From 5339040ebdf88f5e8df912586962bcd2fcda0333 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Fri, 20 Dec 2019 15:53:50 +0100
Subject: [PATCH] support TIFF predictor for BitsPerComponent = 8
---
pdf.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/pdf.c b/pdf.c
index 72b33ef..6a74caf 100644
--- a/pdf.c
+++ b/pdf.c
@@ -622,7 +622,8 @@ depred_png(struct predictor *pred, uint8_t *inp, size_t sz)
if (x == pred->rowsz) {
done = h_parse_chunk(pred->sp, pred->buf, pred->rowsz);
pred->c = pred->x = 0;
- pred->predfun = NULL;
+ if (pred->num != 2) /* support for 8-bpc TIFF */
+ pred->predfun = NULL;
}
}
@@ -660,10 +661,21 @@ FlateDecode(HAllocator *mm__, HCountedArray *parms, HBytes b, HParser *p)
if (pred.num == 1)
depredict = depred_none;
else {
- // XXX add TIFF predictor
if (pred.num >= 10 && pred.num <= 15)
depredict = depred_png;
- else {
+ else if (pred.num == 2) {
+ /* for 8-bpc TIFF pred. 2, we can reuse PNG Sub */
+ if (pred.bpc == 8) {
+ pred.predfun = pp_sub; /* predict left */
+ depredict = depred_png;
+ } else {
+ // XXX add general TIFF predictor (bpc != 8)
+ fprintf(stderr, "FlateDecode: /Predictor %d "
+ "not supported for /BitsPerComponent %d\n",
+ pred.num, pred.bpc);
+ return NULL;
+ }
+ } else {
fprintf(stderr, "FlateDecode: /Predictor %d"
" not supported\n", pred.num);
return NULL;
--
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