Added option to TIFF handler for specifying the photometric interpretation.

Added option wxIMAGE_OPTION_TIFF_PHOTOMETRIC for reading and writing TIFF images. This is mostly for being able to distinguish between PHOTOMETRIC_MINISBLACK (chocolate flavour) and PHOTOMETRIC_MINISWHITE (vanilla) as currently the flavour used was fixed. It applies to greyscale as well as black and white images. Added unit tests to verify the written photometric value.

Also see #13194.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68785 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/imagtiff.h

@@ -25,6 +25,7 @@
 #define wxIMAGE_OPTION_TIFF_BITSPERSAMPLE               wxString(wxT("BitsPerSample"))
 #define wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL             wxString(wxT("SamplesPerPixel"))
 #define wxIMAGE_OPTION_TIFF_COMPRESSION                 wxString(wxT("Compression"))
+#define wxIMAGE_OPTION_TIFF_PHOTOMETRIC                 wxString(wxT("Photometric"))
 #define wxIMAGE_OPTION_TIFF_IMAGEDESCRIPTOR             wxString(wxT("ImageDescriptor"))
 
 // for backwards compatibility

src/common/imagtiff.cpp

@@ -437,6 +437,8 @@ bool wxTIFFHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbos
     }
 
 
+    image->SetOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC, photometric);
+
     uint16 spp, bps, compression;
     /*
     Read some baseline TIFF tags which helps when re-saving a TIFF
@@ -603,6 +605,27 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
         spp = 1;
     }
 
+    int photometric = PHOTOMETRIC_RGB;
+
+    if ( image->HasOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC) )
+    {
+        photometric = image->GetOptionInt(wxIMAGE_OPTION_TIFF_PHOTOMETRIC);
+        if (photometric == PHOTOMETRIC_MINISWHITE
+            || photometric == PHOTOMETRIC_MINISBLACK)
+        {
+            // either b/w or greyscale
+            spp = 1;
+        }
+    }
+    else if (spp == 1)
+    {
+        photometric = PHOTOMETRIC_MINISBLACK;
+    }
+
+    const bool isColouredImage = (spp > 1)
+        && (photometric != PHOTOMETRIC_MINISWHITE)
+        && (photometric != PHOTOMETRIC_MINISBLACK);
+
     int compression = image->GetOptionInt(wxIMAGE_OPTION_TIFF_COMPRESSION);
     if ( !compression )
     {
@@ -615,8 +638,7 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
 
     TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, spp);
     TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, bps);
-    TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, spp*bps == 1 ? PHOTOMETRIC_MINISBLACK
+    TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, photometric);
-                                                        : PHOTOMETRIC_RGB);
     TIFFSetField(tif, TIFFTAG_COMPRESSION, compression);
 
     // scanlinesize if determined by spp and bps
@@ -627,7 +649,7 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
 
     unsigned char *buf;
 
-    if (TIFFScanlineSize(tif) > linebytes || (spp * bps < 24))
+    if (TIFFScanlineSize(tif) > linebytes || !isColouredImage)
     {
         buf = (unsigned char *)_TIFFmalloc(TIFFScanlineSize(tif));
         if (!buf)
@@ -649,12 +671,13 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
 
     TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP,TIFFDefaultStripSize(tif, (uint32) -1));
 
+    const bool minIsWhite = (photometric == PHOTOMETRIC_MINISWHITE);
     unsigned char *ptr = image->GetData();
     for ( int row = 0; row < image->GetHeight(); row++ )
     {
         if ( buf )
         {
-            if ( spp * bps > 1 )
+            if (isColouredImage)
             {
                 // color image
                 memcpy(buf, ptr, image->GetWidth());
@@ -663,7 +686,13 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
             {
                 for ( int column = 0; column < linebytes; column++ )
                 {
-                    buf[column] = ptr[column*3 + 1];
+                    uint8 value = ptr[column*3 + 1];
+                    if (minIsWhite)
+                    {
+                        value = 255 - value;
+                    }
+
+                    buf[column] = value;
                 }
             }
             else // black and white image
@@ -673,7 +702,7 @@ bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
                     uint8 reverse = 0;
                     for ( int bp = 0; bp < 8; bp++ )
                     {
-                        if ( ptr[column*24 + bp*3 + 1] > 127 )
+                        if ( (ptr[column*24 + bp*3 + 1] <=127) == minIsWhite )
                         {
                             // check only green as this is sufficient
                             reverse = (uint8)(reverse | 128 >> bp);

tests/image/image.cpp

@@ -1116,6 +1116,8 @@ void ImageTestCase::SaveTIFF()
 {
     TestTIFFImage(wxIMAGE_OPTION_TIFF_BITSPERSAMPLE, 1);
     TestTIFFImage(wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL, 1);
+    TestTIFFImage(wxIMAGE_OPTION_TIFF_PHOTOMETRIC, 0/*PHOTOMETRIC_MINISWHITE*/);
+    TestTIFFImage(wxIMAGE_OPTION_TIFF_PHOTOMETRIC, 1/*PHOTOMETRIC_MINISBLACK*/);
 }
 
 void ImageTestCase::SaveAnimatedGIF()