ref: 558bc6b21da1130b09dfb09d216736f88016c1c6
author: phil9 <telephil9@gmail.com>
date: Sat Sep 4 18:34:26 EDT 2021
initial import
--- /dev/null
+++ b/README
@@ -1,0 +1,13 @@
+ifilter
+=======
+Basic image color filters.
+
+ifilter reads an image from standard input, applies a color filter
+and dumps the resulting image to standard output.
+
+Available color filters are:
+- grayscale
+- sepia
+
+usage: ifilter [grayscale|sepia]
+
--- /dev/null
+++ b/ifilter.c
@@ -1,0 +1,78 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+
+#define MIN(x,y) ((x)<(y)?(x):(y))
+
+typedef void(*filterfun)(uchar[3]);
+
+void
+grayscale(uchar p[3])
+{+ uchar v = 0.2126*p[0] + 0.7152*p[1] + 0.0722*p[2];
+ p[0] = p[1] = p[2] = v;
+}
+
+void
+sepia(uchar p[3])
+{+ 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
+usage(void)
+{+ fprint(2, "usage: %s [grayscale|sepia]\n", argv0);
+ exits("usage");+}
+
+void
+main(int argc, char *argv[])
+{+ Memimage *i;
+ int w, h, p, n;
+ uchar *buf;
+ filterfun filter;
+
+ filter = nil;
+ ARGBEGIN{+ }ARGEND;
+ if(argc!=1)
+ usage();
+ if(strcmp(*argv, "grayscale")==0)
+ filter = grayscale;
+ else if(strcmp(*argv, "sepia")==0)
+ filter = sepia;
+ else
+ usage();
+ if(memimageinit()<0)
+ sysfatal("memimageinit: %r");+ i = readmemimage(0);
+ if(i==nil)
+ sysfatal("readmemimage: %r");+ 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");+ for(p = 0; p < n; p+=4){+ filter(buf+p);
+ }
+ if(loadmemimage(i, i->r, buf, n)<0)
+ sysfatal("unloadmemimage: %r");+ writememimage(1, i);
+ freememimage(i);
+ exits(nil);
+}
+
--- /dev/null
+++ b/mkfile
@@ -1,0 +1,9 @@
+</$objtype/mkfile
+
+BIN=/$objtype/bin
+CFLAGS=-FTVw
+TARG=ifilter
+OFILES=ifilter.$O
+
+</sys/src/cmd/mkone
+