implement GetBestSize() (patch 1386199)

[wxWidgets.git] / src / common / imagpng.cpp

diff --git a/src/common/imagpng.cpp b/src/common/imagpng.cpp
index 132655980c64e0e38e6f08eedc30e726491fa890..009f133de98c46fc8d432c4f03ae92d27987c8ba 100644 (file)
--- a/src/common/imagpng.cpp
+++ b/src/common/imagpng.cpp
@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////////
 /////////////////////////////////////////////////////////////////////////////

-// Name:        imagepng.cpp
+// Name:        src/common/imagepng.cpp

 // Purpose:     wxImage PNG handler
 // Author:      Robert Roebling
 // RCS-ID:      $Id$
 // Purpose:     wxImage PNG handler
 // Author:      Robert Roebling
 // RCS-ID:      $Id$


@@ -7,34 +7,37 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 

-/*
-   We don't put pragma implement in this file because it is already present in
-   src/common/image.cpp
-*/
+// ============================================================================
+// declarations
+// ============================================================================
+
+// ----------------------------------------------------------------------------
+// headers
+// ----------------------------------------------------------------------------

 
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
 #ifdef __BORLANDC__
 
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
 #ifdef __BORLANDC__

-  #pragma hdrstop
+    #pragma hdrstop

 #endif
 
 #endif
 

+#if wxUSE_IMAGE && wxUSE_LIBPNG
+
+#include "wx/imagpng.h"
+

 #ifndef WX_PRECOMP
 #ifndef WX_PRECOMP

-  #include "wx/defs.h"
+    #include "wx/log.h"
+    #include "wx/app.h"
+    #include "wx/bitmap.h"
+    #include "wx/module.h"

 #endif
 
 #endif
 

-#if wxUSE_LIBPNG
-
-#include "wx/image.h"
-#include "wx/bitmap.h"
-#include "wx/debug.h"
-#include "wx/log.h"
-#include "wx/app.h"

 #include "png.h"
 #include "wx/filefn.h"
 #include "wx/wfstream.h"
 #include "wx/intl.h"
 #include "png.h"
 #include "wx/filefn.h"
 #include "wx/wfstream.h"
 #include "wx/intl.h"

-#include "wx/module.h"
+#include "wx/palette.h"

 
 // For memcpy
 #include <string.h>
 
 // For memcpy
 #include <string.h>


@@ -45,205 +48,577 @@
 #endif
 #endif
 
 #endif
 #endif
 

-#ifdef __WXMSW__
-#include <windows.h>
-#endif
+// ----------------------------------------------------------------------------
+// constants
+// ----------------------------------------------------------------------------

 
 

-//-----------------------------------------------------------------------------
-// wxPNGHandler
-//-----------------------------------------------------------------------------
+// image can not have any transparent pixels at all, have only 100% opaque
+// and/or 100% transparent pixels in which case a simple mask is enough to
+// store this information in wxImage or have a real alpha channel in which case
+// we need to have it in wxImage as well
+enum Transparency
+{
+    Transparency_None,
+    Transparency_Mask,
+    Transparency_Alpha
+};
+
+// ----------------------------------------------------------------------------
+// local functions
+// ----------------------------------------------------------------------------
+
+// return the kind of transparency needed for this image assuming that it does
+// have transparent pixels, i.e. either Transparency_Alpha or Transparency_Mask
+static Transparency
+CheckTransparency(unsigned char **lines,
+                  png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h,
+                  size_t numColBytes);
+
+// init the alpha channel for the image and fill it with 1s up to (x, y)
+static unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y);
+
+// find a free colour for the mask in the PNG data array
+static void
+FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height,
+               unsigned char& rMask, unsigned char& gMask, unsigned char& bMask);
+
+// is the pixel with this value of alpha a fully opaque one?
+static inline
+bool IsOpaque(unsigned char a)
+{
+    return a == 0xff;
+}
+
+// is the pixel with this value of alpha a fully transparent one?
+static inline
+bool IsTransparent(unsigned char a)
+{
+    return !a;
+}
+
+// ============================================================================
+// wxPNGHandler implementation
+// ============================================================================

 
 

-#if !USE_SHARED_LIBRARIES

 IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler)
 IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler)

+
+#if wxUSE_STREAMS
+
+#ifndef PNGLINKAGEMODE
+    #ifdef __WATCOMC__
+        // we need an explicit cdecl for Watcom, at least according to
+        //
+        // http://sf.net/tracker/index.php?func=detail&aid=651492&group_id=9863&atid=109863
+        //
+        // more testing is needed for this however, please remove this comment
+        // if you can confirm that my fix works with Watcom 11
+        #define PNGLINKAGEMODE cdecl
+    #else
+        #define PNGLINKAGEMODE LINKAGEMODE
+    #endif

 #endif
 
 #endif
 

-#if wxUSE_LIBPNG

 
 

-#if defined(__VISAGECPP__)
-#define LINKAGEMODE _Optlink
-#else
-#define LINKAGEMODE
-#endif
+// VS: wxPNGInfoStruct declared below is a hack that needs some explanation.
+//     First, let me describe what's the problem: libpng uses jmp_buf in
+//     its png_struct structure. Unfortunately, this structure is
+//     compiler-specific and may vary in size, so if you use libpng compiled
+//     as DLL with another compiler than the main executable, it may not work
+//     (this is for example the case with wxMGL port and SciTech MGL library
+//     that provides custom runtime-loadable libpng implementation with jmpbuf
+//     disabled altogether). Luckily, it is still possible to use setjmp() &
+//     longjmp() as long as the structure is not part of png_struct.
+//
+//     Sadly, there's no clean way to attach user-defined data to png_struct.
+//     There is only one customizable place, png_struct.io_ptr, which is meant
+//     only for I/O routines and is set with png_set_read_fn or
+//     png_set_write_fn. The hacky part is that we use io_ptr to store
+//     a pointer to wxPNGInfoStruct that holds I/O structures _and_ jmp_buf.
+
+struct wxPNGInfoStruct
+{
+    jmp_buf jmpbuf;
+    bool verbose;
+
+    union
+    {
+        wxInputStream  *in;
+        wxOutputStream *out;
+    } stream;
+};

 
 

-static void LINKAGEMODE _PNG_stream_reader( png_structp png_ptr, png_bytep data, png_size_t length )
+#define WX_PNG_INFO(png_ptr) ((wxPNGInfoStruct*)png_get_io_ptr(png_ptr))
+
+// ----------------------------------------------------------------------------
+// helper functions
+// ----------------------------------------------------------------------------
+
+extern "C"

 {
 {

-    ((wxInputStream*) png_get_io_ptr( png_ptr )) -> Read(data, length);
+
+void PNGLINKAGEMODE wx_PNG_stream_reader( png_structp png_ptr, png_bytep data,
+                                          png_size_t length )
+{
+    WX_PNG_INFO(png_ptr)->stream.in->Read(data, length);

 }
 
 }
 

-static void LINKAGEMODE _PNG_stream_writer( png_structp png_ptr, png_bytep data, png_size_t length )
+void PNGLINKAGEMODE wx_PNG_stream_writer( png_structp png_ptr, png_bytep data,
+                                          png_size_t length )

 {
 {

-    ((wxOutputStream*) png_get_io_ptr( png_ptr )) -> Write(data, length);
+    WX_PNG_INFO(png_ptr)->stream.out->Write(data, length);

 }
 
 }
 

-// from pngerror.c
-// so that the libpng doesn't send anything on stderr

 void
 void

-LINKAGEMODE png_silent_error(png_structp png_ptr, png_const_charp WXUNUSED(message))
+PNGLINKAGEMODE wx_png_warning(png_structp png_ptr, png_const_charp message)

 {
 {

-#ifdef USE_FAR_KEYWORD
-   {
-      jmp_buf jmpbuf;
-      png_memcpy(jmpbuf,png_ptr->jmpbuf,sizeof(jmp_buf));
-      longjmp(jmpbuf, 1);
-   }
-#else
-   longjmp(png_ptr->jmpbuf, 1);
-#endif
+    wxPNGInfoStruct *info = png_ptr ? WX_PNG_INFO(png_ptr) : NULL;
+    if ( !info || info->verbose )
+        wxLogWarning( wxString::FromAscii(message) );

 }
 
 }
 

+// from pngerror.c
+// so that the libpng doesn't send anything on stderr

 void
 void

-LINKAGEMODE png_silent_warning(png_structp WXUNUSED(png_ptr), png_const_charp WXUNUSED(message))
+PNGLINKAGEMODE wx_png_error(png_structp png_ptr, png_const_charp message)

 {
 {

+    wx_png_warning(NULL, message);
+
+    // we're not using libpng built-in jump buffer (see comment before
+    // wxPNGInfoStruct above) so we have to return ourselves, otherwise libpng
+    // would just abort
+    longjmp(WX_PNG_INFO(png_ptr)->jmpbuf, 1);

 }
 
 }
 

-bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose)
+} // extern "C"
+
+// ----------------------------------------------------------------------------
+// LoadFile() helpers
+// ----------------------------------------------------------------------------
+
+// determine the kind of transparency we need for this image: if the only alpha
+// values it has are 0 (transparent) and 0xff (opaque) then we can simply
+// create a mask for it, we should be ok with a simple mask but otherwise we
+// need a full blown alpha channel in wxImage
+//
+// parameters:
+//      lines           raw PNG data
+//      x, y            starting position
+//      w, h            size of the image
+//      numColBytes     number of colour bytes (1 for grey scale, 3 for RGB)
+//                      (NB: alpha always follows the colour bytes)
+Transparency
+CheckTransparency(unsigned char **lines,
+                  png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h,
+                  size_t numColBytes)

 {
 {

-    // VZ: as this function uses setjmp() the only fool proof error handling
-    //     method is to use goto (setjmp is not really C++ dtors friendly...)
+    // suppose that a mask will suffice and check all the remaining alpha
+    // values to see if it does
+    for ( ; y < h; y++ )
+    {
+        // each pixel is numColBytes+1 bytes, offset into the current line by
+        // the current x position
+        unsigned const char *ptr = lines[y] + (x * (numColBytes + 1));

 
 

-    unsigned char **lines;
-    unsigned int i;
-    png_infop info_ptr = (png_infop) NULL;
+        for ( png_uint_32 x2 = x; x2 < w; x2++ )
+        {
+            // skip the grey or colour byte(s)
+            ptr += numColBytes;

 
 

-    image->Destroy();
+            unsigned char a2 = *ptr++;

 
 

-    png_structp png_ptr = png_create_read_struct( PNG_LIBPNG_VER_STRING,
-        (voidp) NULL,
-        (png_error_ptr) NULL,
-        (png_error_ptr) NULL );
-    if (!png_ptr)
-        goto error_nolines;
+            if ( !IsTransparent(a2) && !IsOpaque(a2) )
+            {
+                // not fully opaque nor fully transparent, hence need alpha
+                return Transparency_Alpha;
+            }
+        }

 
 

-    // the file example.c explain how to guess if the stream is a png image
-    if (!verbose) png_set_error_fn(png_ptr, (png_voidp)NULL, png_silent_error, png_silent_warning);
+        // during the next loop iteration check all the pixels in the row
+        x = 0;
+    }

 
 

-    info_ptr = png_create_info_struct( png_ptr );
-    if (!info_ptr)
-        goto error_nolines;
+    // mask will be enough
+    return Transparency_Mask;
+}

 
 

-    if (setjmp(png_ptr->jmpbuf))
-        goto error_nolines;
+unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y)
+{
+    // create alpha channel
+    image->SetAlpha();

 
 

-    if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-        goto error_nolines;
+    unsigned char *alpha = image->GetAlpha();

 
 

-    png_set_read_fn( png_ptr, &stream, _PNG_stream_reader);
+    // set alpha for the pixels we had so far
+    png_uint_32 end = y * image->GetWidth() + x;
+    for ( png_uint_32 i = 0; i < end; i++ )
+    {
+        // all the previous pixels were opaque
+        *alpha++ = 0xff;
+    }

 
 

-    png_uint_32 width,height;
-    int bit_depth,color_type,interlace_type;
+    return alpha;
+}

 
 

-    png_read_info( png_ptr, info_ptr );
-    png_get_IHDR( png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, (int*) NULL, (int*) NULL );
+void
+FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height,
+               unsigned char& rMask, unsigned char& gMask, unsigned char& bMask)
+{
+    // choosing the colour for the mask is more
+    // difficult: we need to iterate over the entire
+    // image for this in order to choose an unused
+    // colour (this is not very efficient but what else
+    // can we do?)
+    wxImageHistogram h;
+    unsigned nentries = 0;
+    unsigned char r2, g2, b2;
+    for ( png_uint_32 y2 = 0; y2 < height; y2++ )
+    {
+        const unsigned char *p = lines[y2];
+        for ( png_uint_32 x2 = 0; x2 < width; x2++ )
+        {
+            r2 = *p++;
+            g2 = *p++;
+            b2 = *p++;
+            ++p; // jump over alpha

 
 

-    if (color_type == PNG_COLOR_TYPE_PALETTE)
-        png_set_expand( png_ptr );
+            wxImageHistogramEntry&
+                entry = h[wxImageHistogram:: MakeKey(r2, g2, b2)];

 
 

-    png_set_strip_16( png_ptr );
-    png_set_packing( png_ptr );
-    if (png_get_valid( png_ptr, info_ptr, PNG_INFO_tRNS))
-        png_set_expand( png_ptr );
-    png_set_filler( png_ptr, 0xff, PNG_FILLER_AFTER );
+            if ( entry.value++ == 0 )
+                entry.index = nentries++;
+        }
+    }
+
+    if ( !h.FindFirstUnusedColour(&rMask, &gMask, &bMask) )
+    {
+        wxLogWarning(_("Too many colours in PNG, the image may be slightly blurred."));
+
+        // use a fixed mask colour and we'll fudge
+        // the real pixels with this colour (see
+        // below)
+        rMask = 0xfe;
+        gMask = 0;
+        bMask = 0xff;
+    }
+}

 
 

-    image->Create( width, height );
+// ----------------------------------------------------------------------------
+// reading PNGs
+// ----------------------------------------------------------------------------

 
 

-    if (!image->Ok())
-        goto error_nolines;
+bool wxPNGHandler::DoCanRead( wxInputStream& stream )
+{
+    unsigned char hdr[4];

 
 

-    lines = (unsigned char **)malloc( height * sizeof(unsigned char *) );
-    if (lines == NULL)
-        goto error_nolines;
+    if ( !stream.Read(hdr, WXSIZEOF(hdr)) )
+        return false;

 
 

-    for (i = 0; i < height; i++)
-    {
-        if ((lines[i] = (unsigned char *)malloc(width * (sizeof(unsigned char) * 4))) == NULL)
-        {
-            for ( unsigned int n = 0; n < i; n++ )
-                free( lines[n] );
-            goto error;
-        }
-    }
+    return memcmp(hdr, "\211PNG", WXSIZEOF(hdr)) == 0;
+}

 
 

-    // loaded successfully!
+// convert data from RGB to wxImage format
+static
+void CopyDataFromPNG(wxImage *image,
+                     unsigned char **lines,
+                     png_uint_32 width,
+                     png_uint_32 height,
+                     int color_type)
+{
+    Transparency transparency = Transparency_None;
+
+    // only non NULL if transparency == Transparency_Alpha
+    unsigned char *alpha = NULL;
+
+    // RGB of the mask colour if transparency == Transparency_Mask
+    // (but init them anyhow to avoid compiler warnings)
+    unsigned char rMask = 0,
+                  gMask = 0,
+                  bMask = 0;
+
+    unsigned char *ptrDst = image->GetData();
+    if ( !(color_type & PNG_COLOR_MASK_COLOR) )

     {
     {

-        int transp = 0;
-        png_read_image( png_ptr, lines );
-        png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL );
-        unsigned char *ptr = image->GetData();
-        if ((color_type == PNG_COLOR_TYPE_GRAY) ||
-            (color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+        // grey image: GAGAGA... where G == grey component and A == alpha
+        for ( png_uint_32 y = 0; y < height; y++ )

         {
         {

-            for (unsigned int y = 0; y < height; y++)
+            const unsigned char *ptrSrc = lines[y];
+            for ( png_uint_32 x = 0; x < width; x++ )

             {
             {

-                unsigned char *ptr2 = lines[y];
-                for (unsigned int x = 0; x < width; x++)
+                unsigned char g = *ptrSrc++;
+                unsigned char a = *ptrSrc++;
+
+                // the first time we encounter a transparent pixel we must
+                // decide about what to do about them
+                if ( !IsOpaque(a) && transparency == Transparency_None )

                 {
                 {

-                    unsigned char r = *ptr2++;
-                    unsigned char a = *ptr2++;
-                    if (a < 128)
+                    // we'll need at least the mask for this image and
+                    // maybe even full alpha channel info: the former is
+                    // only enough if we have alpha values of 0 and 0xff
+                    // only, otherwisewe need the latter
+                    transparency = CheckTransparency
+                                   (
+                                        lines,
+                                        x, y,
+                                        width, height,
+                                        1
+                                   );
+
+                    if ( transparency == Transparency_Mask )

                     {
                     {

-                        *ptr++ = 255;
-                        *ptr++ = 0;
-                        *ptr++ = 255;
-                        transp = 1;
+                        // let's choose this colour for the mask: this is
+                        // not a problem here as all the other pixels are
+                        // grey, i.e. R == G == B which is not the case for
+                        // this one so no confusion is possible
+                        rMask = 0xff;
+                        gMask = 0;
+                        bMask = 0xff;

                     }
                     }

-                    else
+                    else // transparency == Transparency_Alpha

                     {
                     {

-                        *ptr++ = r;
-                        *ptr++ = r;
-                        *ptr++ = r;
+                        alpha = InitAlpha(image, x, y);

                     }
                 }
                     }
                 }

+
+                switch ( transparency )
+                {
+                    case Transparency_Mask:
+                        if ( IsTransparent(a) )
+                        {
+                            *ptrDst++ = rMask;
+                            *ptrDst++ = gMask;
+                            *ptrDst++ = bMask;
+                            break;
+                        }
+                        // else: !transparent
+
+                        // must be opaque then as otherwise we shouldn't be
+                        // using the mask at all
+                        wxASSERT_MSG( IsOpaque(a), _T("logic error") );
+
+                        // fall through
+
+                    case Transparency_Alpha:
+                        if ( alpha )
+                            *alpha++ = a;
+                        // fall through
+
+                    case Transparency_None:
+                        *ptrDst++ = g;
+                        *ptrDst++ = g;
+                        *ptrDst++ = g;
+                        break;
+                }

             }
         }
             }
         }

-        else
+    }
+    else // colour image: RGBRGB...
+    {
+        for ( png_uint_32 y = 0; y < height; y++ )

         {
         {

-            for (unsigned int y = 0; y < height; y++)
+            const unsigned char *ptrSrc = lines[y];
+            for ( png_uint_32 x = 0; x < width; x++ )

             {
             {

-                unsigned char *ptr2 = lines[y];
-                for (unsigned int x = 0; x < width; x++)
+                unsigned char r = *ptrSrc++;
+                unsigned char g = *ptrSrc++;
+                unsigned char b = *ptrSrc++;
+                unsigned char a = *ptrSrc++;
+
+                // the logic here is the same as for the grey case except
+                // where noted
+                if ( !IsOpaque(a) && transparency == Transparency_None )

                 {
                 {

-                    unsigned char r = *ptr2++;
-                    unsigned char g = *ptr2++;
-                    unsigned char b = *ptr2++;
-                    unsigned char a = *ptr2++;
-                    if (a < 128)
+                    transparency = CheckTransparency
+                                   (
+                                        lines,
+                                        x, y,
+                                        width, height,
+                                        3
+                                   );
+
+                    if ( transparency == Transparency_Mask )

                     {
                     {

-                        *ptr++ = 255;
-                        *ptr++ = 0;
-                        *ptr++ = 255;
-                        transp = 1;
+                        FindMaskColour(lines, width, height,
+                                       rMask, gMask, bMask);

                     }
                     }

-                    else
+                    else // transparency == Transparency_Alpha

                     {
                     {

-                        if ((r == 255) && (g == 0) && (b == 255)) r = 254;
-                        *ptr++ = r;
-                        *ptr++ = g;
-                        *ptr++ = b;
+                        alpha = InitAlpha(image, x, y);

                     }
                     }

+
+                }
+
+                switch ( transparency )
+                {
+                    case Transparency_Mask:
+                        if ( IsTransparent(a) )
+                        {
+                            *ptrDst++ = rMask;
+                            *ptrDst++ = gMask;
+                            *ptrDst++ = bMask;
+                            break;
+                        }
+                        else // !transparent
+                        {
+                            // must be opaque then as otherwise we shouldn't be
+                            // using the mask at all
+                            wxASSERT_MSG( IsOpaque(a), _T("logic error") );
+
+                            // if we couldn't find a unique colour for the
+                            // mask, we can have real pixels with the same
+                            // value as the mask and it's better to slightly
+                            // change their colour than to make them
+                            // transparent
+                            if ( r == rMask && g == gMask && b == bMask )
+                            {
+                                r++;
+                            }
+                        }
+
+                        // fall through
+
+                    case Transparency_Alpha:
+                        if ( alpha )
+                            *alpha++ = a;
+                        // fall through
+
+                    case Transparency_None:
+                        *ptrDst++ = r;
+                        *ptrDst++ = g;
+                        *ptrDst++ = b;
+                        break;

                 }
             }
         }
                 }
             }
         }

+    }

 
 

-        for ( unsigned int j = 0; j < height; j++ )
-            free( lines[j] );
-        free( lines );
+    if ( transparency == Transparency_Mask )
+    {
+        image->SetMaskColour(rMask, gMask, bMask);
+    }
+}
+
+// temporarily disable the warning C4611 (interaction between '_setjmp' and
+// C++ object destruction is non-portable) - I don't see any dtors here
+#ifdef __VISUALC__
+    #pragma warning(disable:4611)
+#endif /* VC++ */
+
+bool
+wxPNGHandler::LoadFile(wxImage *image,
+                       wxInputStream& stream,
+                       bool verbose,
+                       int WXUNUSED(index))
+{
+    // VZ: as this function uses setjmp() the only fool-proof error handling
+    //     method is to use goto (setjmp is not really C++ dtors friendly...)
+
+    unsigned char **lines = NULL;
+    png_infop info_ptr = (png_infop) NULL;
+    wxPNGInfoStruct wxinfo;
+
+    png_uint_32 i, width, height = 0;
+    int bit_depth, color_type, interlace_type;

 
 

-        if (transp)
+    wxinfo.verbose = verbose;
+    wxinfo.stream.in = &stream;
+
+    image->Destroy();
+
+    png_structp png_ptr = png_create_read_struct
+                          (
+                            PNG_LIBPNG_VER_STRING,
+                            (voidp) NULL,
+                            wx_png_error,
+                            wx_png_warning
+                          );
+    if (!png_ptr)
+        goto error;
+
+    // NB: please see the comment near wxPNGInfoStruct declaration for
+    //     explanation why this line is mandatory
+    png_set_read_fn( png_ptr, &wxinfo, wx_PNG_stream_reader);
+
+    info_ptr = png_create_info_struct( png_ptr );
+    if (!info_ptr)
+        goto error;
+
+    if (setjmp(wxinfo.jmpbuf))
+        goto error;
+
+    png_read_info( png_ptr, info_ptr );
+    png_get_IHDR( png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, (int*) NULL, (int*) NULL );
+
+    if (color_type == PNG_COLOR_TYPE_PALETTE)
+        png_set_expand( png_ptr );
+
+    // Fix for Bug [ 439207 ] Monochrome PNG images come up black
+    if (bit_depth < 8)
+        png_set_expand( png_ptr );
+
+    png_set_strip_16( png_ptr );
+    png_set_packing( png_ptr );
+    if (png_get_valid( png_ptr, info_ptr, PNG_INFO_tRNS))
+        png_set_expand( png_ptr );
+    png_set_filler( png_ptr, 0xff, PNG_FILLER_AFTER );
+
+    image->Create((int)width, (int)height, (bool) false /* no need to init pixels */);
+
+    if (!image->Ok())
+        goto error;
+
+    lines = (unsigned char **)malloc( (size_t)(height * sizeof(unsigned char *)) );
+    if ( !lines )
+        goto error;
+
+    for (i = 0; i < height; i++)
+    {
+        if ((lines[i] = (unsigned char *)malloc( (size_t)(width * (sizeof(unsigned char) * 4)))) == NULL)

         {
         {

-            image->SetMaskColour( 255, 0, 255 );
+            for ( unsigned int n = 0; n < i; n++ )
+                free( lines[n] );
+            goto error;

         }
         }

-        else
+    }
+
+    png_read_image( png_ptr, lines );
+    png_read_end( png_ptr, info_ptr );
+
+#if wxUSE_PALETTE
+    if (color_type == PNG_COLOR_TYPE_PALETTE)
+    {
+        const size_t ncolors = info_ptr->num_palette;
+        unsigned char* r = new unsigned char[ncolors];
+        unsigned char* g = new unsigned char[ncolors];
+        unsigned char* b = new unsigned char[ncolors];
+
+        for (size_t j = 0; j < ncolors; j++)

         {
         {

-            image->SetMask( FALSE );
+            r[j] = info_ptr->palette[j].red;
+            g[j] = info_ptr->palette[j].green;
+            b[j] = info_ptr->palette[j].blue;

         }
         }

+
+        image->SetPalette(wxPalette(ncolors, r, g, b));
+        delete[] r;
+        delete[] g;
+        delete[] b;

     }
     }

+#endif // wxUSE_PALETTE
+
+    png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL );

 
 

-    return TRUE;
+    // loaded successfully, now init wxImage with this data
+    CopyDataFromPNG(image, lines, width, height, color_type);

 
 

- error_nolines:
-    lines = NULL; // called from before it was set
- error:
-    wxLogError(_("Couldn't load a PNG image - probably file is corrupted."));
+    for ( i = 0; i < height; i++ )
+        free( lines[i] );
+    free( lines );
+
+    return true;
+
+error:
+    if (verbose)
+       wxLogError(_("Couldn't load a PNG image - file is corrupted or not enough memory."));

 
     if ( image->Ok() )
     {
 
     if ( image->Ok() )
     {


@@ -252,6 +627,9 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
 
     if ( lines )
     {
 
     if ( lines )
     {

+        for ( unsigned int n = 0; n < height; n++ )
+            free( lines[n] );
+

         free( lines );
     }
 
         free( lines );
     }
 


@@ -265,97 +643,224 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
         else
             png_destroy_read_struct( &png_ptr, (png_infopp) NULL, (png_infopp) NULL );
     }
         else
             png_destroy_read_struct( &png_ptr, (png_infopp) NULL, (png_infopp) NULL );
     }

-    return FALSE;
+    return false;

 }
 
 }
 

+// ----------------------------------------------------------------------------
+// writing PNGs
+// ----------------------------------------------------------------------------

 
 bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 {
 
 bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 {

+    wxPNGInfoStruct wxinfo;
+
+    wxinfo.verbose = verbose;
+    wxinfo.stream.out = &stream;
+
+    png_structp png_ptr = png_create_write_struct
+                          (
+                            PNG_LIBPNG_VER_STRING,
+                            NULL,
+                            wx_png_error,
+                            wx_png_warning
+                          );
+    if (!png_ptr)

     {
     {

-        png_structp png_ptr = png_create_write_struct( PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-        if (!png_ptr)
-        {
-            return FALSE;
-        }
+        if (verbose)
+           wxLogError(_("Couldn't save PNG image."));
+        return false;
+    }
+
+    png_infop info_ptr = png_create_info_struct(png_ptr);
+    if (info_ptr == NULL)
+    {
+        png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
+        if (verbose)
+           wxLogError(_("Couldn't save PNG image."));
+        return false;
+    }

 
 

-        if (!verbose) png_set_error_fn(png_ptr, (png_voidp)NULL, png_silent_error, png_silent_warning);
+    if (setjmp(wxinfo.jmpbuf))
+    {
+        png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
+        if (verbose)
+           wxLogError(_("Couldn't save PNG image."));
+        return false;
+    }

 
 

-        png_infop info_ptr = png_create_info_struct(png_ptr);
-        if (info_ptr == NULL)
-        {
-            png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
-            return FALSE;
-        }
+    // NB: please see the comment near wxPNGInfoStruct declaration for
+    //     explanation why this line is mandatory
+    png_set_write_fn( png_ptr, &wxinfo, wx_PNG_stream_writer, NULL);

 
 

-        if (setjmp(png_ptr->jmpbuf))
-        {
-            png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
-            return FALSE;
-        }
+    const int iColorType = image->HasOption(wxIMAGE_OPTION_PNG_FORMAT)
+                            ? image->GetOptionInt(wxIMAGE_OPTION_PNG_FORMAT)
+                            : wxPNG_TYPE_COLOUR;
+    const int iBitDepth = image->HasOption(wxIMAGE_OPTION_PNG_BITDEPTH)
+                            ? image->GetOptionInt(wxIMAGE_OPTION_PNG_BITDEPTH)
+                            : 8;

 
 

-        png_set_write_fn( png_ptr, &stream, _PNG_stream_writer, NULL);
+    wxASSERT_MSG( iBitDepth == 8 || iBitDepth == 16,
+                    _T("PNG bit depth must be 8 or 16") );

 
 

-        png_set_IHDR( png_ptr, info_ptr, image->GetWidth(), image->GetHeight(), 8,
-            PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
-            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+    bool bHasAlpha = image->HasAlpha();
+    bool bHasMask = image->HasMask();
+    bool bUseAlpha = bHasAlpha || bHasMask;

 
 

-        png_color_8 sig_bit;
-        sig_bit.red = 8;
-        sig_bit.green = 8;
-        sig_bit.blue = 8;
-        sig_bit.alpha = 8;
-        png_set_sBIT( png_ptr, info_ptr, &sig_bit );
-        png_write_info( png_ptr, info_ptr );
-        png_set_shift( png_ptr, &sig_bit );
-        png_set_packing( png_ptr );
+    int iPngColorType;
+    if ( iColorType==wxPNG_TYPE_COLOUR )
+    {
+        iPngColorType = bUseAlpha ? PNG_COLOR_TYPE_RGB_ALPHA
+                                  : PNG_COLOR_TYPE_RGB;
+    }
+    else
+    {
+        iPngColorType = bUseAlpha ? PNG_COLOR_TYPE_GRAY_ALPHA
+                                  : PNG_COLOR_TYPE_GRAY;
+    }

 
 

-        unsigned char *data = (unsigned char *)malloc( image->GetWidth()*4 );
-        if (!data)
-        {
-            png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
-            return FALSE;
-        }
+    png_set_IHDR( png_ptr, info_ptr, image->GetWidth(), image->GetHeight(),
+                  iBitDepth, iPngColorType,
+                  PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
+                  PNG_FILTER_TYPE_BASE);

 
 

-        for (int y = 0; y < image->GetHeight(); y++)
+    int iElements;
+    png_color_8 sig_bit;
+
+    if ( iPngColorType & PNG_COLOR_MASK_COLOR )
+    {
+        sig_bit.red =
+        sig_bit.green =
+        sig_bit.blue = (png_byte)iBitDepth;
+        iElements = 3;
+    }
+    else // grey
+    {
+        sig_bit.gray = (png_byte)iBitDepth;
+        iElements = 1;
+    }
+
+    if ( iPngColorType & PNG_COLOR_MASK_ALPHA )
+    {
+        sig_bit.alpha = (png_byte)iBitDepth;
+        iElements++;
+    }
+
+    if ( iBitDepth == 16 )
+        iElements *= 2;
+
+    png_set_sBIT( png_ptr, info_ptr, &sig_bit );
+    png_write_info( png_ptr, info_ptr );
+    png_set_shift( png_ptr, &sig_bit );
+    png_set_packing( png_ptr );
+
+    unsigned char *
+        data = (unsigned char *)malloc( image->GetWidth() * iElements );
+    if ( !data )
+    {
+        png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
+        return false;
+    }
+
+    unsigned char *
+        pAlpha = (unsigned char *)(bHasAlpha ? image->GetAlpha() : NULL);
+    int iHeight = image->GetHeight();
+    int iWidth = image->GetWidth();
+
+    unsigned char uchMaskRed = 0, uchMaskGreen = 0, uchMaskBlue = 0;
+
+    if ( bHasMask )
+    {
+        uchMaskRed = image->GetMaskRed();
+        uchMaskGreen = image->GetMaskGreen();
+        uchMaskBlue = image->GetMaskBlue();
+    }
+
+    unsigned char *pColors = image->GetData();
+
+    for (int y = 0; y != iHeight; ++y)
+    {
+        unsigned char *pData = data;
+        for (int x = 0; x != iWidth; x++)

         {
         {

-            unsigned char *ptr = image->GetData() + (y * image->GetWidth() * 3);
-            for (int x = 0; x < image->GetWidth(); x++)
+            unsigned char uchRed = *pColors++;
+            unsigned char uchGreen = *pColors++;
+            unsigned char uchBlue = *pColors++;
+
+            switch ( iColorType )

             {
             {

-                data[(x << 2) + 0] = *ptr++;
-                data[(x << 2) + 1] = *ptr++;
-                data[(x << 2) + 2] = *ptr++;
-                if (( !image->HasMask() ) || \
-                    (data[(x << 2) + 0] != image->GetMaskRed()) || \
-                    (data[(x << 2) + 1] != image->GetMaskGreen()) || \
-                    (data[(x << 2) + 2] != image->GetMaskBlue()))
-                {
-                    data[(x << 2) + 3] = 255;
-                }
-                else
+                default:
+                    wxFAIL_MSG( _T("unknown wxPNG_TYPE_XXX") );
+                    // fall through
+
+                case wxPNG_TYPE_COLOUR:
+                    *pData++ = uchRed;
+                    if ( iBitDepth == 16 )
+                        *pData++ = 0;
+                    *pData++ = uchGreen;
+                    if ( iBitDepth == 16 )
+                        *pData++ = 0;
+                    *pData++ = uchBlue;
+                    if ( iBitDepth == 16 )
+                        *pData++ = 0;
+                    break;
+
+                case wxPNG_TYPE_GREY:
+                    {
+                        // where do these coefficients come from? maybe we
+                        // should have image options for them as well?
+                        unsigned uiColor =
+                            (unsigned) (76.544*(unsigned)uchRed +
+                                        150.272*(unsigned)uchGreen +
+                                        36.864*(unsigned)uchBlue);
+
+                        *pData++ = (unsigned char)((uiColor >> 8) & 0xFF);
+                        if ( iBitDepth == 16 )
+                            *pData++ = (unsigned char)(uiColor & 0xFF);
+                    }
+                    break;
+
+                case wxPNG_TYPE_GREY_RED:
+                    *pData++ = uchRed;
+                    if ( iBitDepth == 16 )
+                        *pData++ = 0;
+                    break;
+            }
+
+            if ( bUseAlpha )
+            {
+                unsigned char uchAlpha = 255;
+                if ( bHasAlpha )
+                    uchAlpha = *pAlpha++;
+
+                if ( bHasMask )

                 {
                 {

-                    data[(x << 2) + 3] = 0;
+                    if ( (uchRed == uchMaskRed)
+                            && (uchGreen == uchMaskGreen)
+                                && (uchBlue == uchMaskBlue) )
+                        uchAlpha = 0;

                 }
                 }

+
+                *pData++ = uchAlpha;
+                if ( iBitDepth == 16 )
+                    *pData++ = 0;

             }
             }

-            png_bytep row_ptr = data;
-            png_write_rows( png_ptr, &row_ptr, 1 );

         }
 
         }
 

-        free(data);
-        png_write_end( png_ptr, info_ptr );
-        png_destroy_write_struct( &png_ptr, (png_infopp)&info_ptr );
+        png_bytep row_ptr = data;
+        png_write_rows( png_ptr, &row_ptr, 1 );

     }
     }

-    return TRUE;
-}

 
 

-bool wxPNGHandler::DoCanRead( wxInputStream& stream )
-{
-    unsigned char hdr[4];
+    free(data);
+    png_write_end( png_ptr, info_ptr );
+    png_destroy_write_struct( &png_ptr, (png_infopp)&info_ptr );

 
 

-    stream.Read(&hdr, 4);
-    stream.SeekI(-4, wxFromCurrent);
-    return (hdr[0] == 0x89 && hdr[1] == 'P' && hdr[2] == 'N' && hdr[3] == 'G');
+    return true;

 }
 
 }
 

+#ifdef __VISUALC__
+    #pragma warning(default:4611)
+#endif /* VC++ */
+

 #endif  // wxUSE_STREAMS
 
 #endif  // wxUSE_LIBPNG
 #endif  // wxUSE_STREAMS
 
 #endif  // wxUSE_LIBPNG