From 62d3736392611f6b21ad20719f8bd52096f1cca3 Mon Sep 17 00:00:00 2001
From: Frank Warmerdam <warmerdam@pobox.com>
Date: Sat, 15 Dec 2001 15:11:22 +0000
Subject: [PATCH] bug 93: default unmarked 4th sample as alpha

---
 ChangeLog              | 12 ++++++++++++
 libtiff/tif_getimage.c | 18 +++++++++++++++++-
 libtiff/tiffconf.h     | 11 ++++++++++-
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 404aad8d..b0e99640 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2001-12-15  Frank Warmerdam  <warmerdam@pobox.com>
+
+	* libtiff/tif_getimage.c: If DEFAULT_EXTRASAMPLE_AS_ALPHA is 1 
+	(defined in tiffconf.h - 1 by default) then the RGBA interface
+	will assume that a fourth extra sample is ASSOCALPHA if the
+	EXTRASAMPLE value isn't set for it.  This changes the behaviour of
+	the library, but makes it work better with RGBA files produced by
+	lots of applications that don't mark the alpha values properly.
+
+	http://bugzilla.remotesensing.org/show_bug.cgi?id=93
+	http://bugzilla.remotesensing.org/show_bug.cgi?id=65
+
 2001-12-12  Frank Warmerdam  <warmerdam@pobox.com>
 
 	* libtiff/tif_jpeg.c: allow jpeg data stream sampling values to 
diff --git a/libtiff/tif_getimage.c b/libtiff/tif_getimage.c
index 89c621e5..ed270765 100644
--- a/libtiff/tif_getimage.c
+++ b/libtiff/tif_getimage.c
@@ -1,4 +1,4 @@
-/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/tif_getimage.c,v 1.15 2001-09-24 19:40:37 warmerda Exp $ */
+/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/tif_getimage.c,v 1.16 2001-12-15 15:11:22 warmerda Exp $ */
 
 /*
  * Copyright (c) 1991-1997 Sam Leffler
@@ -220,12 +220,28 @@ TIFFRGBAImageBegin(TIFFRGBAImage* img, TIFF* tif, int stop, char emsg[1024])
     TIFFGetFieldDefaulted(tif, TIFFTAG_EXTRASAMPLES,
 	&extrasamples, &sampleinfo);
     if (extrasamples == 1)
+    {
 	switch (sampleinfo[0]) {
 	case EXTRASAMPLE_ASSOCALPHA:	/* data is pre-multiplied */
 	case EXTRASAMPLE_UNASSALPHA:	/* data is not pre-multiplied */
 	    img->alpha = sampleinfo[0];
 	    break;
 	}
+    }
+
+#if DEFAULT_EXTRASAMPLE_AS_ALPHA == 1
+    if( !TIFFGetField(tif, TIFFTAG_PHOTOMETRIC, &img->photometric))
+        img->photometric = PHOTOMETRIC_MINISWHITE;
+
+    if( extrasamples == 0 
+        && img->samplesperpixel == 4 
+        && img->photometric == PHOTOMETRIC_RGB )
+    {
+        img->alpha = EXTRASAMPLE_ASSOCALPHA;
+        extrasamples = 1;
+    }
+#endif
+
     colorchannels = img->samplesperpixel - extrasamples;
     TIFFGetFieldDefaulted(tif, TIFFTAG_COMPRESSION, &compress);
     TIFFGetFieldDefaulted(tif, TIFFTAG_PLANARCONFIG, &planarconfig);
diff --git a/libtiff/tiffconf.h b/libtiff/tiffconf.h
index ef1e6cf0..c6e33d73 100644
--- a/libtiff/tiffconf.h
+++ b/libtiff/tiffconf.h
@@ -1,4 +1,4 @@
-/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/Attic/tiffconf.h,v 1.3 2001-05-12 03:59:50 warmerda Exp $ */
+/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/Attic/tiffconf.h,v 1.4 2001-12-15 15:11:22 warmerda Exp $ */
 /*
  * Copyright (c) 1988-1997 Sam Leffler
  * Copyright (c) 1991-1997 Silicon Graphics, Inc.
@@ -133,6 +133,11 @@
  *			or not to convert single-strip uncompressed images
  *			to mutiple strips of ~8Kb--to reduce memory use)
  * SUBIFD_SUPPORT	enable support for SubIFD tag (thumbnails and such)
+ * DEFAULT_EXTRASAMPLE_AS_ALPHA
+ *                      The RGBA interface will treat a fourth sample with
+ *                      no EXTRASAMPLE_ value as being ASSOCALPHA.  Many
+ *                      packages produce RGBA files but don't mark the alpha
+ *                      properly.
  */
 #ifndef STRIPCHOP_DEFAULT
 #define	STRIPCHOP_DEFAULT	TIFF_STRIPCHOP	/* default is to enable */
@@ -140,4 +145,8 @@
 #ifndef SUBIFD_SUPPORT
 #define	SUBIFD_SUPPORT		1	/* enable SubIFD tag (330) support */
 #endif
+#ifndef DEFAULT_EXTRASAMPLE_AS_ALPHA
+#define DEFAULT_EXTRASAMPLE_AS_ALPHA 1
+#endif
+
 #endif /* _TIFFCONF_ */