ref: 19d022a35e52dcfcb999bf53db7e9e171d1f2176
parent: dbbdb0ac0c7f7f41541b71d042519b5bdb0b95a8
author: phil9 <telephil9@gmail.com>
date: Fri Nov 26 16:14:18 EST 2021
rename ifilter to cfilter
--- a/README
+++ b/README
@@ -5,9 +5,9 @@
Filters read an image from standard input, apply a transformation
and dumps the resulting image to standard output.
-ifilter:
+cfilter:
--------
-ifilter implements basic color filters.
+cfilter implements basic color filters.
Usage: cfilter [-f factor] [grayscale|sepia|invert|shade|tint]
--- /dev/null
+++ b/cfilter.c
@@ -1,0 +1,131 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+
+#define MIN(x,y) ((x)<(y)?(x):(y))
+
+typedef struct Filter Filter;
+
+struct Filter
+{+ const char *name;
+ void (*filter)(uchar[3], float);
+};
+
+void
+grayscale(uchar p[3], float)
+{+ uchar v = 0.2126*p[2] + 0.7152*p[1] + 0.0722*p[0];
+ p[0] = p[1] = p[2] = v;
+}
+
+void
+sepia(uchar p[3], float)
+{+ float r, g, b;
+
+ r = 0.393*p[2] + 0.769*p[1] + 0.189*p[0];
+ g = 0.349*p[2] + 0.686*p[1] + 0.168*p[0];
+ b = 0.272*p[2] + 0.534*p[1] + 0.131*p[0];
+ p[2] = MIN(r, 255);
+ p[1] = MIN(g, 255);
+ p[0] = MIN(b, 255);
+}
+
+void
+invert(uchar p[3], float)
+{+ p[0] = 255 - p[0];
+ p[1] = 255 - p[1];
+ p[2] = 255 - p[2];
+}
+
+void
+shade(uchar p[3], float factor)
+{+ p[0] = p[0] * (1 - factor);
+ p[1] = p[1] * (1 - factor);
+ p[2] = p[2] * (1 - factor);
+}
+
+void
+tint(uchar p[3], float factor)
+{+ p[0] = p[0] + (255.0 - p[0]) * factor;
+ p[1] = p[1] + (255.0 - p[1]) * factor;
+ p[2] = p[2] + (255.0 - p[2]) * factor;
+}
+
+void
+usage(void)
+{+ fprint(2, "usage: %s [-f factor] [grayscale|sepia|invert|shade|tint]\n", argv0);
+ exits("usage");+}
+
+static Filter filters[] = {+ { "grayscale", grayscale },+ { "sepia", sepia },+ { "invert", invert },+ { "shade", shade },+ { "tint", tint },+};
+
+void
+main(int argc, char *argv[])
+{+ Memimage *o, *i;
+ int w, h, p, n;
+ uchar *buf;
+ Filter *f;
+ float factor;
+
+ f = nil;
+ factor = 0.0;
+ ARGBEGIN{+ case 'f':
+ factor = (float)atof(EARGF(usage()));
+ break;
+ default:
+ usage();
+ break;
+ }ARGEND;
+ if(argc!=1)
+ usage();
+ for(n=0; n<nelem(filters); n++){+ if(strcmp(*argv, filters[n].name)==0){+ f = filters+n;
+ break;
+ }
+ }
+ if(f==nil)
+ usage();
+ if(factor<0.0 || factor>1.0){+ fprint(2, "factor should be between 0.0 and 1.0\n");
+ exits("invalid factor");+ }
+ if(memimageinit()<0)
+ sysfatal("memimageinit: %r");+ o = readmemimage(0);
+ if(o==nil)
+ sysfatal("readmemimage: %r");+ i = allocmemimage(o->r, XRGB32);
+ memimagedraw(i, i->r, o, o->r.min, nil, ZP, S);
+ freememimage(o);
+ w = Dx(i->r);
+ h = Dy(i->r);
+ n = 4*w*h*sizeof(uchar);
+ buf = malloc(n);
+ if(buf==nil)
+ sysfatal("malloc: %r");+ if(unloadmemimage(i, i->r, buf, n)<0)
+ sysfatal("unloadmemimage: %r");+ freememimage(i);
+ for(p = 0; p < n; p+=4)
+ f->filter(buf+p, factor);
+ print(" x8r8g8b8 %11d %11d %11d %11d ", 0, 0, w, h);+ write(1, buf, n);
+ exits(nil);
+}
+