From 2bea824153d19b3dbf6164187291a9c90e759b05 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Mon, 22 Sep 2014 02:37:44 +0200
Subject: [PATCH] mtwebmapper: simplified pyramid tile updater a bit.

---
 cmd/mtwebmapper/tilesupdater.go | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/cmd/mtwebmapper/tilesupdater.go b/cmd/mtwebmapper/tilesupdater.go
index 9abfd79..8a60609 100644
--- a/cmd/mtwebmapper/tilesupdater.go
+++ b/cmd/mtwebmapper/tilesupdater.go
@@ -56,15 +56,6 @@ func (c xz) parent() xzm {
 		Mask: 1 << (zr<<1 | xr)}
 }
 
-func (c xzm) numChanges() (n int) {
-	for i := uint16(0); i < 4; i++ {
-		if c.Mask&(1<<i) != 0 {
-			n++
-		}
-	}
-	return
-}
-
 func newTileUpdater(mapDir, redisAddress string, colors *common.Colors, workers int) *tileUpdater {
 	tu := tileUpdater{
 		mapDir:       mapDir,
@@ -177,7 +168,6 @@ func updatePyramidTiles(level int, baseDir string, jobs chan xzm, done *sync.Wai
 
 /*
   (0,0)    (128, 0)
-
   (0, 128) (128, 128)
 */
 
@@ -206,10 +196,6 @@ func updatePyramidTile(scratch *image.RGBA, level int, baseDir string, j xzm) er
 		strconv.Itoa(int(j.P.X)),
 		fmt.Sprintf("%d.png", j.P.Z))
 
-	if j.numChanges() < 4 {
-		orig = common.LoadPNG(origPath)
-	}
-
 	for i := uint16(0); i < 4; i++ {
 		if j.Mask&(1<<i) != 0 {
 			//log.Printf("level %d: modified %d", level, i)
@@ -226,10 +212,14 @@ func updatePyramidTile(scratch *image.RGBA, level int, baseDir string, j xzm) er
 			r := sr.Sub(sr.Min).Add(dps[i])
 			draw.Draw(scratch, r, img, sr.Min, draw.Src)
 		} else {
+			// Load lazy
+			if orig == nil {
+				orig = common.LoadPNG(origPath)
+			}
 			//log.Printf("level %d: copied %d", level, i)
 			min := orig.Bounds().Min.Add(dps[i])
 			r := image.Rectangle{min, min.Add(windowSize)}
-			draw.Draw(scratch, r, orig, orig.Bounds().Min.Add(dps[i]), draw.Src)
+			draw.Draw(scratch, r, orig, min, draw.Src)
 		}
 	}