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tif: rescale palette color map to [0, 255]

--- a/sys/src/cmd/jpg/readtif.c

+++ b/sys/src/cmd/jpg/readtif.c

@@ -1286,10 +1286,16 @@

 paldecode(Tif *t, Rawimage *im, uchar *data)

 {

 	int pix, pmask, xmask;

-	ulong i, n, x, y, *r, *g, *b;

+	ulong i, n, x, y, *r, *g, *b, max;

 	pmask = (1 << t->depth) - 1;

 	xmask = 7 >> log2[t->depth];

+	for(i = max = 0; i < t->ncolor; i++) {

+		if(t->color[i] > max)

+			max = t->color[i];

+	}

+	for(i = 0; i < t->ncolor; i++)

+		t->color[i] = (t->color[i] * 0xff) / max;

 	r = t->color;

 	g = r + pmask + 1;

 	b = g + pmask + 1;

-- 

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