added support for reading alpha channel
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19456 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
parent
487659e0fa
commit
27bb2b7cea
@ -1,5 +1,5 @@
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/////////////////////////////////////////////////////////////////////////////
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// Name: imagepng.cpp
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// Name: src/common/imagepng.cpp
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// Purpose: wxImage PNG handler
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// Author: Robert Roebling
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// RCS-ID: $Id$
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@ -7,10 +7,18 @@
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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// ============================================================================
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// declarations
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// ============================================================================
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#ifdef __GNUG__
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#pragma implementation "imagpng.h"
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#endif
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// ----------------------------------------------------------------------------
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// headers
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// ----------------------------------------------------------------------------
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// For compilers that support precompilation, includes "wx.h".
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#include "wx/wxprec.h"
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@ -44,13 +52,42 @@
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#endif
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#endif
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#ifdef __WXMSW__
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#include <windows.h>
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#endif
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// ----------------------------------------------------------------------------
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// constants
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// ----------------------------------------------------------------------------
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//-----------------------------------------------------------------------------
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// wxPNGHandler
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//-----------------------------------------------------------------------------
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// image can not have any transparent pixels at all, have only 100% opaque
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// and/or 100% transparent pixels in which case a simple mask is enough to
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// store this information in wxImage or have a real alpha channel in which case
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// we need to have it in wxImage as well
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enum Transparency
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{
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Transparency_None,
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Transparency_Mask,
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Transparency_Alpha
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};
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// ----------------------------------------------------------------------------
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// local functions
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// ----------------------------------------------------------------------------
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// return the kind of transparency needed for this image assuming that it does
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// have transparent pixels, i.e. either Transparency_Alpha or Transparency_Mask
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static Transparency
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CheckTransparency(const unsigned char *ptr,
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png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h);
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// init the alpha channel for the image and fill it with 1s up to (x, y)
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static unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y);
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// find a free colour for the mask in the PNG data array
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static void
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FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height,
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unsigned char& rMask, unsigned char& gMask, unsigned char& bMask);
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// ============================================================================
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// wxPNGHandler implementation
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// ============================================================================
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IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler)
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@ -72,18 +109,18 @@ IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler)
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// VS: wxPNGInfoStruct declared below is a hack that needs some explanation.
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// First, let me describe what's the problem: libpng uses jmp_buf in
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// its png_struct structure. Unfortunately, this structure is
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// compiler-specific and may vary in size, so if you use libpng compiled
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// First, let me describe what's the problem: libpng uses jmp_buf in
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// its png_struct structure. Unfortunately, this structure is
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// compiler-specific and may vary in size, so if you use libpng compiled
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// as DLL with another compiler than the main executable, it may not work
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// (this is for example the case with wxMGL port and SciTech MGL library
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// (this is for example the case with wxMGL port and SciTech MGL library
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// that provides custom runtime-loadable libpng implementation with jmpbuf
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// disabled altogether). Luckily, it is still possible to use setjmp() &
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// disabled altogether). Luckily, it is still possible to use setjmp() &
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// longjmp() as long as the structure is not part of png_struct.
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//
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// Sadly, there's no clean way to attach user-defined data to png_struct.
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// There is only one customizable place, png_struct.io_ptr, which is meant
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// only for I/O routines and is set with png_set_read_fn or
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// only for I/O routines and is set with png_set_read_fn or
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// png_set_write_fn. The hacky part is that we use io_ptr to store
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// a pointer to wxPNGInfoStruct that holds I/O structures _and_ jmp_buf.
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@ -91,7 +128,7 @@ struct wxPNGInfoStruct
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{
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jmp_buf jmpbuf;
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bool verbose;
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union
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{
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wxInputStream *in;
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@ -101,6 +138,9 @@ struct wxPNGInfoStruct
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#define WX_PNG_INFO(png_ptr) ((wxPNGInfoStruct*)png_get_io_ptr(png_ptr))
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// ----------------------------------------------------------------------------
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// helper functions
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// ----------------------------------------------------------------------------
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extern "C"
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{
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@ -145,20 +185,285 @@ PNGLINKAGEMODE wx_png_warning(png_structp png_ptr, png_const_charp message)
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} // extern "C"
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// ----------------------------------------------------------------------------
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// LoadFile() helpers
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// ----------------------------------------------------------------------------
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Transparency
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CheckTransparency(const unsigned char *ptr,
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png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h)
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{
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// suppose that a mask will suffice
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Transparency transparency = Transparency_Mask;
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// and check all the remaining alpha values to see if it does
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unsigned char a2;
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unsigned const char *ptr2 = ptr;
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for ( png_uint_32 y2 = y; y2 < h; y2++ )
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{
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for ( png_uint_32 x2 = x + 1; x2 < w; x2++ )
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{
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// skip the grey byte
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a2 = *++ptr2;
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if ( a2 && a2 != 0xff )
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{
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// not fully opeaque nor fully transparent, hence need alpha
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transparency = Transparency_Alpha;
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break;
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}
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++ptr2;
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}
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if ( transparency == Transparency_Alpha )
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{
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// no need to continue
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break;
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}
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}
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return transparency;
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}
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unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y)
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{
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// create alpha channel
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image->SetAlpha();
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unsigned char *alpha = image->GetAlpha();
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// set alpha for the pixels we had so far
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for ( png_uint_32 y2 = 0; y2 <= y; y2++ )
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{
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for ( png_uint_32 x2 = 0; x2 < x; x2++ )
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{
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// all the previous pixels were opaque
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*alpha++ = 0xff;
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}
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}
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return alpha;
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}
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void
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FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height,
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unsigned char& rMask, unsigned char& gMask, unsigned char& bMask)
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{
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// choosing the colour for the mask is more
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// difficult: we need to iterate over the entire
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// image for this in order to choose an unused
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// colour (this is not very efficient but what else
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// can we do?)
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wxImageHistogram h;
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unsigned nentries = 0;
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unsigned char r2, g2, b2;
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for ( png_uint_32 y2 = 0; y2 < height; y2++ )
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{
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const unsigned char *p = lines[y2];
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for ( png_uint_32 x2 = 0; x2 < width; x2++ )
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{
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r2 = *p++;
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g2 = *p++;
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b2 = *p++;
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wxImageHistogramEntry&
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entry = h[wxImageHistogram:: MakeKey(r2, g2, b2)];
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if ( entry.value++ == 0 )
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entry.index = nentries++;
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}
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}
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if ( !h.FindFirstUnusedColour(&rMask, &gMask, &bMask) )
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{
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wxLogWarning(_("Too many colours in PNG, the image may be slightly blurred."));
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// use a fixed mask colour and we'll fudge
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// the real pixels with this colour (see
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// below)
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rMask = 0xfe;
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gMask = 0;
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bMask = 0xff;
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}
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}
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// ----------------------------------------------------------------------------
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// reading PNGs
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// ----------------------------------------------------------------------------
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bool wxPNGHandler::DoCanRead( wxInputStream& stream )
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{
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unsigned char hdr[4];
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if ( !stream.Read(hdr, WXSIZEOF(hdr)) )
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return FALSE;
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return memcmp(hdr, "\211PNG", WXSIZEOF(hdr)) == 0;
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}
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// convert data from RGB to wxImage format
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static
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void CopyDataFromPNG(wxImage *image,
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unsigned char **lines,
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png_uint_32 width,
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png_uint_32 height,
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int color_type)
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{
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Transparency transparency = Transparency_None;
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// only non NULL if transparency == Transparency_Alpha
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unsigned char *alpha = NULL;
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// RGB of the mask colour if transparency == Transparency_Mask
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// (but init them anyhow to avoid compiler warnings)
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unsigned char rMask = 0,
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gMask = 0,
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bMask = 0;
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unsigned char *ptrDst = image->GetData();
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if ( !(color_type & PNG_COLOR_MASK_COLOR) )
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{
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// grey image: GAGAGA... where G == grey component and A == alpha
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for ( png_uint_32 y = 0; y < height; y++ )
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{
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const unsigned char *ptrSrc = lines[y];
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for ( png_uint_32 x = 0; x < width; x++ )
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{
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unsigned char g = *ptrSrc++;
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unsigned char a = *ptrSrc++;
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// the first time we encounter a transparent pixel we must
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// decide about what to do about them
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if ( a != 0xff && transparency == Transparency_None )
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{
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// we'll need at least the mask for this image and
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// maybe even full alpha channel info: the former is
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// only enough if we have alpha values of 0 and 0xff
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// only, otherwisewe need the latter
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transparency = CheckTransparency(ptrSrc, x, y,
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width, height);
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if ( transparency == Transparency_Mask )
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{
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// let's choose this colour for the mask: this is
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// not a problem here as all the other pixels are
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// grey, i.e. R == G == B which is not the case for
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// this one so no confusion is possible
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rMask = 0xff;
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gMask = 0;
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bMask = 0xff;
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}
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else // transparency == Transparency_Alpha
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{
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alpha = InitAlpha(image, x, y);
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}
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}
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switch ( transparency )
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{
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case Transparency_Alpha:
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*alpha++ = a;
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// fall through
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case Transparency_None:
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*ptrDst++ = g;
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*ptrDst++ = g;
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*ptrDst++ = g;
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break;
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case Transparency_Mask:
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*ptrDst++ = rMask;
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*ptrDst++ = bMask;
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*ptrDst++ = gMask;
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}
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}
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}
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}
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else // colour image: RGBRGB...
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{
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for ( png_uint_32 y = 0; y < height; y++ )
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{
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const unsigned char *ptrSrc = lines[y];
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for ( png_uint_32 x = 0; x < width; x++ )
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{
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unsigned char r = *ptrSrc++;
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unsigned char g = *ptrSrc++;
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unsigned char b = *ptrSrc++;
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unsigned char a = *ptrSrc++;
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// the logic here is the same as for the grey case except
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// where noted
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if ( a != 0xff && transparency == Transparency_None )
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{
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transparency = CheckTransparency(ptrSrc, x, y,
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width, height);
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if ( transparency == Transparency_Mask )
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{
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FindMaskColour(lines, width, height,
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rMask, gMask, bMask);
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}
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else // transparency == Transparency_Alpha
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{
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alpha = InitAlpha(image, x, y);
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}
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}
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switch ( transparency )
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{
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case Transparency_Alpha:
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*alpha++ = a;
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// fall through
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case Transparency_None:
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*ptrDst++ = r;
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*ptrDst++ = g;
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*ptrDst++ = b;
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break;
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case Transparency_Mask:
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// if we couldn't find a unique colour for the mask, we
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// can have real pixels with the same value as the mask
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// and it's better to slightly change their colour than
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// to make them transparent
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if ( r == rMask && g == gMask && b == bMask )
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{
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r++;
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}
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*ptrDst++ = rMask;
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*ptrDst++ = bMask;
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*ptrDst++ = gMask;
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}
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}
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}
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}
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if ( transparency == Transparency_Mask )
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{
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image->SetMaskColour(rMask, gMask, bMask);
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}
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}
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// temporarily disable the warning C4611 (interaction between '_setjmp' and
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// C++ object destruction is non-portable) - I don't see any dtors here
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#ifdef __VISUALC__
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#pragma warning(disable:4611)
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#endif /* VC++ */
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bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose, int WXUNUSED(index) )
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bool
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wxPNGHandler::LoadFile(wxImage *image,
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wxInputStream& stream,
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bool verbose,
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int WXUNUSED(index))
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{
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// VZ: as this function uses setjmp() the only fool proof error handling
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// method is to use goto (setjmp is not really C++ dtors friendly...)
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unsigned char **lines;
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unsigned int i;
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png_infop info_ptr = (png_infop) NULL;
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unsigned char **lines = NULL;
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png_infop info_ptr = (png_infop) NULL;
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wxPNGInfoStruct wxinfo;
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wxinfo.verbose = verbose;
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@ -171,7 +476,7 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
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(png_error_ptr) NULL,
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(png_error_ptr) NULL );
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if (!png_ptr)
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goto error_nolines;
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goto error;
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png_set_error_fn(png_ptr, (png_voidp)NULL, wx_png_error, wx_png_warning);
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@ -181,16 +486,13 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
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info_ptr = png_create_info_struct( png_ptr );
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if (!info_ptr)
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goto error_nolines;
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goto error;
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if (setjmp(wxinfo.jmpbuf))
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goto error_nolines;
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goto error;
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if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
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goto error_nolines;
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png_uint_32 width,height;
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int bit_depth,color_type,interlace_type;
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png_uint_32 i, width, height;
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int bit_depth, color_type, interlace_type;
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png_read_info( png_ptr, info_ptr );
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png_get_IHDR( png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, (int*) NULL, (int*) NULL );
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@ -211,11 +513,11 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
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image->Create( (int)width, (int)height );
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if (!image->Ok())
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goto error_nolines;
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goto error;
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lines = (unsigned char **)malloc( (size_t)(height * sizeof(unsigned char *)) );
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if (lines == NULL)
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goto error_nolines;
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if ( !lines )
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goto error;
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for (i = 0; i < height; i++)
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{
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@ -227,87 +529,20 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
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}
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}
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// loaded successfully!
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{
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int transp = 0;
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png_read_image( png_ptr, lines );
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png_read_end( png_ptr, info_ptr );
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png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL );
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unsigned char *ptr = image->GetData();
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if ((color_type == PNG_COLOR_TYPE_GRAY) ||
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(color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
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{
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for (unsigned int y = 0; y < height; y++)
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{
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unsigned char *ptr2 = lines[y];
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for (unsigned int x = 0; x < width; x++)
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{
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unsigned char r = *ptr2++;
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unsigned char a = *ptr2++;
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if (a < 128)
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{
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*ptr++ = 255;
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*ptr++ = 0;
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*ptr++ = 255;
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transp = 1;
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}
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else
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{
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*ptr++ = r;
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*ptr++ = r;
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*ptr++ = r;
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}
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}
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}
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}
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else
|
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{
|
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for (unsigned int y = 0; y < height; y++)
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{
|
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unsigned char *ptr2 = lines[y];
|
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for (unsigned int x = 0; x < width; x++)
|
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{
|
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unsigned char r = *ptr2++;
|
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unsigned char g = *ptr2++;
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unsigned char b = *ptr2++;
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unsigned char a = *ptr2++;
|
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if (a < 128)
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{
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*ptr++ = 255;
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*ptr++ = 0;
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*ptr++ = 255;
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transp = 1;
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}
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else
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{
|
||||
if ((r == 255) && (g == 0) && (b == 255)) r = 254;
|
||||
*ptr++ = r;
|
||||
*ptr++ = g;
|
||||
*ptr++ = b;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
png_read_image( png_ptr, lines );
|
||||
png_read_end( png_ptr, info_ptr );
|
||||
png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL );
|
||||
|
||||
for ( unsigned int j = 0; j < height; j++ )
|
||||
free( lines[j] );
|
||||
free( lines );
|
||||
// loaded successfully, now init wxImage with this data
|
||||
CopyDataFromPNG(image, lines, width, height, color_type);
|
||||
|
||||
if (transp)
|
||||
{
|
||||
image->SetMaskColour( 255, 0, 255 );
|
||||
}
|
||||
else
|
||||
{
|
||||
image->SetMask( FALSE );
|
||||
}
|
||||
}
|
||||
for ( i = 0; i < height; i++ )
|
||||
free( lines[i] );
|
||||
free( lines );
|
||||
|
||||
return TRUE;
|
||||
|
||||
error_nolines:
|
||||
lines = NULL; // called from before it was set
|
||||
error:
|
||||
error:
|
||||
if (verbose)
|
||||
wxLogError(_("Couldn't load a PNG image - file is corrupted or not enough memory."));
|
||||
|
||||
@ -334,6 +569,10 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
|
||||
return FALSE;
|
||||
}
|
||||
|
||||
// ----------------------------------------------------------------------------
|
||||
// writing PNGs
|
||||
// ----------------------------------------------------------------------------
|
||||
|
||||
bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
|
||||
{
|
||||
wxPNGInfoStruct wxinfo;
|
||||
@ -428,16 +667,6 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
|
||||
#pragma warning(default:4611)
|
||||
#endif /* VC++ */
|
||||
|
||||
bool wxPNGHandler::DoCanRead( wxInputStream& stream )
|
||||
{
|
||||
unsigned char hdr[4];
|
||||
|
||||
if ( !stream.Read(hdr, WXSIZEOF(hdr)) )
|
||||
return FALSE;
|
||||
|
||||
return memcmp(hdr, "\211PNG", WXSIZEOF(hdr)) == 0;
|
||||
}
|
||||
|
||||
#endif // wxUSE_STREAMS
|
||||
|
||||
#endif // wxUSE_LIBPNG
|
||||
|
||||
Loading…
Reference in New Issue
Block a user