issue 1440: the plain-lid test's specks lie where counting them would make a box

modules/scan/cmd/scan/crop_test.go

@@ -10,13 +10,13 @@ import (
 	"testing"
 )
 
-// lidWhite is a w x h gray image of the lid's white, with a few specks of dust.
+// lidWhite is a w x h gray image of the lid's white, with a few specks of dust in one patch.
 func lidWhite(w, h int, seed int64) *image.Gray {
 	g := image.NewGray(image.Rect(0, 0, w, h))
 	draw.Draw(g, g.Bounds(), &image.Uniform{color.Gray{255}}, image.Point{}, draw.Src)
 	r := rand.New(rand.NewSource(seed))
 	for i := 0; i < 40; i++ {
-		g.SetGray(r.Intn(w), r.Intn(h), color.Gray{120})
+		g.SetGray(100+r.Intn(w/4), 100+r.Intn(h/4), color.Gray{120}) // all in one patch, so counting them would make a box
 	}
 	return g
 }