+	void (*filter)(uchar[3]);

+};

+

 void

 grayscale(uchar p[3])

 {

@@ -28,12 +34,26 @@

 }

 void

+invert(uchar p[3])

+{

+	p[0] = 255 - p[0];

+	p[1] = 255 - p[1];

+	p[2] = 255 - p[2];

+}

+

+void

 usage(void)

 {

-	fprint(2, "usage: %s [grayscale|sepia]\n", argv0);

+	fprint(2, "usage: %s [grayscale|sepia|invert]\n", argv0);

 	exits("usage");

 }

+static Filter filters[] = {

+	{ "grayscale", grayscale },

+	{ "sepia", sepia },

+	{ "invert", invert },

+};

+

 void

 main(int argc, char *argv[])

 {

@@ -40,18 +60,20 @@

 	Memimage *i;

 	int w, h, p, n;

 	uchar *buf;

-	filterfun filter;

+	Filter *f;

-	filter = nil;

+	f = nil;

 	ARGBEGIN{

 	}ARGEND;

 	if(argc!=1)

 		usage();

-	if(strcmp(*argv, "grayscale")==0)

-		filter = grayscale;

-	else if(strcmp(*argv, "sepia")==0)

-		filter = sepia;

-	else

+	for(n=0; n<nelem(filters); n++){

+		if(strcmp(*argv, filters[n].name)==0){

+			f = filters+n;

+			break;

+		}

+	}

+	if(f==nil)

 		usage();

 	if(memimageinit()<0)

 		sysfatal("memimageinit: %r");

@@ -66,9 +88,8 @@

 		sysfatal("malloc: %r");

 	if(unloadmemimage(i, i->r, buf, n)<0)

 		sysfatal("unloadmemimage: %r");

-	for(p = 0; p < n; p+=4){

-		filter(buf+p);

-	}

+	for(p = 0; p < n; p+=4)

+		f->filter(buf+p);

 	if(loadmemimage(i, i->r, buf, n)<0)

 		sysfatal("unloadmemimage: %r");

 	writememimage(1, i);