Why not?

src/cmd/jpg/multichan.c

@@ -0,0 +1,60 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <bio.h>
+#include "imagefile.h"
+
+/* Separate colors, if not a grey scale or bitmap, into one byte per color per pixel, no alpha or X */
+/* Result is GREY[1248] or RGB24 */
+
+int drawlog2[] = {
+	0, 0, 1, 0, 2, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0,
+	4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	5
+};
+
+static
+int
+notrans(ulong chan)
+{
+	switch(chan){
+	case GREY1:
+	case GREY2:
+	case GREY4:
+	case GREY8:
+	case RGB24:
+		return 1;
+	}
+	return 0;
+}
+
+Image*
+multichan(Image *i)
+{
+	Image *ni;
+
+	if(notrans(i->chan))
+		return i;
+
+	ni = allocimage(display, i->r, RGB24, 0, DNofill);
+	if(ni == nil)
+		return ni;
+	draw(ni, ni->r, i, nil, i->r.min);
+	return ni;
+}
+
+Memimage*
+memmultichan(Memimage *i)
+{
+	Memimage *ni;
+
+	if(notrans(i->chan))
+		return i;
+
+	ni = allocmemimage(i->r, RGB24);
+	if(ni == nil)
+		return ni;
+	memimagedraw(ni, ni->r, i, i->r.min, nil, i->r.min, S);
+	return ni;
+}