diff --git a/cmd/mtseeder/pyramid.go b/cmd/mtseeder/pyramid.go
index 8e62860..23609d0 100644
--- a/cmd/mtseeder/pyramid.go
+++ b/cmd/mtseeder/pyramid.go
@@ -169,7 +169,7 @@ func fuseTile(scratch *image.RGBA, job *pyramidJob) (err error) {
 		draw.Draw(scratch, r, img, sr.Min, draw.Src)
 	}
 
-	resized := resize.Resize(256, 256, scratch, resize.Bicubic)
+	resized := resize.Resize(256, 256, scratch, resize.Lanczos3)
 
 	var outFile *os.File
 	if outFile, err = os.Create(job.dst); err != nil {
diff --git a/common/renderer.go b/common/renderer.go
index 34e9a68..c329bf7 100644
--- a/common/renderer.go
+++ b/common/renderer.go
@@ -346,11 +346,20 @@ func (r *Renderer) CreateShadedImage(
 
 	stride := pw - width
 
+	istride := image.Stride + 4*width
+
+	iofs := image.PixOffset(0, height-1)
+
+	pix := image.Pix
+
 	for z := height - 1; z >= 0; z-- {
 		for x := 0; x < width; x++ {
 			colIdx := r.cBuffer[ofs]
 			if colIdx < 0 || colIdx >= numCols {
-				image.Set(x, z, background)
+				pix[iofs] = background.R
+				pix[iofs+1] = background.G
+				pix[iofs+2] = background.B
+				pix[iofs+3] = 0xff
 			} else {
 				var y, y1, y2 int32
 				y = r.yBuffer[ofs]
@@ -369,15 +378,16 @@ func (r *Renderer) CreateShadedImage(
 					d = 36
 				}
 				col := colors[colIdx]
-				image.Set(x, z, color.RGBA{
-					R: safeColor(int32(col.R) + d),
-					G: safeColor(int32(col.G) + d),
-					B: safeColor(int32(col.B) + d),
-					A: 0xff})
+				pix[iofs] = safeColor(int32(col.R) + d)
+				pix[iofs+1] = safeColor(int32(col.G) + d)
+				pix[iofs+2] = safeColor(int32(col.B) + d)
+				pix[iofs+3] = 0xff
 			}
+			iofs += 4
 			ofs++
 		}
 		ofs += stride
+		iofs -= istride
 	}
 	return image
 }