shithub: riscv

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libmemdraw: update drawtest to use same rounding in alpha calculation as libmemdraw

--- a/sys/src/libmemdraw/drawtest.c

+++ b/sys/src/libmemdraw/drawtest.c

@@ -974,7 +974,7 @@

 	pixtorgba(getpixel(dst, dp), &dr, &dg, &db, &da);

 	pixtorgba(getpixel(src, sp), &sr, &sg, &sb, &sa);

 	m = getmask(mask, mp);

-	M = 255-(sa*m)/255;

+	M = 255-(sa*m + 127)/255;

 DBG print("dst %x %x %x %x src %x %x %x %x m %x = ", dr,dg,db,da, sr,sg,sb,sa, m);

 	if(dst->flags&Fgrey){

@@ -985,18 +985,18 @@

 		 */

 		sk = RGB2K(sr, sg, sb);

 		dk = RGB2K(dr, dg, db);

-		dk = (sk*m + dk*M)/255;

+		dk = (sk*m + dk*M + 127)/255;

 		dr = dg = db = dk;

-		da = (sa*m + da*M)/255;

+		da = (sa*m + da*M + 127)/255;

 	}else{

 		/*

 		 * True color alpha calculation treats all channels (including alpha)

 		 * the same.  It might have been nice to use an array, but oh well.

 		 */

-		dr = (sr*m + dr*M)/255;

-		dg = (sg*m + dg*M)/255;

-		db = (sb*m + db*M)/255;

-		da = (sa*m + da*M)/255;

+		dr = (sr*m + dr*M + 127)/255;

+		dg = (sg*m + dg*M + 127)/255;

+		db = (sb*m + db*M + 127)/255;

+		da = (sa*m + da*M + 127)/255;

 	}

 DBG print("%x %x %x %x\n", dr,dg,db,da);