Initial revision
diff --git a/src/libdraw/chan.c b/src/libdraw/chan.c
new file mode 100644
index 0000000..3b76a32
--- /dev/null
+++ b/src/libdraw/chan.c
@@ -0,0 +1,77 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+
+static char channames[] = "rgbkamx";
+char*
+chantostr(char *buf, u32int cc)
+{
+ u32int c, rc;
+ char *p;
+
+ if(chantodepth(cc) == 0)
+ return nil;
+
+ /* reverse the channel descriptor so we can easily generate the string in the right order */
+ rc = 0;
+ for(c=cc; c; c>>=8){
+ rc <<= 8;
+ rc |= c&0xFF;
+ }
+
+ p = buf;
+ for(c=rc; c; c>>=8) {
+ *p++ = channames[TYPE(c)];
+ *p++ = '0'+NBITS(c);
+ }
+ *p = 0;
+
+ return buf;
+}
+
+/* avoid pulling in ctype when using with drawterm etc. */
+static int
+isspace(char c)
+{
+ return c==' ' || c== '\t' || c=='\r' || c=='\n';
+}
+
+u32int
+strtochan(char *s)
+{
+ char *p, *q;
+ u32int c;
+ int t, n;
+
+ c = 0;
+ p=s;
+ while(*p && isspace(*p))
+ p++;
+
+ while(*p && !isspace(*p)){
+ if((q = strchr(channames, p[0])) == nil)
+ return 0;
+ t = q-channames;
+ if(p[1] < '0' || p[1] > '9')
+ return 0;
+ n = p[1]-'0';
+ c = (c<<8) | __DC(t, n);
+ p += 2;
+ }
+ return c;
+}
+
+int
+chantodepth(u32int c)
+{
+ int n;
+
+ for(n=0; c; c>>=8){
+ if(TYPE(c) >= NChan || NBITS(c) > 8 || NBITS(c) <= 0)
+ return 0;
+ n += NBITS(c);
+ }
+ if(n==0 || (n>8 && n%8) || (n<8 && 8%n))
+ return 0;
+ return n;
+}
