From 80ff420366dd1086c434a003b2f5b7bdfa2468cd Mon Sep 17 00:00:00 2001
From: Tor Andersson <tor@ghostscript.com>
Date: Thu, 28 Oct 2010 16:01:52 +0000
Subject: Patch for initializing weights when the downscale of the image is so
 severe we end up with no non-zero weights for a given output pixel. By Robin
 Watts.

---
 draw/imagesmooth.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

(limited to 'draw')

diff --git a/draw/imagesmooth.c b/draw/imagesmooth.c
index 1bdbedf7..c564ccbf 100644
--- a/draw/imagesmooth.c
+++ b/draw/imagesmooth.c
@@ -250,6 +250,7 @@ struct fz_weights_s
 	int max_len;
 	int n;
 	int flip;
+	int new_line;
 	int index[1];
 };
 
@@ -291,6 +292,26 @@ newweights(fz_scalefilter *filter, int src_w, float dst_w, int dst_w_i, int n, i
 	return weights;
 }
 
+static void
+init_weights(fz_weights *weights, int j)
+{
+	int index;
+
+	assert(weights->count == j-1);
+	weights->count++;
+	weights->new_line = 1;
+	if (j == 0)
+		index = weights->index[0];
+	else
+	{
+		index = weights->index[j-1];
+		index += 2 + weights->index[index+1];
+	}
+	weights->index[j] = index; /* row pointer */
+	weights->index[index] = 0; /* min */
+	weights->index[index+1] = 0; /* len */
+}
+
 static void
 add_weight(fz_weights *weights, int j, int i, fz_scalefilter *filter,
 	float x, float F, float G, int src_w, float dst_w)
@@ -339,19 +360,11 @@ add_weight(fz_weights *weights, int j, int i, fz_scalefilter *filter,
 
 	DBUG(("add_weight[%d][%d] = %d(%g) dist=%g\n",j,i,weight,f,dist));
 
-	if (weights->count != j)
+	if (weights->new_line)
 	{
 		/* New line */
-		assert(weights->count == j-1);
-		weights->count++;
-		if (j == 0)
-			index = weights->index[0];
-		else
-		{
-			index = weights->index[j-1];
-			index += 2 + weights->index[index+1];
-		}
-		weights->index[j] = index; /* row pointer */
+		weights->new_line = 0;
+		index = weights->index[j]; /* row pointer */
 		weights->index[index] = i; /* min */
 		weights->index[index+1] = 0; /* len */
 	}
@@ -492,6 +505,7 @@ make_weights(int src_w, float x, float dst_w, fz_scalefilter *filter, int vertic
 		l = ceilf(centre - window);
 		r = floorf(centre + window);
 		DBUG(("%d: centre=%g l=%d r=%d\n", j, centre, l, r));
+		init_weights(weights, j);
 		for (; l <= r; l++)
 		{
 			add_weight(weights, j, l, filter, x, F, G, src_w, dst_w);
-- 
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