added support for image resolution options to PNG handler (heavily modified patch 1704128)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45567 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/image.h

@@ -37,9 +37,17 @@
 #define wxIMAGE_OPTION_RESOLUTIONUNIT        wxString(_T("ResolutionUnit"))
 
 // constants used with wxIMAGE_OPTION_RESOLUTIONUNIT
-enum
+//
+// NB: don't change these values, they correspond to libjpeg constants
+enum wxImageResolution
 {
+    // Resolution not specified
+    wxIMAGE_RESOLUTION_NONE = 0,
+
+    // Resolution specified in inches
     wxIMAGE_RESOLUTION_INCHES = 1,
+
+    // Resolution specified in centimeters
     wxIMAGE_RESOLUTION_CM = 2
 };
 
@@ -112,6 +120,13 @@ protected:
     bool CallDoCanRead(wxInputStream& stream);
 #endif // wxUSE_STREAMS
 
+    // helper for the derived classes SaveFile() implementations: returns the
+    // values of x- and y-resolution options specified as the image options if
+    // any
+    static wxImageResolution
+    GetResolutionFromOptions(const wxImage& image, int *x, int *y);
+
+
     wxString  m_name;
     wxString  m_extension;
     wxString  m_mime;

src/common/image.cpp

@@ -2645,6 +2645,42 @@ bool wxImageHandler::CallDoCanRead(wxInputStream& stream)
 
 #endif // wxUSE_STREAMS
 
+/* static */
+wxImageResolution
+wxImageHandler::GetResolutionFromOptions(const wxImage& image, int *x, int *y)
+{
+    wxCHECK_MSG( x && y, wxIMAGE_RESOLUTION_NONE, _T("NULL pointer") );
+
+    if ( image.HasOption(wxIMAGE_OPTION_RESOLUTIONX) &&
+         image.HasOption(wxIMAGE_OPTION_RESOLUTIONY) )
+    {
+        *x = image.GetOptionInt(wxIMAGE_OPTION_RESOLUTIONX);
+        *y = image.GetOptionInt(wxIMAGE_OPTION_RESOLUTIONY);
+    }
+    else if ( image.HasOption(wxIMAGE_OPTION_RESOLUTION) )
+    {
+        *x =
+        *y = image.GetOptionInt(wxIMAGE_OPTION_RESOLUTION);
+    }
+    else // no resolution options specified
+    {
+        *x =
+        *y = 0;
+
+        return wxIMAGE_RESOLUTION_NONE;
+    }
+
+    // get the resolution unit too
+    int resUnit = image.GetOptionInt(wxIMAGE_OPTION_RESOLUTIONUNIT);
+    if ( !resUnit )
+    {
+        // this is the default
+        resUnit = wxIMAGE_RESOLUTION_INCHES;
+    }
+
+    return (wxImageResolution)resUnit;
+}
+
 // ----------------------------------------------------------------------------
 // image histogram stuff
 // ----------------------------------------------------------------------------

src/common/imagjpeg.cpp

@@ -414,37 +414,16 @@ bool wxJPEGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
         jpeg_set_quality(&cinfo, image->GetOptionInt(wxIMAGE_OPTION_QUALITY), TRUE);
 
     // set the resolution fields in the output file
-    UINT16 resX,
+    int resX, resY;
-           resY;
+    wxImageResolution res = GetResolutionFromOptions(*image, &resX, &resY);
-    if ( image->HasOption(wxIMAGE_OPTION_RESOLUTIONX) &&
+    if ( res != wxIMAGE_RESOLUTION_NONE )
-         image->HasOption(wxIMAGE_OPTION_RESOLUTIONY) )
-    {
-        resX = (UINT16)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTIONX);
-        resY = (UINT16)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTIONY);
-    }
-    else if ( image->HasOption(wxIMAGE_OPTION_RESOLUTION) )
-    {
-        resX =
-        resY = (UINT16)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTION);
-    }
-    else
-    {
-        resX =
-        resY = 0;
-    }
-
-    if ( resX && resY )
     {
         cinfo.X_density = resX;
         cinfo.Y_density = resY;
-    }
 
-    // sets the resolution unit field in the output file
+        // it so happens that wxIMAGE_RESOLUTION_INCHES/CM values are the same
-    // wxIMAGE_RESOLUTION_INCHES for inches
+        // ones as used by libjpeg, so we can assign them directly
-    // wxIMAGE_RESOLUTION_CM for centimeters
+        cinfo.density_unit = res;
-    if ( image->HasOption(wxIMAGE_OPTION_RESOLUTIONUNIT) )
-    {
-        cinfo.density_unit = (UINT8)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTIONUNIT);
     }
 
     jpeg_start_compress(&cinfo, TRUE);

src/common/imagpng.cpp

@@ -63,6 +63,8 @@ enum Transparency
     Transparency_Alpha
 };
 
+static const double INCHES_IN_METER = 39.3700787;
+
 // ----------------------------------------------------------------------------
 // local functions
 // ----------------------------------------------------------------------------
@@ -748,6 +750,30 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
     if ( iBitDepth == 16 )
         iElements *= 2;
 
+    // save the image resolution if we have it
+    int resX, resY;
+    switch ( GetResolutionFromOptions(*image, &resX, &resY) )
+    {
+        case wxIMAGE_RESOLUTION_INCHES:
+            resX *= INCHES_IN_METER;
+            resY *= INCHES_IN_METER;
+            break;
+
+        case wxIMAGE_RESOLUTION_CM:
+            resX *= 100;
+            resY *= 100;
+            break;
+
+        case wxIMAGE_RESOLUTION_NONE:
+            break;
+
+        default:
+            wxFAIL_MSG( _T("unsupported image resolution units") );
+    }
+
+    if ( resX && resY )
+        png_set_pHYs( png_ptr, info_ptr, resX, resY, PNG_RESOLUTION_METER );
+
     png_set_sBIT( png_ptr, info_ptr, &sig_bit );
     png_write_info( png_ptr, info_ptr );
     png_set_shift( png_ptr, &sig_bit );