diff --git a/26_day/sheet.c b/26_day/sheet.c
index a51c756..eb2a10b 100644
--- a/26_day/sheet.c
+++ b/26_day/sheet.c
@@ -75,14 +75,26 @@ void sheet_refreshmap(struct SHTCTL *ctl, int vx0, int vy0, int vx1, int vy1, in
 		if (by0 < 0) { by0 = 0; }
 		if (bx1 > sht->bxsize) { bx1 = sht->bxsize; }
 		if (by1 > sht->bysize) { by1 = sht->bysize; }
-		for (by = by0; by < by1; by++) {
-			vy = sht->vy0 + by;
-			for (bx = bx0; bx < bx1; bx++) {
-				vx = sht->vx0 + bx;
-				if (buf[by * sht->bxsize + bx] != sht->col_inv) {
+		if (sht->col_inv == -1) {
+			/*无透明色图层专用的高速版*/
+			for (by = by0; by < by1; by++) {
+				vy = sht->vy0 + by;
+				for (bx = bx0; bx < bx1; bx++) {
+					vx = sht->vx0 + bx;
 					map[vy * ctl->xsize + vx] = sid;
 				}
 			}
+		} else {
+			/*有透明色图层用的普通版*/
+			for (by = by0; by < by1; by++) {
+				vy = sht->vy0 + by;
+				for (bx = bx0; bx < bx1; bx++) {
+					vx = sht->vx0 + bx;
+					if (buf[by * sht->bxsize + bx] != sht->col_inv) {
+						map[vy * ctl->xsize + vx] = sid;
+					}
+				}
+			}
 		}
 	}
 	return;